SECTION 6C1 - 3.2L ENGINE DRIVEABILITY AND

EMISSIONS (6VD1 MODELS)

SPECIFICATION

TIGHTENING SPECIFICATIONS

DIAGRAMS AND SCHEM ATICS

ECM WIRING DIAGRAM (1 OF 6)

ECM WIRING DIAGRAM (2 OF 6)

ECM WIRING DIAGRAM (3 OF 6)

ECM WIRING DIAGRAM (4 OF 6)

ECM WIRING DIAGRAM (5 OF 6)

ECM WIRING DIAGRAM (6 OF 6)

ECM PINOUTS

ECM PINOUT TABLE, 40-WAY CONNECTOR – “A”

ECM PINOUT TABLE, 40-WAY CONNECTOR – “B”

COMPONENT LOCATORS

ENGINE COMPONENT LOCATOR

ENGINE COMPONENT LOCATOR TABLE

UNDERCARRIAGE COMPONENT LOCATOR

UNDERCARRIAGE COMP ONENT

LOCATOR TABLE

SENSORS AND MISCELLANEOUS COMPONENT

LOCATORS

FUSE AND RELAY PANEL (UNDERHOOD

ELECTRICAL CENTER)

DIAGNOSIS

STRATEGY-BASED DIAGNOSTICS

DTC STORED

NO DTC

NO MATCHING SYMPTOM

INTERMITTENTS

NO TROUBLE FOUND

VERIFYING VEHICLE REPAIR

GENERAL SERVICE INFORMATION

MAITENANCE SCHEDULE

VISUAL/PHYSICAL ENGINE COMPARTMENT

INSPECTION

BASIC KNOWLEDGE OF TOOLS REQUIRED

SERAL DATA COMMUNICATIONS

CLASS II SERIAL DATA COMMUNICATIONS

ON-BOARD DIAGNOSTIC (OBD)

ON-BOARD DIAGNOSTIC TESTS

COMPREHENSIVE COMPONENT MONITOR

DIAGNOSTIC OPERATION

SYSTEM STATUS AND DRIVE CYCLE FOR

SATISFYING FEDERAL INSPECTION /

MAINTENANCE (I/M 240) REGULATIONS

COMMON OBD TERMS

THE DIAGNOSTIC EXECUTIVE

DTC TYPES

VERIFYING VEHICLE REPAIR

READING FLASH DIAGNOSTIC TROUBLE CODES

READING DIAGNOSTIC TROUBLE CODES USING A

TECH 2

ON-BOARD DIAGNOSIS (SELF-DIAGNOSIS)

TECH 2 SCAN TOOL

GETTING STARTED

OPERATING PROCEDURE

DTC MODES

DTC INFORMATION MODE

PRIMARY SYSTEM-BASED DIAGNOSTICS

FUEL CONTROL HEATED OXYGEN SENSORS

HO2S HEATER

FUEL TRIM SYSTEM MONITOR DIAGNOSTIC

OPERATION

ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK

A/C CLUTCH CONTROL CIRCUIT DIAGNOSIS

ELECTRONIC IGNITION SYSTEM DIAGNOSIS

VISUAL CHECK OF THE EVAPORATIVE EMISSION

CANISTER

FUEL METERING SYSTEM CHECK

IDLE AIR CONTROL (IAC) VALVE

FUEL SYSTEM PRESSURE TEST

FUEL INJECTOR COIL TEST PROCEDURE AND FUEL

INJECTOR BALANCE TEST PROCEDURE

ENGINE CONTROL MODULE ECM DI AGNOSIS

MULTIPLE ECM INFORMATION SENSOR DTCS

TECH 2 DATA DEFINITIONS AND RANGES

TYPICAL SCAN DATA VALUES

NO MALFUNCTION INDICATOR LAMP (MIL)

MALFUNCTION INDICATOR LAMP (MIL) “ON” STEADY

ENGINE CRANKS BUT WILL NOT RUN

FUEL SYSTEM ELECTRICAL TEST

FUEL SYSTEM DIAGNOSIS

IDLE AIR CONTROL (IAC) SYSTEM CHECK

BAROMETRIC PRESSURE (BARO) OUTPUT CHECK

ECM DIAGNOSTIC TROUBLE CODES

P0101 MAF SYSTEM PERFORMANCE

P0102 MAF SENSOR CIRCUIT LOW FREQUENCY

P0103 MAF SENSOR CIRCUIT HIGH FREQUENCY

P0107 BARO SENSOR CIRCUIT LOW VOLTAGE

P0108 BARO SENSOR CIRCUIT HIGHT VOLTAGE

P0112 IAT SENSOR CIRCUIT LOW VOLTAGE

P0113 IAT SENSOR CIRCUIT HIGH VOLTAGE

P0117 ECT SENSOR CIRCUIT LOW VOLTAGE

P0118 ECT SENSOR CIRCUIT HIGH VOLTAGE

P0121 TP SYSTEM PERFORMANCE

P0122 TP SENSOR CIRCUIT LOW VOLTAGE

P0123 TP SENSOR CIRCUIT HIGH VOLTAGE

Techline

P0131 HO2S CIRCUIT LOW VOLTAGE

P0132 HO2S CIRCUIT HIGH VOLTAGE

P0134 HO2S CIRCUIT INSUFFICIENT ACTIVITY

P0171 FUEL TRIM SYSTEM TOO LEAN

P0172 FUEL TRIM SYSTEM RICH

P0201 INJECTOR 1 CONTROL CIRCUIT

P0202 INJECTOR 2 CONTROL CIRCUIT

P0203 INJECTOR 3 CONTROL CIRCUIT

P0204 INJECTOR 4 CONTROL CIRCUIT

P0205 INJECTOR 5 CONTROL CIRCUIT

P0206 INJECTOR 6 CONTROL CIRCUIT

P0336 CKP REFERENCE SIGNAL CIRCUIT

P0337 CKP SENSOR CIRCUIT LOW FREQUENCY

P0341 CMP SENSOR CIRCUIT PERFORMAMCE

P0342 CMP SENSOR CIRCUIT LOW

P0351 IGNITION 1 CONTROL CIRCUIT

P0352 IGNITION 2 CONTROL CIRCUIT

P0353 IGNITION 3 CONTROL CIRCUIT

P0354 IGNITION 4 CONTROL CIRCUIT

P0355 IGNITION 5 CONTROL CIRCUIT

P0356 IGNITION 6 CONTROL CIRCUIT

P0502 VSS NO SIGNAL

P0562 SYSTEM VOLTAGE LOW

P0563 SYSTEM VOLTAGE HIGH

P0601 ECM MEMORY

P1171 FUEL SYSTEM LEAN DUEING

ACCELERATION

P1508 IAC SYSTEM LOW RPM

P1509 IAC SYSTEM HIGH RPM

P1626 - NO RESPONSE FROM IMMOBILISER

P1631 - RECEIVED RESPONSE WAS NOT CORRECT

P1648 RECEIVED INCORRECT SECURITY CODE

P1649 SECURITY CODE & SECURITY KEY NOT

PROGRAMMED

SYMPTOM DIAGNOSIS

DEFAULT MATRIX TABLE

CAMSHAFT POSITION (CMP) SENSOR

CRANKSHAFT POSITION (CKP) SENSOR

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

HEATED OXYGEN SENSOR (HO2S)

INTAKE AIR TEMPERATURE (IAT) SENSOR

MASS AIR FLOW (MAF) SENSOR

BAROMETRIC PRESSURE (BARO) SENSOR

MALFUNCTION INDICATOR LAMP (MIL)

ENGINE CONTROL MODULE (ECM)

EEPROM

POWER STEERING PRESSURE (PSP) SWITCH

THROTTLE POSITION (TP) SENSOR

VEHICLE SPEED SENSOR (VSS)

AIR CLEANER/AIR FILTER

IDLE AIR CONTROL (IAC) VALVE

COMMON CHAMBER

ACCELERATOR CABLE ASSEMBLY

ACCELERATOR PEDAL REPLACEMENT

FUEL FILLTER CAP

FUEL FILTER

FUEL GAUGE UNIT

FUEL INJECTORS

FUEL PRESSURE REGULATOR

FUEL METERING SYSTEM

FUEL PUMP ASSEMBLY

FUEL PUMP RELAY

FUEL RAIL ASSEMBLY

FUEL TANK

THROTTLE BODY (TB)

ELECTRONIC IGNITION SYSTEM

CATALYTIC CONVERTER

AIR CONDITIONING RELAY

EVAP CANISTER HOSES

EVAP CANISTER

EVAP CANISTER PURGE SOLENOID

FUEL TANK VENT VALVE

POSITIVE CRANKCASE VENTILATION (PCV) VALVE

WIRING AND CONNECTORS

WIRE HARNESS REPAIR: TWISTED SHIELDED CABLE

TWISTED LEADS

WEATHER-PACK CONNECTOR

COM-PACK III

METRI-PACK

GENERAL DESCRIPTION (ECM AND SENSORS)

GENERAL DESCRIPTION (AIR INDUCTION)

GENERAL DESCRIPTION (FUEL METERING)

GENERAL DESCRIPTION (ELECTRONIC IGNITION

SYSTEM)

A/C CLUTCH DIAGNOSIS

GENERAL DESCRIPTION (EVAPORATIVE (EVAP)

EMISSION SYSTEM)

DIAGNOSIS

SPECIAL TOOLS

Specification

Tightening Specifications

Application N·m Kg·m Lb Ft. Lb In.

Camshaft Position Sensor Retaining Screw 9 0.9 — 78

Crankshaft Position Sensor Mounting Bolt 9 0.9 — 78

Engine Coolant Temperature Sensor 30 3.1 22 —

Fuel Pressure Regulator Attaching Screw 6.5 0.7 — 56

Fuel Rail Bolts 7 0.7 — 61

Heated Oxygen Sensor 55 5.6 41 —

Lower Intake Manifold to Engine Block Nuts 25 2.6 18 —

Spark Plugs 18 1.8 13 —

Throttle Body Mounting Bolts 13 1.3 —113

Upper Intake Manifold to Lower Intake Manifold

Bolts 25 2.5 18 —

VSS Retaining Bolt 13 1.3 —113

Engine Control Module Bolts 10 1.0 — 87

Mass Air Flow Sensor Screw 1.5 0.15 — 13

Diagrams and Schematics

ECM Wiring Diagram (1 of 6)

060RW038

ECM Wiring Diagram (2 of 6)

060RW039

ECM Wiring Diagram (3 of 6)

060RW036

ECM Wiring Diagram (4 of 6)

060RW037

ECM Wiring Diagram (5 of 6)

060RW040

ECM Wiring Diagram (6 of 6)

060RW041

ECM Pinouts

ECM Pinout Table, 40-Way Connector – “A”

060RW043

PIN PIN Function PIN PIN Function

A1 — A21 Engine coolant temp sensor

A2 — A22 Ground

A3 — A23 Crank Angle Sensor

A4 Ground (Case) A24 Power Supply

A5 — A25 Ground (CA)

A6 — A26 —

A7 Ground (Ecu) A27 —

A8 Ground (Ecu) A28 Self Shut Off

A9 — A29 —

A10 — A30 Ignition Coil 5

A11 — A31 Ignition Coil 3

A12 — A32 Ignition Coil 1

A13 — A33 Ground (Power)

A14 — A34 Fuel Infector 5

A15 — A35 Fuel Infector 3

A16 — A36 Fuel Infector 1

A17 — A37 Ground (Case)

A18 — A38 —

A19 Intake Air Temp Sensor A39 —

A20 Barometric Pressure Sensor A40 —

ECM Pinout Table, 40-Way Connector – “B”

060RW043

PIN PIN Function PIN PIN Function

B1 — B21 Oxygen Sensor (O2 Sensor)

B2 — B22 Ground (For IGM, LAO only)

B3 Fuel Infector 2 B23 —

B4 Fuel Infector 4 B24 —

B5 Fuel Infector 6 B25 Diag

B6 Ground (Power) B26 Throttle Position Sensor (TPS)

B7 Ignition Coil 2 B27 CAM/TPS/Power Supply

B8 Ignition Coil 4 B28 Cam Angle Sensor

B9 Ignition Coil 6 B29 INH

B10 TW70 B30 P/St Pressure Switch

B11 A/C Clutch Relay B31 A/C Request

B12 Tachcmeter Signal B32 Vehicle Speed Sensor

B13 Idle Air Control Motor 1 B33 Ignition Swich

B14 Idle Air Control Motor 2 B34 Back Up Power Supply

B15 Canister Purge Solenoid (For IGM, LAO only) B35 Torque Management

B16 Idle Air Control Motor 3 B36 Power Supply

B17 Idle Air Control Motor 4 B37 Power Supply

B18 MIL Lamp B38 J1850

B19 Fuel Pump Relay B39 Ground (CAM/TPS/MAF)

B20 MAF (Air Flow Sensor) B40 —

Component Locators

Engine Component Locator

060RW061

Engine Component Locator Table

Number Name Location

1Engine Control Modul On the Common Chamber

2Throttle Position (TP) Sensor On the right of the throttle body

3Intake Air Temperature (IAT) Sensor On the intake air duct near the throttle body

4Check Engine (MIL) Light On the instrument panel beneath the

tachometer

5Positive Crankcase Ventilator (PCV) Valve On the left of the cylinder head cover

6Air Cleaner Left front of the engine bay

7Mass Air Flow (MAF) Sensor Attached to the air filter box

8Camshaft Position (CMP) Sensor On the rear right side at the left of the cylinder

head cover

9Fuel Pressure Regulator Rear right side of the engine

10 Idle Air Control (IAC) Valve On the left of the throttle body

11 Common Chamber Top of the engine

12 EVAP Canister Purge Valve Bolted to the front of the coolant pipe

13 Fuse/Relay Box Along the inside of the right fender

14 Barometric Pressure (BARO) Sensor Along the inside of the right fender

15 Throttle Body Between the intake air duct and the upper

intake manifold

16 Engine Coolant Temperature Sensor On the coolant crossover pipe at the front of

the engine, near the throttle body

Undercarriage Component Locator

060RW060

Undercarriage Component Locator Table

Number Name Location

1Fuel Pump Assembly Installed in the top of the fuel tank

2Fuel Gauge Unit Installed in the top of the fuel tank

3 Fuel Filter Located along the inside of the right frame rail,

ahead of the fuel tank

4Vehicle Speed Sensor (VSS) Protrudes from the transmission housing, just

ahead of the propeller shaft

5Heated Oxygen Sensor Threaded into the exhaust pipe behind the

converter

Sensors and Miscellaneous Component Locators

060RW107

T321066

014RW141

T321067

014RW125

060RW111

060RW024

041RW013

060RW109

060RW023

060RW050

060RW029

Fuse and Relay Panel (Underhood Electrical Center)

060RW027

Diagnosis

Strategy-Based Diagnostics

The strategy-based diagnostic is a uniform approach to

repair all Electrical/Electronic (E/E) systems. The

diagnostic flow can always be used to resolve an E/E

system problem and is a starting point when repairs are

necessary. The following steps will instruct the technician

how to proceed with a diagnosis:

1.Verify the customer complaint.

DTo verify the customer complaint, the technician

should know the normal operation of the system.

2.Perform preliminary checks.

DConduct a thorough visual inspection.

DReview the service history.

DDetect unusual sounds or odors.

DGather diagnostic trouble code information to

achieve an effective repair.

3.Check bulletins and other service information.

DThis includes videos, newsletters, etc.

4.Refer to service information (manual) system

check(s).

D“System checks” contain information on a system

that may not be supported by one or more DTCs.

System checks verify proper operation of the

system. This will lead the technician in an

organized approach to diagnostics.

5.Refer to service diagnostics.

DTC Stored

Follow the designated DTC chart exactly to make an

effective repair.

No DTC

Select the symptom from the symptom tables. Follow the

diagnostic paths or suggestions to complete the repair.

You may refer to the applicable component/system check

in the system checks.

No Matching Symptom

1.Analyze the complaint.

2.Develop a plan for diagnostics.

3.Utilize the wiring diagrams and the theory of

operation.

Call technical assistance for similar cases where repair

history may be available. Combine technician knowledge

with efficient use of the available service information.

Intermittents

Conditions that are not always present are called

intermittents. To resolve intermittents, perform the

following steps:

1.Observe history DTCs, DTC modes, and freezeframe

data.

2.Evaluate the symptoms and the conditions described

by the customer.

3.Use a check sheet or other method to identify the

circuit or electrical system component.

4.Follow the suggestions for intermittent diagnosis

found in the service documentation.

Most scan tools, such as the Tech 2 and the J

39200:DVM, have data-capturing capabilities that can

assist in detecting intermittents.

No Trouble Found

This condition exists when the vehicle is found to operate

normally. The condition described by the customer may

be normal. Verify the customer complaint against another

vehicle that is operating normally. The condition may be

intermittent. Verify the complaint under the conditions

described by the customer before releasing the vehicle.

1.Re-examine the complaint.

When the complaint cannot be successfully found or

isolated, a re-evaluation is necessary. The complaint

should be re-verified and could be intermittent as

defined in

Intermittents

, or could be normal.

2.Repair and verify.

After isolating the cause, the repairs should be made.

Validate for proper operation and verify that the

symptom has been corrected. This may involve road

testing or other methods to verify that the complaint

has been resolved under the following conditions:

DConditions noted by the customer.

DIf a DTC was diagnosed, verify a repair by

duplicating conditions present when the DTC was

set as noted in the Failure Records or Freeze

Frame data.

Verifying Vehicle Repair

Verification of the vehicle repair will be more

comprehensive for vehicles with OBD system

diagnostics. Following a repair, the technician should

perform the following steps:

IMPORTANT:Follow the steps below when you verify

repairs on OBD systems. Failure to follow these steps

could result in unnecessary repairs.

1. Review and record the Failure Records and the

Freeze Frame data for the DTC which has been

diagnosed (Freeze Frame data will only be stored for

an A or B type diagnostic and only if the MIL (“Check

Engine” lamp) has been requested).

2. Clear the DTC(s).

3. Operate the vehicle within conditions noted in the

Failure Records and Freeze Frame data.

4. Monitor the DTC status information for the specific

DTC which has been diagnosed until the diagnostic

test associated with that DTC runs.

General Service Information

Fuel Quality

Fuel quality is not a new issue for the automotive industry ,

but its potential for turning on the MIL (“Check Engine”

lamp) with OBD systems is new.

Fuel additives such as “dry gas” and “octane enhancers”

may affect the performance of the fuel. The Reed Vapor

Pressure of the fuel can also create problems in the fuel

system, especially during the spring and fall months when

severe ambient temperature swings occur. A high Reed

V apor Pressure could show up as a Fuel Trim DTC due to

excessive canister loading. High vapor pressures

generated in the fuel tank can also affect the Evaporative

Emission diagnostic as well.

Using fuel with the wrong octane rating for your vehicle

may cause driveability problems. Many of the major fuel

companies advertise that using “premium” gasoline will

improve the performance of your vehicle. Most premium

fuels use alcohol to increase the octane rating of the fuel.

Although alcohol-enhanced fuels may raise the octane

rating, the fuel’s ability to turn into vapor in cold

temperatures deteriorates. This may affect the starting

ability and cold driveability of the engine.

Low fuel levels can lead to fuel starvation, lean engine

operation, and eventually engine misfire.

Non-OEM Parts

All of the OBD diagnostics have been calibrated to run

with OEM parts.

Aftermarket electronics, such as cellular phones,

stereos, and anti-theft devices, may radiate EMI into the

control system if they are improperly installed. This may

cause a false sensor reading and turn on the MIL (“Check

Engine” lamp).

Environment

Temporary environmental conditions, such as localized

flooding, will have an effect on the vehicle ignition system.

If the ignition system is rain-soaked, it can temporarily

cause engine misfire and turn on the MIL (“Check Engine”

lamp).

Vehicle Marshaling

The transportation of new vehicles from the assembly

plant to the dealership can involve as many as 60 key

cycles within 5Km miles of driving. This type of operation

contributes to the fuel fouling of the spark plugs and will

turn on the MIL (“Check Engine” lamp).

Poor Vehicle Maintenance

The sensitivity of OBD diagnostics will cause the MIL

(“Check Engine” lamp) to turn on if the vehicle is not

maintained properly. Restricted air filters, fuel filters, and

crankcase deposits due to lack of oil changes or improper

oil viscosity can trigger actual vehicle faults that were not

previously monitored prior to OBD. Poor vehicle

maintenance can not be classified as a “non-vehicle

fault”, but with the sensitivity of OBD diagnostics, vehicle

maintenance schedules must be more closely followed.

Severe Vibration

The Misfire diagnostic measures small changes in the

rotational speed of the crankshaft. Severe driveline

vibrations in the vehicle, such as caused by an excessive

amount of mud on the wheels, can have the same effect

on crankshaft speed as misfire.

Related System Faults

Many of the OBD system diagnostics will not run if the

ECM detects a fault on a related system or component.

One example would be that if the ECM detected a Misfire

fault, the diagnostics on the catalytic converter would be

suspended until Misfire fault was repaired. If the Misfire

fault was severe enough, the catalytic converter could be

damaged due to overheating and would never set a

Catalyst DTC until the Misfire fault was repaired and the

Catalyst diagnostic was allowed to run to completion. If

this happens, the customer may have to make two trips to

the dealership in order to repair the vehicle.

Maitenance Schedule

Refer to the

Maintenance Schedule

Visual/Physical Engine Compartment

Inspection

Perform a careful visual and physical engine

compartment inspection when performing any diagnostic

procedure or diagnosing the cause of an emission test

failure. This can often lead to repairing a problem without

further steps. Use the following guidelines when

performing a visual/physical inspection:

DInspect all vacuum hoses for punches, cuts,

disconnects, and correct routing.

DInspect hoses that are difficult to see behind other

components.

DInspect all wires in the engine compartment for proper

connections, burned or chafed spots, pinched wires,

contact with sharp edges or contact with hot exhaust

manifolds or pipes.

Basic Knowledge of Tools Required

NOTE: Lack of basic knowledge of this powertrain when

performing diagnostic procedures could result in an

incorrect diagnosis or damage to powertrain

components. Do not attempt to diagnose a powertrain

problem without this basic knowledge.

A basic understanding of hand tools is necessary to effec-

tively use this section of the Service Manual.

Seral Data Communications

Class II Serial Data Communications

This vehicle utilizes the “Class II” communication system.

Each bit of information can have one of two lengths: long

or short. This allows vehicle wiring to be reduced by

transmitting and receiving multiple signals over a single

wire. The messages carried on Class II data streams are

also prioritized. If two messages attempt to establish

communications on the data line at the same time, only

the message with higher priority will continue. The device

with the lower priority message must wait. The most

significant result of this regulation is that it provides Tech 2

manufacturers with the capability to access data from any

make or model vehicle that is sold.

The data displayed on the other Tech 2 will appear the

same, with some exceptions. Some scan tools will only

be able to display certain vehicle parameters as values

that are a coded representation of the true or actual value.

For more information on this system of coding, refer to

Decimal/Binary/Hexadecimal Conversions.

On this

vehicle the Tech 2 displays the actual values for vehicle

parameters. It will not be necessary to perform any

conversions from coded values to actual values.

On-Board Diagnostic (OBD)

On-Board Diagnostic Tests

A diagnostic test is a series of steps, the result of which is

a pass or fail reported to the diagnostic executive. When

a diagnostic test reports a pass result, the diagnostic

executive records the following data:

DThe diagnostic test has been completed since the last

ignition cycle.

DThe diagnostic test has passed during the current

ignition cycle.

DThe fault identified by the diagnostic test is not

currently active.

When a diagnostic test reports a fail result, the diagnostic

executive records the following data:

DThe diagnostic test has been completed since the last

ignition cycle.

DThe fault identified by the diagnostic test is currently

active.

DThe fault has been active during this ignition cycle.

DThe operating conditions at the time of the failure.

Remember, a fuel trim DTC may be triggered by a list of

vehicle faults. Make use of all information available (other

DTCs stored, rich or lean condition, etc.) when

diagnosing a fuel trim fault.

Comprehensive Component Monitor

Diagnostic Operation

Input Components:

Input components are monitored for circuit continuity and

out-of-range values. This includes rationality checking.

Rationality checking refers to indicating a fault when the

signal from a sensor does not seem reasonable,

i.e.Throttle Position (TP) sensor that indicates high

throttle position at low engine loads or BARO voltage.

Input components may include, but are not limited to the

following sensors:

DVehicle Speed Sensor (VSS)

DInlet Air Temperature (IAT) Sensor

DCrankshaft Position (CKP) Sensor

DThrottle Position (TP) Sensor

DEngine Coolant Temperature (ECT) Sensor

DCamshaft Position (CMP) Sensor

DBarometric Pressure (BARO) Sensor

DMass Air Flow (MAF) Sensor

In addition to the circuit continuity and rationality check

the ECT sensor is monitored for its ability to achieve a

steady state temperature to enable closed loop fuel

control.

Output Components:

Output components are diagnosed for proper response to

control module commands. Components where

functional monitoring is not feasible will be monitored for

circuit continuity and out-of-range values if applicable.

Output components to be monitored include, but are not

limited to, the following circuit:

DIdle Air Control (IAC) Motor

DControl module controlled EVAP Canister Purge Valve

DElectronic Transmission controls

DA/C relays

DCooling fan relay

DVSS output

DMIL control

Refer to ECM and Sensors in General Descriptions.

Passive and Active Diagnostic Tests

A passive test is a diagnostic test which simply monitors a

vehicle system or component. Conversely , an active test,

actually takes some sort of action when performing

diagnostic functions, often in response to a failed passive

test.

Intrusive Diagnostic Tests

This is any on-board test run by the Diagnostic

Management System which may have an effect on

vehicle performance or emission levels.

Warm-Up Cycle

A warm-up cycle means that engine at temperature must

reach a minimum of 70°C (160°F)

and

rise at least 22°C

(40°F) over the course of a trip.

Freeze Frame

Freeze Frame is an element of the Diagnostic

Management System which stores various vehicle

information at the moment an emissions-related fault is

stored in memory and when the MIL is commanded on.

These data can help to identify the cause of a fault. Refer

Storing And Erasing Freeze Fame Data

for more

detailed information.

Failure Records

Failure Records data is an enhancement of the OBD

Freeze Frame feature.Failure Records store the same

vehicle information as does Freeze Frame, but it will store

that information for any fault which is stored in on-board

memory, while Freeze Frame stores information only for

emission-related faults that command the MIL on.

System Status and Drive Cycle for

Satisfying Federal Inspection/Maintenance

(I/M 240) Regulations

I/M Ready Status means a signal or flag for each

emission system test that had been set in the ECM. I/M

Ready Status indicates that the vehicle on-board

emissions diagnostics have been run. I/M Ready Status

is not concerned whether the emission system passed or

failed the test, only that on-board diagnosis is complete.

Not all vehicle use all possible I/M flags.

Common OBD Terms

Diagnostic

When used as a noun, the word diagnostic refers to any

on-board test run by the vehicle’s Diagnostic

Management System. A diagnostic is simply a test run on

a system or component to determine if the system or

component is operating according to specification. There

are many diagnostics, shown in the following list:

DOxygen sensors

Enable Criteria

The term “enable criteria” is engineering language for the

conditions necessary for a given diagnostic test to run.

Each diagnostic has a specific list of conditions which

must be met before the diagnostic will run. “Enable

criteria” is another way of saying “conditions required”.

The enable criteria for each diagnostic is listed on the first

page of the DTC description under the heading

“Conditions for Setting the DTC”. Enable criteria varies

with each diagnostic, and typically includes, but is not

limited to the following items:

Dengine speed

Dvehicle speed

DECT

DMAF/BARO

Dbarometric pressure

DIAT

DTP

Dhigh canister purge

Dfuel trim

DTCC enabled

DA/C on

Trip

Technically , a trip is a key on-run-key off cycle in which all

the enable criteria for a given diagnostic are met, allowing

the diagnostic to run. Unfortunately, this concept is not

quite that simple. A trip is official when all the enable

criteria for a given diagnostic are met. But because the

enable criteria vary from one diagnostic to another, the

definition of trip varies as well. Some diagnostic are run

when the vehicle is at operating temperature, some when

the vehicle first start up; some require that the vehicle be

cruising at a steady highway speed, some run only when

the vehicle is idle; some diagnostics function with the

TCC disables. Some run only immediately following a

cold engine start-up.

A trip then, is defined as a key on-run-key off cycle in

which the vehicle was operated in such a way as to satisfy

the enables criteria for a given diagnostic, and this

diagnostic will consider this cycle to be one trip. However ,

another diagnostic with a different set of enable criteria

(which were not met) during this driving event, would not

consider it a trip. No trip will occur for that particular

diagnostic until the vehicle is driven in such a way as to

meet all the enable criteria.

The Diagnostic Executive

The Diagnostic Executive is a unique segment of

software which is designed to coordinate and prioritize

the diagnostic procedures as well as define the protocol

for recording and displaying their results. The main

responsibilities of the Diagnostic Executive are listed as

follows:

DCommanding the MIL (“Check Engine” lamp) on and

off

DDTC logging and clearing

DFreeze Frame data for the first emission related DTC

recorded

DOperating conditions Failure Records buffer, (the

number of records will vary)

DCurrent status information on each diagnostic

The Diagnostic Executive records DTCs and turns on the

MIL when emission-related faults occur. It can also turn

off the MIL if the conditions cease which caused the DTC

to set.

Diagnostic Information

The diagnostic charts and functional checks are designed

to locate a faulty circuit or component through a process

of logical decisions. The charts are prepared with the

requirement that the vehicle functioned correctly at the

time of assembly and that there are not multiple faults

present.

There is a continuous self-diagnosis on certain control

functions. This diagnostic capability is complemented by

the diagnostic procedures contained in this manual. The

language of communicating the source of the malfunction

is a system of diagnostic trouble codes. When a

malfunction is detected by the control module, a

diagnostic trouble code is set and the Malfunction

Indicator Lamp (MIL) (“Check Engine” lamp) is

illuminated.

Malfunction Indicator Lamp (MIL)

The Malfunction Indicator Lamp (MIL) looks the same as

the MIL you are already familiar with (“Check Engine”

lamp).

Basically, the MIL is turned on when the ECM detects a

DTC that will impact the vehicle emissions.

The MIL is under the control of the Diagnostic Executive.

The MIL will be turned on if an emissions-related

diagnostic test indicates a malfunction has occurred. It

will stay on until the system or component passes the

same test, for three consecutive trips, with no

emissionsrelated faults.

Extinguishing the MIL

When the MIL is on, the Diagnostic Executive will turn off

the MIL after

three consecutive

trips that a “test passed”

has been reported for the diagnostic test that originally

caused the MIL to illuminate.

Although the MIL has been turned off, the DTC will remain

in the ECM memory (both Freeze Frame and Failure

Records) until

forty(40) warm-up cycles after no faults

have been completed.

If the MIL was set by either a fuel trim or misfire-related

DTC, additional requirements must be met. In addition to

the requirements stated in the previous paragraph, these

requirements are as follows:

DThe diagnostic tests that are passed must occur with

375 RPM of the RPM data stored at the time the last

test failed.

DPlus or minus ten (10) percent of the engine load that

was stored at the time the last failed.

DSimilar engine temperature conditions (warmed up or

warming up ) as those stored at the time the last test

failed.

Meeting these requirements ensures that the fault which

turned on the MIL has been corrected.

The MIL (“Check Engine” lamp) is on the instrument

panel and has the following functions:

DIt informs the driver that a fault that affects vehicle

emission levels has occurred and that the vehicle

should be taken for service as soon as possible.

DAs a bulb and system check, the MIL will come “ON”

with the key “ON” and the engine not running. When

the engine is started, the MIL will turn “OFF.”

DWhen the MIL remains “ON” while the engine is

running, or when a malfunction is suspected due to a

driveability or emissions problem, a Powertrain

On-Board Diagnostic (OBD) System Check must be

performed. The procedures for these checks are given

in On-Board Diagnostic (OBD) System Check. These

checks will expose faults which may not be detected if

other diagnostics are performed first.

DTC Types

Each DTC is directly related to a diagnostic test. The

Diagnostic Management System sets DTC based on the

failure of the tests during a trip or trips. Certain tests must

fail two (2) consecutive trips before the DTC is set. The

following are the four (4) types of DTCs and the

characteristics of those codes:

DType A

DEmissions related

DRequests illumination of the MIL of the first trip with a

fail

DStores a History DTC on the first trip with a fail

DStores a Freeze Frame (if empty)

DStores a Fail Record

DUpdates the Fail Record each time the diagnostic

test fails

DType B

DEmissions related

D“Armed” after one (1) trip with a fail

D“Disarmed” after one (1) trip with a pass

DRequests illumination of the MIL on the

second

consecutive trip

with a fail

DStores a History DTC on the second consecutive trip

with a fail (The DTC will be armed after the first fail)

DStores a Freeze Frame on the second consecutive

trip with a fail (if empty)

DStores a Fail Record when the first test fails (not

dependent on

consecutive trip

fails)

DUpdates the Fail Record each time the diagnostic

test fails

(Some special conditions apply to misfire and fuel trim

DTCs)

DType C (if the vehicle is so equipped)

DNon-Emissions related

DRequests illumination of the Service Lamp or the

service message on the Drive Information Center

(DIC) on the

first trip

with a fail

DStores a History DTC on the

first trip

with a fail

Does not

store a Freeze Frame

DStores Fail Record when test fails

DUpdates the Fail Record each time the diagnostic

test fails

DType D (

Type D

non-emissions related are not utilized

on certain vehicle applications).

DNon-Emissions related

DDose not request illumination of any lamp

DStores a History DTC on the

first trip

with a fail

Does not

store a Freeze Frame

DStores Fail Record when test fails

DUpdates the Fail Record each time the diagnostic

test fails

Only four Fail Records can be stored. Each Fail Record

is for a different DTC. It is possible that there will not be

Fail Records for every DTC if multiple DTCs are set.

Storing and Erasing Freeze Frame Data and Failure

Records

The data captured is called Freeze Frame data. The

Freeze Frame data is very similar to a single record of

operating conditions. Whenever the MIL is illuminated,

the corresponding record of operating conditions is

recorded to the Freeze Frame buffer.

Freeze Frame data can only be overwritten with data

associated with a misfire or fuel trim malfunction. Data

from these faults take precedence over data associated

with any other fault. The Freeze Frame data will not be

erased unless the associated history DTC is cleared.

Each time a diagnostic test reports a failure, the current

engine operating conditions are recorded in the

Failure

Records

buffer. A subsequent failure will update the

recorded operating conditions. The following operating

conditions for the diagnostic test which failed

typically

include the following parameters:

DAir Fuel Ratio

DAir Flow Rate

DFuel Trim

DEngine Speed

DEngine Load

DEngine Coolant Temperature

DVehicle Speed

DTP Angle

DBARO

DInjector Base Pulse Width

DLoop Status

Intermittent Malfunction Indicator Lamp

In the case of an “intermittent” fault, the MIL (“Check

Engine” lamp) may illuminate and then (after three trips)

go “OFF”. However, the corresponding diagnostic trouble

code will be stored in the memory. When unexpected

diagnostic trouble codes appear, check for an intermittent

malfunction.

A diagnostic trouble code may reset. Consult the

“Diagnostic Aids” associated with the diagnostic trouble

code. A physical inspection of the applicable sub–system

most often will resolve the problem.

Data Link Connector (DLC)

The provision for communication with the contorl module

is the Data Link Connector (DLC). It is located at the

lower left of the instrument panel behind a small square

cover. The DLC is used to connect to a Tech 2. Some

common uses of the Tech 2 are listed below:

DIdentifying stored Diagnostic Trouble Codes (DTCs).

DClearing DTCs.

DPerforming out put control tests.

DReading serial data.

060RW046

Verifying Vehicle Repair

Verification of vehicle repair will be more comprehensive

for vehicles with OBD system diagnostic. Following a

repair , the technician should perform the following steps:

1. Review and record the Fail Records and/or Freeze

Frame data for the DTC which has been diagnosed

(Freeze Frame data will only be stored for an A or B

type diagnostic and only if the MIL has been

requested).

2. Clear DTC(s).

3. Operate the vehicle within conditions noted in the Fail

Records and/or Freeze Frame data.

4. Monitor the DTC status information for the specific

DTC which has been diagnosed until the diagnostic

test associated with that DTC runs.

Following these steps are very important in verifying

repairs on OBD systems. Failure to follow these steps

could result in unnecessary repairs.

Reading Flash Diagnostic Trouble Codes

The provision for communicating with the Engine Control

Module (ECM) is the Data Link Connector (DLC). The

DLC is located behind the lower front instrument panel. It

is used in the assembly plant to receive information in

checking that the engine is operating properly before it

leaves the plant.

The diagnostic trouble code(s) (DTCs) stored in the

ECM’s memory can be read either through a hand-held

diagnostic scanner plugged into the DLC or by counting

the number of flashes of the “Check Engine” Malfunction

Indicator Lamp (MIL) when the diagnostic test terminal of

the DLC is grounded. The DLC terminal “6” (diagnostic

request) is pulled “Low” (grounded) by jumpering to DLC

terminal “4”, which is a ground wire.

This will signal the ECM that you want to “flash” DTC(s), if

any are present. Once terminals “4” and “6” have been

connected, the ignition switch must be moved to the “ON”

position, with the engine not running. At this point, the

“Check Engine” MIL should flash DTC12 three times

consecutively.

This would be the following flash, sequence: “flash,

pause, flash-flash, long pause, flash, pause, flash-flash,

long pause, flash, pause, flash-flash”. DTC 12 indicates

that the ECM’s diagnostic system is operating. If DTC 12

is not indicated, a problem is present within the diagnostic

system itself, and should be addressed by consulting the

appropriate diagnostic chart in DRIVEABILITY AND

EMISSIONS.

Following the output of DTC 12, the “Check Engine”MIL

will indicate a DTC three times if a DTC is present, or it will

simply continue to output DTC12. If more than one DTC

three has been stored in the ECM’s memory, the DTC(s)

will be output from the lowest to the highest, with each

DTC being displayed three times.

Reading Diagnostic Trouble Codes Using

a TECH 2

The procedure for reading diagnostic trouble code(s) is to

used a diagnostic Tech 2. When reading DTC(s), follow

instructions supplied by Tech 2 manufacturer.

For the 1998 model year, Isuzu dealer service

departments will continue to use Tech 2.

Clearing Diagnostic Trouble Codes

IMPORTANT:Do not clear DTCs unless directed to do

so by the service information provided for each diagnostic

procedure. When DTCs are cleared, the Freeze Frame

and Failure Record data which may help diagnose an

intermittent fault will also be erased from memory.

If the fault that caused the DTC to be stored into memory

has been corrected, the Diagnostic Executive will begin to

count the “warm-up” cycles with no further faults

detected, the DTC will automatically be cleared from the

ECM memory.

To clear Diagnostic T rouble Codes (DTCs), use the Tech

2 “clear DTCs” or “clear information” function. When

clearing DTCs follow instructions supplied by the Tech 2

manufacturer.

When a Tech 2 is not available, DTCs can also be cleared

by disconnecting

one

of the following sources for at least

thirty (30) seconds.

NOTE: To prevent system damage, the ignition key must

be “OFF” when disconnecting or reconnecting battery

power.

DThe power source to the control module. Examples:

fuse, pigtail at battery ECM connectors etc.

DThe negative battery cable. (Disconnecting the

negative battery cable will result in the loss of other

on-board memory data, such as preset radio tuning).

On-Board Diagnosis (Self-Diagnosis)

1. The Engine Control Module (ECM) conducts a

self-test of most of the wiring and components in the

system each time the key is turned to ON, and can

detect faults in the system while the key is ON. If a

fault is detected, the ECM will store a trouble code in

memory and flash the CHECK ENGINE indicator to

alert the driver.

2. The Diagnostic Trouble Codes (DTC) can be

displayed by shorting together terminals and the Data

Link Connector (DLC) located below Instrument

Panel of drivers side.

The CHECK ENGINE indicator will flash DTC 12

three times, followed by any DTC.If several DTC are

stored, each DTC will be displayed three times. The

DTC will be displayed in numerical order. The DTC

display will continue as long as the DLC is shorted.

Some DTC can cause other DTC to be stored, It is

important to diagnose and repair the lowest

numbered DTC first before going on to the higher

numbered DTC.

060RW031

Tech 2 Scan Tool

From 98 MY, Isuzu dealer service departments are

recommended to use Tech 2. Please refer to Tech 2 user

guide.

901RW180

Legend

(1) PCMCIA Card

(2) RS 232 Loop Back Connector

(3) SAE 16/19 Adaptor

(4) DLC Cable

(5) Tech–2

Getting Started

DBefore operating the Isuzu PCMCIA card with the Tech

2, the following steps must be performed:

1. The Isuzu 98 System PCMCIA card (1) inserts into

the Tech 2 (5).

2. Connect the SAE 16/19 adapter (3) to the DLC cable

(4).

3. Connect the DLC cable to the Tech 2 (5)

4. Make sure the vehicle ignition is off.

5. Connect the Tech 2 SAE 16/19 adapter to the vehicle

DLC.

6. The vehicle ignition turns on.

7. Verify the Tech 2 power up display.

012RW105

NOTE: The RS232 Loop back connector is only to use for

diagnosis of Tech 2 and refer to user guide of the Tech 2.

Operating Procedure

The power up screen is displayed when you power up the

tester with the Isuzu systems PCMCIA card. Follow the

operating procedure below.

060RW014

060RW032

DThe following table shows, which functions are used

the available equipment versions.

F0: Diagnostic Trouble Codes

F0: Read DTC Info Ordered By Priority

F1: Clear DTC Information

F2: DTC Information

F0: History

F1: MIL SVS or Message Requested

F2: Last Test Failed

F3: Test Failed Since Code Cleared

F4: Not Ran Since Code Cleared

F5: Failed This Ignition

F3: Freeze Frame Data/Failure Record

F1: Data Display

F0: Engine Data

F2: Snapshot

F3: Miscellaneous Tests

F0: Lamps

F0: MIL

F1: Relays

F1: A/C Relay

F2: Fuel Pump Relay

F2: EVAP

F0: Canister Purge Solenoid

F3: IAC System

F0: RPM Control

F1: IAC Control

F4: Fuel System

F1: Fuel Trim Reset

DTC Modes

On OBD passenger cars there are three options available

in the Tech 2 DTC mode to display the enhanced

information available. A description of the new modes,

DTC Info and Specific DTC, follows. After selecting DTC,

the following menu appears:

DDTC Info

DClear Info

DRead DTC Info Ordered By Priority

DFreeze Frame

The following is a brief description of each of the sub

menus in DTC Info. The order in which they appear here is

alphabetical and not necessarily the way they will appear

on the Tech 2.

DTC Information Mode

Use the DTC info mode to search for a specific type of

stored DTC information. There are six choices. The

service manual may instruct the technician to test for

DTCs in a certain manner. Always follow published

service procedures.

To get a complete description of any status, press the

“Enter” key before pressing the desired F-key. For

example, pressing “Enter” then an F-key will display a

definition of the abbreviated Tech 2 status.

Fail This Ignition

This selection will display all DTCs that have failed during

the present ignition cycle.

History

This selection will display only DTCs that are stored in the

PCM’s history memory. It will not display Type B DTCs

that have not requested the MIL (“Check Engine” lamp). It

will display all type A and B DTCs that have requested the

MIL and have failed within the last 40 warm-up cycles. In

addition, it will display all type C and type D DTCs that

have failed within the last 40 warm-up cycles.

Last Test Failed

This selection will display only DTCs that have failed the

last time the test ran. The last test may have run during a

previous ignition cycle if a type A or type B DTC is

displayed. For type C and type D DTCs, the last failure

must have occurred during the current ignition cycle to

appear as Last Test Fail.

MIL SVC or Message Requested

This selection will display only DTCs that are requesting

the MIL. Type C and type D DTCs cannot be displayed

using this option. This selection will report type B DTCs

only after the MIL has been requested.

Not Run Since Code Cleared

This option will display up to 33 DTCs that have not run

since the DTCs were last cleared. Since any displayed

DTCs have not run, their condition (passing or failing) is

unknown.

Test Failed Since Code Cleared

This selection will display all active and history DTCs that

have reported a test failure since the last time DTCs were

cleared. DTCs that last failed more than 40 warm-up

cycles before this option is selected will not be displayed.

Primary System-Based Diagnostics

There are primary system-based diagnostics which

evaluate system operation and its effect on vehicle

emissions. The primary system-based diagnostics are

listed below with a brief description of the diagnostic

function:

Oxygen Sensor Diagnosis

The fuel control heated oxygen sensors are diagnosed for

the following conditions:

DInactive signal (output steady at bias voltage – approx.

450 mV)

DSignal fixed high

DSignal fixed low

If the oxygen sensor pigtail wiring, connector or terminal

are damaged, the entire oxygen sensor assembly must

be replaced. DO NOT attempt to repair the wiring,

connector or terminals. In order for the sensor to function

properly, it must have clean reference air provided to it.

This clean air reference is obtained by way of the oxygen

sensor wire(s). Any attempt to repair the wires, connector

or terminals could result in the obstruction of the

reference air and degrade oxygen sensor performance.

Refer to

On-Vehicle Service Heated Oxygen Sensors.

Fuel Control Heated Oxygen Sensors

The main function of the fuel control heated oxygen

sensors is to provide the control module with exhaust

stream oxygen content information to allow proper fueling

and maintain emissions within mandated levels. After it

reaches operating temperature, the sensor will generate

a voltage, inversely proportional to the amount of oxygen

present in the exhaust gases. The control module uses

the signal voltage from the fuel control heated oxygen

sensors while in closed loop to adjust fuel injector pulse

width. While in closed loop, the ECM can adjust fuel

delivery to maintain an air/fuel ratio which allows the best

combination of emission control and driveability . The fuel

control heated oxygen sensors are also used to

determine catalyst efficiency.

HO2S Heater

Heated oxygen sensors are used to minimize the amount

of time required for closed loop fuel control to begin

operation and to allow accurate catalyst monitoring. The

oxygen sensor heater greatly decreases the amount of

time required for fuel control sensors to become active.

Oxygen sensor heaters are required by catalyst monitor

and sensors to maintain a sufficiently high temperature

which allows accurate exhaust oxygen content readings

further away from the engine.

Fuel Trim System Monitor Diagnostic

Operation

Fuel Trim System Monitor Diagnostic

Operation

This system monitors the averages of short-term and

long-term fuel trim values. If these fuel trim values stay at

their limits for a calibrated period of time, a malfunction is

indicated. The fuel trim diagnostic compares the

averages of short-term fuel trim values and long-term fuel

trim values to rich and lean thresholds. If either value is

within the thresholds, a pass is recorded. If both values

are outside their thresholds, a rich or lean DTC will be

recorded.

The fuel trim system diagnostic also conducts an intrusive

test. This test determines if a rich condition is being

caused by excessive fuel vapor from the EVAP canister.

In order to meet OBD requirements, the control module

uses weighted fuel trim cells to determine the need to set

a fuel trim DTC. A fuel trim DTC can only be set if fuel trim

counts in the weighted fuel trim cells exceed

specifications. This means that the vehicle could have a

fuel trim problem which is causing a problem under

certain conditions (i.e., engine idle high due to a small

vacuum leak or rough idle due to a large vacuum leak)

while it operates fine at other times. No fuel trim DTC

would set (although an engine idle speed DTC or HO2S

DTC may set). Use a Tech 2 to observe fuel trim counts

while the problem is occurring.

A fuel trim DTC may be triggered by a number of vehicle

faults. Make use of all information available (other DTCs

stored, rich or lean condition, etc.) when diagnosing a fuel

trim fault.

Fuel Trim Cell Diagnostic Weights

No fuel trim DTC will set regardless of the fuel trim counts

in cell 0 unless the fuel trim counts in the weighted cells

are also outside specifications. This means that the

vehicle could have a fuel trim problem which is causing a

problem under certain conditions (i.e. engine idle high due

to a small vacuum leak or rough due to a large vacuum

leak) while it operates fine at other times. No fuel trim

DTC would set (although an engine idle speed DTC or

HO2S DTC may set). Use a Tech 2 to observe fuel trim

counts while the problem is occurring.

On-Board Diagnostic (OBD) System Check

060RW045

Circuit Description

The on-board diagnostic system check is the starting

point for any driveability complaint diagnosis. Before

using this procedure, perform a careful visual/physical

check of the ECM and engine grounds for cleanliness and

tightness.

The on-board diagnostic system check is an organized

approach to identifying a problem created by an

electronic engine control system malfunction.

Diagnostic Aids

An intermittent may be caused by a poor connection,

rubbed-through wire insulation or a wire broken inside the

insulation. Check for poor connections or a damaged

harness. Inspect the ECM harness and connector for

improper mating, broken locks, improperly formed or

damaged terminals, poor terminal-to-wire connection,

and damaged harness.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart:

1. The MIL (“Check Engine” lamp) should be “ON”

steady with the ignition “ON”/engine “OFF.” If not,

the “No Malfunction Indicator Lamp (MIL)” chart

should be used to isolate the malfunction.

2. Checks the Class 2 data circuit and ensures that the

ECM is able to transmit serial data.

3. This test ensures that the ECM is capable of

controlling the MIL (“Check Engine” lamp) and the

MIL (“Check Engine” lamp) driver circuit is not

shorted to ground.

4. If the engine will not start, the

Cranks But Will Not

Run

chart should be used to diagnose the condition.

7. A Tech 2 parameter which is not within the typical

range may help to isolate the area which is causing

the problem.

10.This vehicle is equipped with a ECM which utilizes

an electrically erasable programmable read only

memory (EEPROM).

On- Board Diagnostic (OBD) System Check

Step Action Value(s) Yes No

1 1. Ignition “ON,” engine “OFF.”

2. Observe the malfunction indicator lamp (MIL or

“Check Engine” lamp).

Is the MIL (“Check Engine” lamp)“ON?” —Go to

Step 2

Go to

No MIL

(“Check

Engine” lamp)

21. Ignition “OFF.”

2. Install a Tech 2.

3. Ignition “ON.”

4. Attempt to display ECM engine data with the T ech 2.

Does the Tech 2 display ECM data? —Go to

Step 3

Go to

Step 8

31. Using the Tech 2 output tests function, select MIL

(“Check Engine” lamp) dash lamp control and

command the MIL (“Check Engine” lamp) “OFF.”

2. Observe the MIL (“Check Engine” lamp).

Did the MIL (“Check Engine” lamp) turn “OFF?” —Go to

Step 4

Go to

MIL

(“Check

Engine” lamp)

On Steady

4Attempt to start the engine.

Did the engine start and continue to run? —Go to

Step 5

Go to

Cranks

But Will Not

Run

5Select “Display DTCs” with the Tech 2.

Are any DTCs stored? —Go to

Step 6

Go to

Step 7

6Are two or more of the following DTCs stored? P0107,

P0108, P0113, P0118, P0122, P0123.

—

Go to

“Multiple

ECM

Information

Sensor DTCs

Set”

Go to

applicable

DTC table

7Compare ECM data values displayed on the Tech 2 to

the typical engine scan data values.

Are the displayed values normal or close to the typical

values? —

Refer to

Typical scan

data value

Refer to

indicated

Component

System

Checks

81. Ignition “OFF,” disconnect the ECM.

2. Ignition “ON,” engine “OFF.”

3. Check the Class 2 data circuit for an open, short to

ground, or short to voltage. Also, check the DLC

ignition feed circuit for an open or short to ground

and the DLC ground circuit for an open.

4. If a problem is found, repair as necessary.

Was a problem found? —Go to

Step 2

Go to

Step 9

91. Attempt to reprogram the ECM. Refer to

On-Vehicle Service

Engine Control Module and

Sensors

for procedures.

2. Attempt to display ECM data with the Tech 2.

Does the Tech 2 display ECM engine data? —Go to

Step 2

Go to

Step 10

10 Replace the ECM.

Is the action complete? —Go to

Step 2

—

A/C Clutch Control Circuit Diagnosis

060RW041

Circuit Description

When air conditioning and blower fan are selected, and if

the system has a sufficient refrigerant charge, a 12-volt

signal is supplied to the A/C request input of the Engine

Control Module ECM. The A/C request signal may be

temporarily canceled during system operation by the

electronic thermostat in the evaporator case. The

electronic thermostat may intermittently remove the

control circuit ground for the A/C thermostat relay to

prevent the evaporator from forming ice. When the A/C

request signal is received by the ECM, the ECM supplies

a ground from the compressor clutch relay if the engine

operating conditions are within acceptable ranges. With

the A/C compressor relay energized, voltage is supplied

to the compressor clutch coil.

The ECM will enable the compressor clutch to engage

whenever A/C has been selected with the engine running,

unless any of the following conditions are present:

DThe throttle is greater than 90%.

DThe ignition voltage is below 10.5 volts.

DThe engine speed is greater than 4500 RPM for 5

seconds or 5400 RPM.

DThe engine coolant temperature (ECT) is greater than

125 °C (257 °F).

DThe intake air temperature (IAT) is less than 5°C

(41°F).

DThe power steering pressure switch signals a cramped

position.

Diagnostic Aids

To diagnose an the intermittent fault, check for the

following conditions:

DPoor connection at the ECM–Inspect connections for

backed-out terminals, improper mating, broken locks,

improperly formed or damaged terminals, and poor

terminal-to-wire connection.

DDamaged harness–Inspect the wiring harness for

damage. If the harness appears to OK, observe the

A/C clutch while moving connectors and wiring

harnesses related to the A/C. A sudden clutch

malfunction will indicate the source of the intermittent

fault.

A/C Clutch Diagnosis

This chart should be used for diagnosing the electrical

portion of the A/C compressor clutch circuit. A Tech 2 will

be used in diagnosing the system. The Tech 2 has the

ability to read the A/C request input to the ECM. The Tech

2 can display when the ECM has commanded the A/C

clutch “ON.” The Tech 2 should have the ability to

override the A/C request signal and energize the A/C

compressor relay.

Test Description

IMPORTANT:Do not engage the A/C compressor

clutch with the engine running if an A/C mode is not

selected at the A/C control switch.

The numbers below refer to the step numbers on the

Diagnostic Chart:

3. This a test determine is the problem is with the

refrigerant system. If the switch is open, A/C

pressure gauges will be used to determine if the

pressure switch is faulty or if the system is partially

discharged or empty.

4. Although the normal complaint will be the A/C clutch

failing to engage, it is possible for a short circuit to

cause the clutch to run when A/C has not been

selected. This step is a test for that condition.

7. There is an extremely low probability that both relays

will fail at the same time, so the substitution process

is one way to check the A/C Thermostat relay. Use

a known good relay to do a substitution check.

9. The blower system furnishes a ground for the A/C

control circuit, and it also shares a power source

through the Heater and A/C Relay. The blower

must be “ON” in order to test the A/C system.

A/C Clutch Control Circuit Diagnosis

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Are any other DTCs stored?

—

Go to the

other DTC

chart(s) first Go to

Step 3

31. Disconnect the electrical connector at the pressure

switch located on the receiver/drier.

2. Use an ohmmeter to check continuity across the

pressure switch (BRN to GRN/WHT).

Is the pressure switch open? —

Go to Air

Conditioning

to diagnose

the cause of

the open

pressure

switch Go to

Step 4

StepNoYesValue(s)Action

4IMPORTANT:Before continuing with the diagnosis, the

following conditions must be met:

DThe intake air temperature must be greater than

15°C. (60°F).

DThe engine coolant temperature must be less

than 119°C (246°F).

1. A/C “OFF.”

2. Start the engine and idle for 1 minute.

3. Observe the A/C compressor.

Is the A/C compressor clutch engaged even though

A/C has not been requested? —Go to

Step 45

Go to

Step 5

51. Idle the engine.

2. A/C “ON”.

3. Blower “ON”.

4. Observe the A/C compressor.

Is the A/C compressor magnetic clutch engaged? —

Refer to

Diagnostic

Aids

Go to

Step 6

61. Engine idling.

2. A/C “ON”.

3. Blower “ON”.

4. Observe the “A/C Request” display on the Tech 2.

Does the “A/C Request” display indicate “Yes?” —Go to

Step 34

Go to

Step 7

7Temporarily substitute the A/C compressor relay in

place of the A/C thermostat relay, then repeat Step 5.

Did the “A/C Request” display indicate “Yes?” —Go to

Step 8

Go to

Step 9

8Replace the original A/C thermostat relay.

Is the action complete? — Verify repair —

9Dose the blower operate? —Go to

Step 10

Go to

Step 11

10 Repair the blower.

Is the action complete? — Verify repair —

11 Check for a faulty 10a A/C fuse in the passenger

compartment fuse panel.

Was the 10A fuse OK? —Go to

Step 13

Go to

Step 12

12 Check for short circuit and make repairs if necessary.

Replace the 10A A/C fuse.

Is the action complete? — Verify repair —

13 1. Ignition “ON.”

2. Use a DVM to check voltage at the positive A/C

switch wire (BRN).

Was voltage equal to the specified value? B+ Go to

Step 15

Go to

Step 14

14 Repair the open wire (BRN) between the A/C switch

and the A/C fuse.

Is the action complete? — Verify repair —

Step NoYesValue(s)Action

15 1. Remove the glove box to gain access to the A/C

thermostat.

2. Disconnect the thermostat connector.

3. Attach a fused jumper between ground and the

GRN/RED wire at the thermostat.

4. A/C “ON.”

5. Blower “ON.”

Dose A/C request indicate “YES” on the Tech 2? —Go to

Step 16

Go to

Step 23

16 1. Ignition “ON.”

2. A/C switch “ON”.

3. Use a DVM to check voltage at the electronic A/C

thermostat.

Was voltage equal to the specified value? B+ Go to

Step 20

Go to

Step 17

17 Check for an open (LT GRN/BLK) wire between the

thermostat and the A/C switch.

Was the wire open? —Go to

Step 18

Go to

Step 19

18 Repair the open wire (LT GRN/BLK) between the

thermostat and the A/C switch.

Is the action complete? — Verify repair —

19 Replace the A/C switch.

Is the action complete? — Verify repair —

20 Use an ohmmeter to check continuity between the

electronic A/C thermostat and the blower switch.

Was there an open circuit? —Go to

Step 21

Go to

Step 22

21 Repair the open wire (WHT) between the thermostat

and the blower switch.

Is the action complete? — Verify repair —

22 Replace the electronic A/C thermostat.

Is the an action complete? — Verify repair —

23 Check for an open circuit between A/C thermostat relay

and ECM A/C request terminal (B-31).

Was there an open circuit? —Go to

Step 24

Go to

Step 25

24 Repair the open circuit between the ECM and A/C

thermostat relay.

Is the action complete? — Verify repair —

25 Check for an open circuit between the engine device

fuse and the A/C thermostat relay (WHT/GRN).

Was there an open circuit? —Go to

Step 26

Go to

Step 27

26 Repair the open circuit between the engine device fuse

and the A/C thermostat relay.

Is the action complete? — Verify repair —

27 1. Ignition “ON.”

2. Use a DVM to check voltage at the A/C pressure

switch (BRN).

Was voltage equal to the specified value? B+ Go to

Step 29

Go to

Step 28

Step NoYesValue(s)Action

28 Repair the open circuit between the 10A A/C fuse and

the pressure switch.

Is the action complete? — Verify repair —

29 Use an ohmmeter to check continuity between the

pressure switch and the A/C thermostat relay.

Was the circuit open? —Go to

Step 30

Go to

Step 31

30 Repair the open circuit between the pressure switch

and the A/C thermostat relay.

Is the action complete? — Verify repair —

31 Check for damaged pin or terminal at the ECM.

Was a damaged pin or terminal found? —Go to

Step 32

Go to

Step 33

32 Repair the damaged pin or terminal.

Is the action complete? — Verify repair —

33 Replace the ECM.

Is the action complete? — Verify repair —

34 1. Remove the A/C compressor relay.

2. Ignition “ON.”

3. Use a DVM to check voltage at both of the BRN

wires at the A/C compressor relay socket.

Is the voltage equal to the specified value? B+ Go to

Step 36

Go to

Step 35

35 Repair the faulty BRN wire between the A/C fuse and

the A/C compressor relay .

Is the action complete? — Verify repair —

36 1. A/C compressor relay removed.

2. Engine idling.

3. A/C “ON.”

4. Blower “ON.”

5. Use a DVM to measure voltage between the

GRY/RED wire at the A/C compressor relay socket

and battery+.

Did the DVM indicate the specified value? B+ Go to

Step 40

Go to

Step 37

37 Check for an open GRY/RED wire between ECM

terminal B-11 and the A/C compressor relay.

Was the wire open? —Go to

Step 38

Go to

Step 39

38 Repair the open GRY/RED wire between the ECM and

the A/C compressor relay.

Is the action complete? — Verify repair —

39 Check for a damaged pin or terminal at B-11 of the

ECM.

Was a damaged pin or a terminal found? —Go to

Step 32

Go to

Step 33

Step NoYesValue(s)Action

40 1. A/C compressor relay removed.

2. Connect a fused jumper at the A/C compressor

relay socket between either BRN wire and the GRN

wire.

3. Engine idling.

4. A/C “ON.”

5. Blower “ON.”

Did the compressor magnetic clutch engage? —Go to

Step 41

Go to

Step 42

41 Repair the A/C compressor relay.

Is the action complete? — Verify repair —

42 Check for an open circuit between the A/C compressor

relay and the A/C clutch.

Was an open circuit found? —Go to

Step 43

Go to

Step 44

43 Repair the open circuit between the compressor Clutch

and the A/C compressor relay.

Is the action complete? — Verify repair —

44 Service the compressor clutch or replace the

compressor due to a faulty internal overheat switch.

Is the action complete? — Verify repair —

45 1. Remove the A/C compressor relay.

2. Idle the engine.

Is the compressor clutch still engaged when A/C is not

selected? — Go to

Step 46

Go to

Step 47

46 Repair the short to voltage between the A/C clutch and

A/C compressor relay.

Is the action complete? — Verify repair —

47 1. Reinstall the A/C compressor relay.

2. Remove the A/C thermostat relay.

3. Engine idling.

Is the compressor clutch still engaged when A/C is not

selected? — Go to

Step 48

Go to

Step 50

48 Use a DVM to check for a short to ground between the

A/C compressor relay and B-11 of the ECM.

Was a short detected? —Go to

Step 49

Go to

Step 33

49 Repair the short to ground between the ECM and A/C

compressor relay.

Is the action complete? — Verify repair —

50 Repair the short to ground between the A/C thermostat

relay and the electronic thermostat.

Is the action complete? — Verify repair —

Electronic Ignition System Diagnosis

If the engine cranks but will not run or immediately stalls,

the Engine Cranks But Will Not Start chart must be used

to determine if the failure is the ignition system or the fuel

system. If DTC P0341, or P0336 is set, the appropriate

diagnostic trouble code chart must be used for diagnosis.

If a misfire is being experienced with no DTC set, refer to

the

Symptoms

section for diagnosis.

Visual Check of The Evaporative

Emission Canister

DIf the canister is cracked or damaged, replace the

canister.

DIf fuel is leaking from the canister, replace the canister

and check hoses and hose routing.

Fuel Metering System Check

Some failures of the fuel metering system will result in an

“Engine Cranks But Will Not Run” symptom. If this

condition exists, refer to the

Engine Cranks But Will Not

Run

chart. This chart will determine if the problem is

caused by the ignition system, the ECM, or the fuel pump

electrical circuit.

Refer to

Fuel System Electrical Test

for the fuel system

wiring schematic.

If there is a fuel delivery problem, refer to

Fuel System

Diagnosis

, which diagnoses the fuel injectors, the fuel

pressure regulator, and the fuel pump. If a malfunction

occurs in the fuel metering system, it usually results in

either a rich HO2S signal or a lean HO2S signal. This

condition is indicated by the HO2S voltage, which causes

the ECM to change the fuel calculation (fuel injector pulse

width) based on the HO2S reading. Changes made to the

fuel calculation will be indicated by a change in the long

term fuel trim values which can be monitored with a Tech

2. Ideal long term fuel trim values are around 0%; for a

lean HO2S signal, the ECM will add fuel, resulting in a fuel

trim value above 0%. Some variations in fuel trim values

are normal because all engines are not exactly the same.

If the evaporative emission canister purge is “ON,” the

long term fuel trim may be as low as –38%. If the fuel trim

values are greater than +23%, refer to

DTC P0131,DTC

P0171, and DTC 1171

for items which can cause a lean

HO2S signal.

Idle Air Control (IAC) Valve

The Tech 2 displays the IAC pintle position in counts. A

count of “0” indicates the ECM is commanding the IAC

pintle to be driven all the way into a fully-seated position.

This is usually caused by a large vacuum leak.

The higher the number of counts, the more air is being

commanded to bypass the throttle blade. Refer to IAC

System Check in order to diagnose the IAC system.

Refer to

Rough, Unstable, or Incorrect Idle, Stalling

Symptoms

for other possible causes of idle problems.

Fuel System Pressure Test

A fuel system pressure test is part of several of the

diagnostic charts and symptom checks. To perform this

test, refer to

Fuel Systems Diagnosis.

Fuel Injector Coil Test Procedure and

Fuel Injector Balance Test Procedure

T32003

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart:

2. Relieve the fuel pressure by connecting the

5–8840–0378–0 Fuel Pressure Gauge to the fuel

pressure connection on the fuel rail.

CAUTION:In order to reduce the risk of fire and

personal injury, wrap a shop towel around the fuel

pressure connection. The towel will absorb any fuel

leakage that occurs during the connection of the fuel

pressure gauge. Place the towel in an approved

container when the connection of the fuel pressure

gauge is complete.

Place the fuel pressure gauge bleed hose in an

approved gasoline container.

With the ignition switch “OFF,” open the valve on the

fuel pressure gauge.

3. Record the lowest voltage displayed by the DVM

after the first second of the test. (During the first

second, voltage displayed by the DVM may be

inaccurate due to the initial current surge.)

Injector Specifications:

Resistance Ohms Voltage Specification at

10°C-35°C (50°F-95°F)

11.8 – 12.6 5.7 – 6.6

DThe voltage displayed by the DVM should be within

the specified range.

DThe voltage displayed by the DVM may increase

throughout the test as the fuel injector windings

warm and the resistance of the fuel injector windings

changes.

DAn erratic voltage reading (large fluctuations in

voltage that do not stabilize) indicates an

intermittent connection within the fuel injector.

5.Injector Specifications:

Highest Acceptable

Voltage Reading

Above/Below 35°C/10°C

(95°F/50°F)

Acceptable Subtracted

Value

9.5 Volts 0.6 Volts

7.The Fuel Injector Balance Test portion of this chart

(Step 7 through Step 11) checks the mechanical

(fuel delivery) portion of the fuel injector. An engine

cool-down period of 10 minutes is necessary in

order to avoid irregular fuel pressure readings due

to “Hot Soak” fuel boiling.

Injector Coil Test Procedure (Steps 1-6) and Injector Balance Test Procedure

(Steps 7-11)

R262001

CYLINDER 1 2 3 4 5 6

1st Reading (1) 296 kpa

(43 psi) 296 kpa

(43 psi)

2nd Reading (2) 131 kpa

(19 psi) 117 kpa

(17 psi) 124 kpa

(18 psi) 145 kpa

(21 psi) 131 kpa

(19 psi) 130 kpa

(19 psi)

Amount of Drop (1st

Reading–2nd Reading) 165 kpa

(24 psi) 179 kpa

(26 psi) 172 kpa

(25 psi) 151 kpa

(22 psi) 165 kpa

(24 psi) 166 kpa

(24 psi)

Av.drop = 166 kpa/24 psi

±10 kpa/1.5 psi

= 156- 176 kpa or 22.5-

25.5 psi

OK Faulty, Rich

(Too Much

Fuel Drop)

OK Faulty, Lean

( Too Little

Fuel Drop)

OK OK

NOTE: These figures are examples only.

Injector Coil Test Procedure (Steps 1-6) and Injector Balance Test Procedure

(Steps 7-11)

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to Step 2

Go to

OBD

System

Check

2 1.Turn the engine “OFF.”

NOTE:In order to prevent flooding of a single cylinder

and possible engine damage, relieve the fuel pressure

before performing the fuel injector coil test procedure.

2.Relieve the fuel pressure. Refer to

Test Description

Number 2.

3.Connect the 5–8840–2638–0 Fuel Injector Tester to

B+ and ground, and to the 5–8840–2619–0 Injector

Switch Box.

4.Connect the injector switch box to the grey fuel

injector harness connector located at the rear of the

air cleaner assembly.

5.Set the amperage supply selector switch on the fuel

injector tester to the “Coil Test” 0.5 amp position.

6.Connect the leads from the 5–8840–0285–0 Digital

Voltmeter (DVM) to the injector tester. Refer to the

illustrations associated with the test description.

7.Set the DVM to the tenths scale (0.0).

8.Observe the engine coolant temperature.

Is the engine coolant temperature within the specified

values?

10°C (50°F)

to 35°C

(95°F) Go to

Step 3

Go to

Step 5

31.Set injector switch box injector #1.

2.Press the “Push to Start Test” button on the fuel

injector tester.

3.Observe the voltage reading on the DVM.

IMPORTANT:The voltage reading may rise during the

test.

4. Record the lowest voltage observed after the first

second of the test.

5. Set the injector switch box to the next injector and

repeat steps 2, 3, and 4.

Did any fuel injector have an erratic voltage reading

(large fluctuations in voltage that did not stabilize) or a

voltage reading outside of the specified values? 5.7-6.6 V Go to

Step 4

Go to

Step 7

4Replace the faulty fuel injector(s). Refer to

Fuel

Injector.

Is the action complete? —Go to

Step 7

—

StepNoYesValue(s)Action

51.Set injector switch box injector #1.

2.Press the “Push to Start Test” button on the fuel

injector tester.

3.Observe the voltage reading on the DVM.

IMPORTANT:The voltage reading may rise during the

test.

4.Record the lowest voltage observed after the first

second of the test.

5.Set the injector switch box to the next injector and

repeat steps 2, 3, and 4.

Did any fuel injector have an erratic voltage reading

(large fluctuations in voltage that did not stabilize) or a

voltage reading above the specified value? 9.5 V Go to

Step 4

Go to

Step 6

61.Identify the highest voltage reading recorded (other

than those above 9.5 V).

2.Subtract the voltage reading of each injector from

the highest voltage selected in step 1. Repeat until

you have a subtracted value for each injector.

For any injector, is the subtracted Value in step 2

greater than the specified value? 0.6 V Go to

Step 4

Go to

Step 7

7CAUTION:In order to reduce the risk of fire and

personal injury, wrap a shop towel around the

fuel pressure connection. The towel will absorb

any fuel leakage that occurs during the

connection of the fuel pressure gauge. Place the

towel in an approved container when the

connection of the fuel pressure gauge is

complete.

1. Connect the J 34730-1 Fuel Pressure Gauge to the

fuel pressure test port.

2. Energize the fuel pump using the Tech 2.

3. Place the bleed hose of the fuel pressure gauge into

an approved gasoline container.

4. Bleed the air out of the fuel pressure gauge.

5. With the fuel pump running, observe the reading on

the fuel pressure gauge.

Is the fuel pressure within the specified values?

296 kpa-376

kpa (43-55

psi) Go to

Step 8

Go to

Fuel

System

Diagnosis

8 Turn the fuel pump “OFF.”

Does the fuel pressure remain constant? —Go to

Step 9

Go to

Fuel

System

Diagnosis

Step NoYesValue(s)Action

91. Connect the 5–8840–2638–0 Fuel Injector Tester

and 5–8840–2619–0 Injector Switch Box the fuel

injector harness connector.

2. Set the amperage supply selector switch on the fuel

injector tester to the “Balance Test” 0.5-2.5 amp

position.

3. Using the Tech 2 turn the fuel pump “ON” then

“OFF” in order to pressurize the fuel system.

4. Record the fuel pressure indicated by the fuel

pressure gauge after the fuel pressure stabilizes.

This is the first pressure reading.

5. Energize the fuel injector by depressing the “Push

to Start Test” button on the fuel injector tester.

6. Record the fuel pressure indicated by the fuel

pressure gauge after the fuel pressure gauge

needle has stopped moving. This is the second

pressure reading.

7. Repeat steps 1 through 6 for each fuel injector.

8. Subtract the second pressure reading from the first

pressure reading for one fuel injector. The result is

the pressure drop value.

9. Obtain a pressure drop value for each fuel injector.

10.Add all of the individual pressure drop values. This

is the total pressure drop.

1 1.Divide the total pressure drop by the number of fuel

injectors. This is the average pressure drop.

Does any fuel injector have a pressure drop value that

is either higher than the average pressure drop or lower

than the average pressure drop by the specified value? 10 kpa (1.5

psi) Go to

Step 10

Go to

OBD

System

Check

10 Re-test any fuel injector that does not meet the

specification. Refer to the procedure in step 11.

NOTE: Do not repeat any portion of this test before

running the engine in order to prevent the engine from

flooding.

Does any fuel injector still have a pressure drop value

that is either higher than the average pressure drop or

lower than the average pressure drop by the specified

value? 10 kpa (1.5

psi) Go to

Step 11

Go to

Symptoms

11 Replace the faulty fuel injector(s). Refer to

Fuel

Injector.

Is the action complete? — Verify repair —

Engine Control Module ECM

Diagnosis

To read and clear diagnostic trouble codes, use a Tech 2.

IMPORTANT:Use of a Tech 2 is recommended to clear

diagnostic trouble codes from the ECM memory.

Diagnostic trouble codes can also be cleared by turning

the ignition “OFF” and disconnecting the battery power

from the ECM for 30 seconds. Turning off the ignition and

disconnecting the battery power from the ECM will cause

all diagnostic information in the ECM memory to be

cleared. Therefore, all the diagnostic tests will have to be

re-run.

Since the ECM can have a failure which may affect only

one circuit, following the diagnostic procedures in this

section will determine which circuit has a problem and

where it is.

If a diagnostic chart indicates that the ECM connections

or the ECM is the cause of a problem, and the ECM is

replaced, but this does not correct the problem, one of the

following may be the reason:

DThere is a problem with the ECM terminal connections.

The terminals may have to be removed from the

connector in order to check them properly.

DThe problem is intermittent. This means that the

problem is not present at the time the system is being

checked. In this case, refer to the

Symptoms

portion of

the manual and make a careful physical inspection of

all components and wiring associated with the affected

system.

DThere is a shorted solenoid, relay coil, or harness.

Solenoids and relays are turned “ON” and “OFF” by the

ECM using internal electronic switches called drivers.

A shorted solenoid, relay coil, or harness will not

damage the ECM but will cause the solenoid or relay to

be inoperative.

Multiple ECM Information Sensor

DTCS Set

Circuit Description

The Engine Control Module ECM monitors various

sensors to determine the engine operating conditions.

The ECM controls fuel delivery, spark advance,

transmission operation, and emission control device

operation based on the sensor inputs.

The ECM provides a sensor ground to all of the sensors.

The ECM applies 5 volts through a pull-up resistor, and

determines the status of the following sensors by

monitoring the voltage present between the 5-volt supply

and the resistor:

DThe engine coolant temperature (ETC) sensor

DThe intake air temperature (IAT) sensor

The ECM provides the following sensors with a 5-volt

reference and a sensor ground signal:

DThe throttle position (TP) sensor

DThe barometric pressure (BARO) sensor

The ECM monitors the separate feedback signals from

these sensors in order to determine their operating

status.

Diagnostic Aids

IMPORTANT:Be sure to inspect ECM and engine

grounds for being secure and clean.

A short to voltage in one of the sensor input circuits may

cause one or more of the following DTCs to be set:

DP0108

DP0113

DP0118

DP0123

IMPORTANT:If a sensor input circuit has been shorted

to voltage, ensure that the sensor is not damaged. A

damaged sensor will continue to indicate a high or low

voltage after the affected circuit has been repaired. If the

sensor has been damaged, replace it.

An open in the sensor ground circuit between the ECM

and the splice will cause one or more of the following

DTCs to be set:

DP0108

DP0113

DP0118

DP0123

A short to ground in the 5-volt reference A or B circuit will

cause one or more of the following DTCs to be set:

DP0107

DP0122

An the in the 5-volt reference circuit A, between the ECM

and the splice will cause one or more of the following

DTCs to be set:

DP0122

An the in the 5-volt reference circuit B, between the ECM

and the splice will cause one or more of the following

DTCs to be set:

DP0107

Check for the following conditions:

DPoor connection at ECM. Inspect the harness

connectors for backed-out terminals, improper mating,

broken locks, improperly formed or damage terminals,

and a poor terminal-to-wire connection.

DDamaged harness. Inspect the wiring harness for

damage. If the harness is not damaged, observe an

affected sensor’s displayed value on the Tech 2 with

the ignition “ON” and the engine “OFF” while you move

the connectors and the wiring harnesses related to the

following sensors:

DIAT

DECT

DTP

DBARO

Multiple ECM Information Sensor DTCs Set

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Turn the ignition “OFF,” disconnect the ECM.

2. T urn the ignition “ON,” check the 5 volt reference A

circuit for the following conditions:

DA poor connection at the ECM.

DAn open between the ECM connector and the

splice.

DA short to ground.

DA short to voltage.

Is there an open or short? —Go to

Step 3

Go to

Step 4

3Repair the open or short.

Is the action complete? — Verify repair —

4Check the sensor ground circuit for the following

conditions:

DA poor connection at the ECM or the affected

sensors.

DAn open between the ECM connector and the

affected sensors.

Is there an open or a poor connection? —Go to

Step 5

Go to

Step 6

5Repair the open or the poor connection.

Is the action complete? — Verify repair —

6Measure the voltage between the BARO sensor signal

circuit at the ECM harness connector and ground.

Does the voltage measure near the specified value? 0 V Go to

Step 7

Go to

Step 11

7Measure the voltage between the TP sensor signal

circuit at the ECM harness connector and ground.

Does the voltage measure near the specified value? 0 V Go to

Step 8

Go to

Step 12

8Measure the voltage between the IAT sensor signal

circuit at the ECM harness connector and ground.

Does the voltage measure near the specified value? 0 V Go to

Step 9

Go to

Step 13

9Measure the voltage between the ECT sensor signal

circuit at the ECM harness connector and ground.

Does the voltage measure near the specified value? 0 V Go to

Step 10

Go to

Step 14

10 Measure the voltage between the TFT sensor signal

circuit at the ECM harness connector and ground.

Does the voltage measure near the specified value? 0 V Go to

Step 15

Go to

Step 16

11 Locate and repair the short to voltage in the BARO

sensor signal circuit.

Is the action complete? — Verify repair —

12 Locate and repair the short to voltage in the TP sensor

signal circuit.

Is the action complete? — Verify repair —

Step NoYesValue(s)Action

13 Locate and repair the short to voltage in the IA T sensor

signal circuit.

Is the action complete? — Verify repair —

14 Locate and repair the short to voltage in the ECT

sensor signal circuit.

Is the action complete? — Verify repair —

15 Locate and repair the short to voltage in the TFT sensor

signal circuit.

Is the action complete? — Verify repair —

16 Replace the ECM.

Is the action complete? —

Go to

OBD

System

Check

—

Tech 2 Data Definitions and Ranges

A/C CLUTCH–Tech 2 Displays ON or OFF–

Indicates whether the ECM has commanded the A/C

clutch ON. Used in A/C system diagnostic.

A/C REQUEST — Tech 2 Displays YES or NO —

Indicates the state of the A/C request input circuit from the

HVAC controls. The ECM uses the A/C request signal to

determine whether A/C compressor operation is being

requested.

AIR/FUEL RATIO — Tech 2 Range 0.0-25.5 —

Air/fuel ratio indicates the ECM commanded value. In

closed loop, the air/fuel ratio should normally be

displayed around “14.2–14.7.” A lower air/fuel ratio

indicates a richer commanded mixture, which may be

seen during power enrichment or TWC protection modes.

A higher air/fuel ratio indicates a leaner commanded

mixture. This can be seen during deceleration fuel mode.

BARO kpa — Tech 2 Range 10-105 kpa/0.00-5.00

Volts —

The barometric pressure reading is determined from the

BARO sensor signal monitored during key up and wide

open throttle (WOT) conditions. The barometric pressure

is used to compensate for altitude differences and is

normally displayed around “61-104” depending on

altitude and barometric pressure.

CHECK TRANS LAMP–AUTO TRANSMISSION–

Indicates the need to check for a DTC with the Tech 2

when the lamp is flashing 0.2 seconds ON and 0.2

seconds OFF.

CMP ACT. COUNTER –Cam Position

ActivityDECEL FUEL MODE—Tech 2 Display

ACTIVE or INACTVE—

“ACTIVE” displayed indicates that the ECM has detected

conditions appropriate to operate in deceleration fuel

mode. The ECM will command the deceleration fuel

mode when it detects a closed throttle position while the

vehicle is traveling over 20 mph. While in the decreasing

fuel mode, the ECM will decrease the amount of fuel

delivered by entering open loop and decreasing the

injector pulse width.

DESIRED IDLE — Tech 2 Range 0-3187 RPM —

The idle speed that the ECM is commanding. The ECM

will compensate for various engine loads based on engine

coolant temperature, to keep the engine at the desired

speed.

ECT — (Engine Coolant Temperature) Tech 2

Range –40°C to 151°C (–40°F to 304°F) —

The engine coolant temperature (ECT) is mounted in the

coolant stream and sends engine temperature

information to the ECM. The ECM applies 5 volts to the

ECT sensor circuit. The sensor is a thermistor which

changes internal resistance as temperature changes.

When the sensor is cold (high resistance), the ECM

monitors a high signal voltage and interprets that as a cold

engine. As the sensor warms (decreasing resistance),

the voltage signal will decrease and the ECM will interpret

the lower voltage as a warm engine.

ENGINE LOAD — Tech 2 Range 0%-100% —

Engine load is calculated by the ECM from engine speed

and MAF sensor readings. Engine load should increase

with an increase in RPM or air flow.

TIME FROM START — Tech 2 Range

00:00:00-99:99:99 Hrs:Min:Sec —

Indicates the time elapsed since the engine was started.

If the engine is stopped, engine run time will be reset to

00:00:00.

ENGINE SPEED — Range 0-9999 RPM —

Engine speed is computed by the ECM from the 58X

reference input. It should remain close to desired idle

under various engine loads with engine idling.

FUEL PUMP — Tech 2 Displays ON or OFF —

Indicates the ECM commanded state of the fuel pump

relay driver circuit.

FUEL TRIM CELL — Tech 2 Range 0-21 —

The fuel trim cell is dependent upon engine speed and

MAF sensor readings. A plot of RPM vs. MAF is divided

into 22 cells. Fuel trim cell indicates which cell is currently

active.

FUEL TRIM LEARN

— Tech 2 Displays NO or YES —

When conditions are appropriate for enabling long term

fuel trim corrections, fuel trim learn will display “YES.”

This indicates that the long term fuel trim is responding to

the short term fuel trim. If the fuel trim learn displays

“NO,” then long term fuel trim will not respond to changes

in short term fuel trim.

HO2S SEN.Tech 2 Range 0-1132 mV–

Represents the fuel control exhaust oxygen sensor

output voltage. Should fluctuate constantly within a range

between 10 mV (lean exhaust) and 1000 mV (rich

exhaust) while operating in closed loop.

HO2S SEN.Tech 2 Displays READY YES/NO–

Indicates the status of the exhaust oxygen sensor. The

Tech 2 will indicate that the exhaust oxygen sensor is

ready when the ECM detects a fluctuating HO2S voltage

sufficient to allow closed loop operation. This will not

occur unless the exhaust oxygen sensor is warmed up.

IAC POSITION — Tech 2 Range 0-255 Counts —

Displays the commanded position of the idle air control

pintle in counts. A larger number of counts means that

more air is being commanded through the idle air

passage. Idle air control should respond fairly quickly to

changes in engine load to maintain desired idle RPM.

IAT (INTAKE AIR TEMPERATURE)— Tech 2 Range

–40°C to 151°C (–40°F to 304°F) —

The ECM converts the resistance of the intake air

temperature sensor to degrees. Intake air temperature

(IA T) is used by the ECM to adjust fuel delivery and spark

timing according to incoming air density.

IGNITION VOLTAGE

— Tech 2 Range 0-25.5 Volts —

This represents the system voltage measured by the

ECM at its ignition feed.

INJ. PULSE BANK 1 – Tech 2 Range 0-1000 msec. –

Indicates the amount of time the ECM is commanding

each injector “ON” during each engine cycle. A longer

injector pulse width will cause more fuel to be delivered.

Injector pulse width should increase with increased

engine load.

LONG TERM FUEL TRIM BANK 1

The long term fuel trim is derived from the short term fuel

trim values and represents a long term correction of fuel

delivery for the bank in question. A value of 0% indicates

that fuel delivery requires no compensation to maintain

the ECM commanded air/fuel ratio. A negative value

significantly below 0% indicates that the fuel system is

rich and fuel delivery is being reduced (decreased injector

pulse width). A positive value significantly greater than

0% indicates that a lean condition exists and the ECM is

compensating by adding fuel (increased injector pulse

width). Because long term fuel trim tends to follow short

term fuel trim, a value in the negative range due to

canister purge at idle should not be considered unusual.

Fuel trim values at maximum authority may indicate an

excessively rich or lean system.

MAF — Tech 2 Range 0.0-512 g/s —

MAF (mass air flow) is the MAF input frequency

converted to grams of air per second. This indicates the

amount of air entering the engine.

MIL — Tech 2 Displays ON or OFF —

Indicates the ECM commanded state of the malfunction

indicator lamp.

POWER ENRICHMENT — Tech 2 Displays ACTIVE

or INACTIVE —

“ACTIVE” displayed indicates that the ECM has detected

conditions appropriate to operate in power enrichment

mode. The ECM will command power enrichment mode

when a large increase in throttle position and load is

detected. While in power enrichment mode, the ECM will

increase the amount of fuel delivered by entering open

loop and increasing the injector pulse width. This is done

to prevent a possible sag or hesitation from occurring

during acceleration.

SPARK — Tech 2 Range –64° to 64° —

Displays the amount of spark advance being commanded

by the ECM on the IC circuit.

START-UP ECT — Tech 2 Range –40°C to 151°C

(–40°F to 304°F) —

Indicates the engine coolant temperature at the time that

the vehicle was started. Used by the HO2S diagnostic to

determine if the last start-up was a cold start.

TP — Tech 2 Range 0%-100% —

TP (throttle position) angle is computed by the ECM from

the TP sensor voltage. TP angle should display “0%” at

idle and “100%” at wide open throttle.

TP SENSOR — Tech 2 Range 0.00-5.00 Volts —

The voltage being monitored by the ECM on the TP

sensor signal circuit.

CATALYST PROTECTION MODE— Tech 2 Displays

YES or NO —

“YES” displayed indicates that the ECM has detected

conditions appropriate to operate in TWC protection

mode. The ECM will decrease the air/fuel ratio to a value

that depends on mass air flow (higher mass air flow =

lower air/fuel ratio).

WEAK CYLINDER –Tech 2 Displays Cylinder

Number—

This indicates that the ECM has detected crankshaft

speed variations that indicate 2% or more cylinder firing

events are misfires.

Typical Scan Data Values

Use the Typical Scan Data Values Table only after the

On-Board Diagnostic System Check has been

completed, no DTC(s) were noted, and you have

determined that the on-board diagnostics are functioning

properly. Tech 2 values from a properly-running engine

may be used for comparison with the engine you are

diagnosing. The typical scan data values represent

values that would be seen on a normally-running engine.

NOTE:A Tech 2 that displays faulty data should not be

used, and the problem should be reported to the Tech 2

manufacturer. Use of a faulty Tech 2 can result in

misdiagnosis and unnecessary replacement of parts.

Only the parameters listed below are referred to in this

service manual for use in diagnosis. For further

information on using the Tech 2 to diagnose the ECM and

related sensors, refer to the applicable reference section

listed below. If all values are within the typical range

described below, refer to the

Symptoms

section for

diagnosis.

Test Conditions

Engine running, lower radiator hose hot, transmission in

park or neutral, closed loop, accessaries off, brake not

applied and air conditioning off.

3.2L V-6 Engine (Automatic and Manual Transmission)

Tech 2

Parameter Data List Units

Displayed Typical Data

Values (IDLE) Typical Data

Values

(2500 RPM)

Refer To

A/C Clutch Engine On/Off Off Off General Description and

Operation, A/C Clutch

Circuit Operation

A/C Request Engine On/Off Off Off General Description and

Operation, A/C Request

Signal

Air/Fuel Ratio Engine Ratio: _ to

114.7 14.7 General Description and

Operation, Fuel System

Metering Purpose

Barometric

Pressure Engine kpa Depend

barometric

pressure

Depend

barometric

pressure

—

Catalyst

Protection Mode Engine Yes/No — — —

Check Trans

Lamp (Auto

Trans)

Engine On/Off Off Off Automatic Transmission

Diagnosis

CMP Act.

Counter (Cam

Position Activity)

Engine Counts 0-255, always

increasing 0-255, always

increasing DTC P0341 and P0342

Deceleration

Fuel Mode Engine On/Off Off Off General Description and

Operation, Deceleration

Mode

Desired Idle Engine RPM 760 2500 General Description and

Operation, Idle Air Control

(IAC) Valve

ECT (Engine

Coolant Temp) Engine Degrees C,

Degrees F 80-100°C

(176-212°F) 80-100°C

(176-212°F) General Description and

Operation, Engine Coolant

Temperature (ECT)

Sensor

Engine Load Engine Percent 2.0% - 5.5% 9.0% - 20.0% General Description and

Operation, Mass Air Flow

(MAF) Sensor

Time From Start Engine Sec Varies. Resets

at each engine

start.

Varies. Resets

at each engine

start. —

Engine Speed Engine RPM Within –50 to

+100 of

“Desired Idle”

Actual engine

speed DTCs: P1508, P1509

Fuel Pump Engine On/Off On On Engine Fuel

Fuel Trim Cell Engine Cell

number 49, 50, 51 21, 22, 23 Diagnosis, Fuel Trim Cell

Diagnostic Weights

Fuel Trim

Leaned Engine Yes/No No Yes Diagnosis, Fuel Trim

Monitor

HO2S Sen.

(millivolts) Engine Millivolts 50-950

changing slowly 50-950

changing slowly General Description and

Operation

HO2S

(ready/not

ready)

Engine Ready

Yes/No Ready

Yes Ready

Yes General Description and

Operation, Fuel Control

HO2S; DTC: P0135

IAC Position Engine Steps 5-50 10-70 —

Tech 2

Parameter Data List Units

Displayed Typical Data

Values (IDLE) Typical Data

Values

(2500 RPM)

Refer To

IAT (Intake Air

Temp) Engine Degrees C,

Degrees F 0-100°C,

depends on

underhood

0-80°C,

depends on

underhood

General Description and

Operation, Intake Air

Temperature (IAT) Sensor

Ignition Voltage Engine Volts 12.8-14.5 12.8-14.5 General Description and

Operation, Electronic

Ignition System

Inj. Pulse Bank

1Engine Millisecond

s2.0-4.0 2.5-4.5 General Description, Fuel

Metering, Fuel Injector

Long Term FT

Bank 1 (Long

Term Fuel Trim)

Engine Counts

and

Percent

counts, –12% to

+17% counts, –10% to

+15% Diagnosis, Fuel Trim

System Monitor; DTCs:

P0171, P0172

MAF (Mass Air

Flow) Engine Grams per

second 2.85-6.65 9.5-16.5 General Description and

Operation, MAF; DTCs:

P101, P0102, P0103

MIL

(Malfunction

Indicator Light)

Engine On/Off Off Off On-Board Diagnostic

System Check

EVAP Purge

Solenoid Engine % — — —

PSP Switch

(Power Steering

Pressure)

Engine Normal/Hig

h Pressure Normal Normal Power Steering Gear and

Pump, General

Description, pressure

Switch

Power

Enrichment Engine Yes/No No No General Description and

Operation, Acceleration

Mode

B1S1 (Short

Term) Engine Rich/Lean Always

changing Always

changing General Description and

Operation, Fuel Control

HO2S

Shrt Term FT

Bank 1 (Short

Term Fuel Trim)

Engine Counts

and

Percent

112 to 154

counts, –12% to

+20%

112 to 154

counts, –12% to

+20%

Diagnosis, Fuel Trim

System Monitor; DTCs:

P0171, P0172

Spark

(Advance) Engine Degrees

Before Top

Dead

Center

10-15°CA 34-44°CA General Description and

Operation, Electronic

Ignition System

Start-Up ECT

(Engine Coolant

Temp)

Engine Degrees C,

Degrees F Depends on

engine coolant

temperature at

time of start-up

Depends on

engine coolant

temperature at

time of start-up

General Description and

Operation, Engine Coolant

Temperature (ECT)

Sensor

TCC Engaged

(Torque

Converter

Clutch)

Engine No/Yes No No T ransmission Diagnosis

Torque

Management Engine Inactive/Ac

tive Inactive Inactive Transmission Diagnosis

TP (Throttle

Position) Engine Percent 0 5-10 General Description and

Operation, Throttle

Position (TP) Sensor;

DTCs: P0121,

P0122,P0123

Tech 2

Parameter Data List Units

Displayed Typical Data

Values (IDLE) Typical Data

Values

(2500 RPM)

Refer To

TP Sensor

(Throttle

Position)

Engine Volts 0.4-0.7 0.60-1.00 General Description and

Operation, Throttle

Position (TP) Sensor;

DTCs: P0121,

P0122,P0123

Vehicle Speed Engine MPH /

km/h 00Transmission Diagnosis

Fuel System

Status Engine Open /

Close loop Close loop Close loop General Description

No Malfunction Indicator Lamp (MIL)

060RW045

Circuit Description

The “Check Engine” lamp (MIL) should always be

illuminated and steady with the ignition “ON” and the

engine stopped. Ignition feed voltage is supplied to the

MIL bulb through the meter fuse. The Engine Control

Module ECM turns the MIL “ON” by grounding the MIL

driver circuit.

Diagnostic Aids

An intermittent MIL may be cased by a poor connection,

rubbed-through wire insulation, or a wire broken inside

the insulation. Check for the following items:

DInspect the ECM harness and connections for

improper mating, broken locks, improperly formed or

damaged terminals, poor terminal-to-wire connection,

and damaged harness.

DIf the engine runs OK, check for a faulty light bulb, an

open in the MIL driver circuit, or an open in the

instrument cluster ignition feed.

DIf the engine cranks but will not run, check for an open

ECM ignition or battery feed, or a poor ECM to engine

ground.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. A “No MIL” condition accompanied by a no-start

condition suggests a faulty ECM ignition feed or

battery feed circuit.

9. Using a test light connected to B+, probe each of the

ECM ground terminals to ensure that a good ground

is present. Refer to

ECM Terminal End View

for

terminal locations of the ECM ground circuits.

12.In this step, temporarily substitute a known good

relay for the ECM relay. The horn relay is nearby,

and it can be verified as “good” simply by honking

the horn. Replace the horn relay after completing

this step.

No Malfunction Indicator Lamp (MIL)

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Attempt to start the engine.

Does the engine start? —Go to

Step 3

Go to

Step 6

3Check the meter fuse for the instrument cluster ignition

feed circuit.

Is the fuse OK? —Go to

Step 4

Go to

Step 16

4Ignition “ON,” probe the ignition feed circuit at the

cluster connector with a test light to ground.

Is the test light “ON?” —Go to

Step 5

Go to

Step 13

51. Ignition “OFF.”

2. Disconnect the ECM.

3. Jumper the MIL driver circuit at the ECM connector

to ground.

4. Ignition “ON.”

Is the MIL “ON?” —Go to

Step 10

Go to

Step 11

6Check the ECM ignition feed and battery feed fuses (15

A engine fuse and 15 A ECM fuse).

Are both fuses OK? —Go to

Step 7

Go to

Step 15

71. Ignition “OFF.”

2. Disconnect the ECM.

3. Ignition “ON.”

4. Probe the ignition feed circuit at the ECM harness

connector with a test light to ground.

Is the test light “ON?” —Go to

Step 8

Go to

Step 12

8Probe the battery feed circuit at the ECM harness

connector with a test light to ground.

Is the test light “ON?” —Go to

Step 9

Go to

Step 14

9Check for a faulty ECM ground connection.

Was a problem found? — Verify repair Go to

Step 10

10 Check for damaged terminals at the ECM.

Was a problem found? — Verify repair Go to

Step 17

11 Check for an open MIL driver circuit between the ECM

and the MIL.

Was a problem found? — Verify repair Go to

Step 18

12 Substitute a known “good” relay for the ECM main

relay.

Was the malfunction fixed? — Verify repair Go to

Step 13

13 Repair the open in the ignition feed circuit.

Is the action complete? — Verify repair —

14 Locate and repair the open ECM battery feed circuit.

Is the action complete? — Verify repair —

Step NoYesValue(s)Action

15 Locate and repair the short to ground in the ECM

ignition feed circuit or ECM battery feed circuit.

Is the action complete? — Verify repair —

16 Locate and repair the short to ground in the ignition

feed circuit to the instrument cluster, and replace the

fuse.

Is the action complete? — Verify repair —

17 Replace the ECM.

Is the action complete? — Verify repair —

18 Check the MIL driver circuit for a poor connection at the

instrument panel connector.

Was a problem found? — Verify repair

Go to

Instrument

Panel

Electrical

Diagnosis

Malfunction Indicator Lamp (MIL) “ON” Steady

060RW045

Circuit description

The “Check Engine” lamp (MIL) should always be

illuminated and steady with ignition “ON” and the engine

stopped. Ignition feed voltage is supplied directly to the

MIL indicator . The Engine Control Module ECM turns the

MIL “ON” by grounding the MIl driver circuit.

The MIL should not remain “ON” with the engine running

and no DTC(s) set. A steady MIl with the engine running

and no DTC(s) suggests a short to ground in the MIl driver

circuit.

Diagnostic Aids

An intermittent may be caused by a poor connection,

rubbed–through wire insulation, or a wire broken inside

the insulation. Check for the following items:

DPoor connection or damaged harness – Inspect the

ECM harness and connectors for improper mating,

broken locks, improperly formed or damaged

terminals, poor terminal-to-wire connection, and

damaged harness.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. If the MIL does not remain “ON” when the ECM is

disconnected, the MIL driver wiring is not faulty.

3. If the MIL driver circuit is OK, the instrument panel

cluster is faulty.

6. This vehicle is equipped with a ECM which utilizes

an electrically erasable programmable read only

memory (EEPROM).

Malfunction Indicator Lamp (MIL) “ON” Steady

Step Action Value(s) YesNo

1Was the “On-Board diagnostic (OBD) System Check”

performed? — Go to

Step 2

Go to

OBD

System

Check

21. Ignition “OFF,” disconnect ECM.

2. Ignition “ON,” observe the MIL (Service Engine

Soon lamp).

Is the MIL “ON?” —Go to

Step 3

Go to

Step 5

31. Ignition “OFF,” disconnect the instrument panel

cluster.

2. Check the MIL driver circuit between the ECM and

the instrument panel cluster for a short to ground.

3. If a problem is found, repair as necessary.

Was the MIL driver circuit shorted to ground? —

Go to

OBD

System

Check

Go to

Step 4

4Replace the instrument panel cluster.

Is the action complete? —

Go to

OBD

System

Check

—

51. Ignition “OFF,” reconnect the ECM.

2. Ignition “ON,” reprogram the ECM. Refer to

On-Vehicle Service

Engine Control Module and

Sensor

for procedures.

3. Using the Tech 2 output controls function, select

MIL dash lamp control and command the MIL

“OFF.”

Did the MIL turn “OFF?” —

Go to

OBD

System

Check

Go to

Step 6

6Replace the ECM.

Is the action complete? —

Go to

OBD

System

Check

—

060RW051

Engine Cranks But Will Not Run

Circuit Description

The electronic Ignition system uses a coil-at-plug method

of spark distribution. In this type of ignition system, the

Engine Control Module ECM triggers the correct driver

inside the ignition coil, which then triggers the correct

ignition coil based on the 58X signal received from the

crankshaft position sensor (CKP). The spark plug

connected to the coil fires when the ignition coil opens the

ground circuit for the coil’s primary circuit.

During crank, the ECM monitors the CKP 58X signal. The

CKP signal is used to determine which cylinder will fire

first. After the CKP 58X signal has been processed by the

ECM, it will command all six injectors to allow a priming

shot of fuel for all the cylinders. After the priming, the

injectors are left “OFF” during the next six 58X reference

pulses from the CKP. This allows each cylinder a chance

to use the fuel from the priming shot. During this waiting

period, a camshaft position (CMP) signal pulse will have

been received by the ECM. The CMP signal allows the

ECM to operate the injectors sequentially based on

camshaft position. If the camshaft position signal is not

present at start-up, the ECM will begin sequential fuel

delivery with a 1-in-6 chance that fuel delivery is correct.

The engine will run without a CMP signal, but will set a

DTC code.

Diagnostic Aids

An intermittent problem may be caused by a poor

connection, rubbed-through wire insulation or a wire

broken inside the insulation. Check for the following

items:

DPoor connection or damaged harness – Inspect the

ECM harness and connectors for improper mating,

broken locks, improperly formed or damaged

terminals, poor terminal-to-wore connection, and

damaged harness.

DFaulty engine coolant temperature sensor – Using a

Tech 2, compare engine coolant temperature with

intake air temperature on a completely cool engine.

Engine coolant temperature should be within 10°C of

intake air temperature. If not, replace the ECT sensor.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

5. An obvious cause of low fuel pressure would be an

empty fuel tank.

6. The engine will easily start and run if a few injectors

are disabled. It is not necessary to test all injectors

at this time since this step is only a test to verify that

all of the injectors have not been disabled by fuel

contamination.

7. A blinking test light verifies that the ECM is

monitoring the crankshaft reference signal and is

capable of activating the injectors. If there is an

open or shorted driver circuit, DTCs 201–206 should

be set.

19.By using a spark tester, each ignition coil’s ability to

produce 25,000 volts is verified.

25.If there is an open or shorted driver circuit, DTCs

201-206 should be set. All six injector driver circuits

can be checked at one time without removing the

intake manifold if a 5–8840–2639–0 test light is

available. This is the alternative procedure:

DWith the ignition “OFF,” disconnect the gray

connector located at the rear of the air filter, attached

to a bracket on the purge canister.

DConnect test light 5–8840–2639–0 to the connector.

Do any of the light constantly illuminate or fail to blink

when the engine is cranked? If so, repair the short or

open circuit, or replace the ECM if indicated.

This procedure only tests the driver circuit as far as the

test connection, so step 31 is added to test the circuit all

the way to the injector.

Engine Cranks But Will Not Run

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Check the 15 A ignition coil fuse, the 15 A engine

device fuse, and the 15A ECM fuse.

Was a fuse blown? —Go to

Step 3

Go to

Step 4

3Check for a short to ground and replace the fuse.

Is the action complete? — Verify repair —

Step NoYesValue(s)Action

41. Ignition “OFF,” install a fuel pressure gauge at the

test fitting on the fuel supply line in the engine

compartment. (Use a shop cloth to absorb any fuel

leakage while making the connection.)

2. Ignition “ON,” observe the fuel pressure.

Is the fuel pressure within the specified values, and

does it hold steady? 285-375 kpa

(43-55 psi) Go to

Step 6

Go to

Step 5

5Is any fuel pressure indicated?

—

Go to

Fuel

System

Electrical Test

Go to

Fuel

System

Diagnosis

6Install the switch box 5–8840–2618–0 at the injector

test connector and activate an injector.

Did the fuel pressure drop when the injector was

activated? — Go to

Step 7

Go to

Step 18

7Install an injector test light at the #2 cylinder injector

harness connector.

Does the light blink when the engine is cranked? —Go to

Step 8

Go to

Step 24

81. Ignition “OFF.”

2. Disconnect the 6-pin connector at the ignition coil.

3. With a test light to B+, probe each of the 6 exposed

ignition module pins, one at a time, while the engine

is cranked. (Use the gray narrow METRA–PAK

flexible female connector from the 5-8840-0385-0

kit to make the pin accessible.)

Does the light flash at each pin when the engine is

cranked? — Go to

Step 12

Go to

Step 9

91. Remove the 5-pin connector at the ignition coil.

2. Ignition “ON.”

3. Use a test light at the harness connector to verify

that the module is being supplied with B+ and

ground.

Was a problem found? —Go to

Step 10

Go to

Step 11

10 Repair the open ignition feed circuit or ground circuit to

the ignition coil.

Is the action complete? — Verify repair —

11 Repair the ignition module.

Is the action complete? — Verify repair —

12 1. Reconnect the ignition coil connector.

2. Remove the electrical connector from each coil.

3. With a test light to B+, probe each of the coil

connectors at the wire which runs to the ignition

module. (Wire color will match the wire color at the

ignition module 6-pin connector – green, or green

with a tracer.)

Does the light flash at each coil connector when the

engine is cranked? —Go to

Step 14

Go to

Step 13

13 Check for an open circuit between the ignition coil.

Is the action complete? — Verify repair —

Step NoYesValue(s)Action

14 1. Ignition “ON.”

2. While the coil connectors are disconnected, touch

each coil connector’s ignition feed terminal with a

grounded test light (the ignition feed wire is black

with orange tracer).

Did the test light illuminate? —Go to

Step 16

Go to

Step 15

15 Repair the open ignition feed circuit.

Is the action complete? — Verify repair —

16 While the coil connectors are disconnected, touch

each connector’s secondary ground terminal with a

test light to B+. (The ground wires are black.)

Did the test light illuminate at each coil connector? —Go to

Step 18

Go to

Step 17

17 Repair the open secondary ground circuit.

Is the action complete? — Verify repair —

18 1. Test the fuel for contamination.

2. If a problem is found, clean the fuel system and

correct the contaminated fuel condition as

necessary. Replace the fuel filter and replace any

injectors that are not delivering fuel (see Injector

Balance Test).

Was a problem found? — Verify repair Go to

Step 19

19 1. Remove any ignition coil and install a spark tester at

the spark plug end of the coil.

2. Observe the tester while the engine is cranking.

Was a crisp, blue spark observed? Only one or two

sparks followed by no result is considered the same as

“No Spark.” —Go to

Step 21

Go to

Step 20

20 Replace the ignition coil, and return to Step 19 to test

the remaining coils.

Is the action complete? — Verify repair —

21 Repeat Step 19 for each coil. Remove only one coil at a

time, and reinstall each coil on its spark plug after

testing, but do not refasten coils with screws at this

time.

After all coils have passed the spark test, does the

engine start? —

Refasten all

coils with

their screws Go to

Step 22

22 1. Remove the spark plugs from all cylinders.

2. Visually inspect the spark plug electrodes.

3. Replace any spark plugs with loose or missing

electrodes or cracked insulators.

Did your inspection reveal any spark plugs exhibiting

excessive fouling? —

Correct the

fouling

condition Go to

Step 23

Step NoYesValue(s)Action

23 Refer to

Engine Mechanical Diagnosis

to diagnose the

following conditions:

DFaulty or incorrect camshaft drive belts

DLeaking or sticky valves or rings

DExcessive valve deposits

DLoose or worn rocker arms

DWeak valve springs

DIncorrect valve timing

DLeaking head gasket

Is the action complete? — Verify repair Go to

Step 25

24 Observe the “Engine Speed” data display on the T ech 2

while cranking the engine.

Is the engine RPM indicated? (If the Tech 2 is normally

powered from the cigarette lighter socket, and if the

Tech 2 display goes blank while cranking the engine, it

will be necessary to power the Tech 2 directly from the

vehicle battery.) —Go to

Step 25

Go to

Step 34

25 1. Disconnect the 7-pin gray connector at the rear of

the air filter beneath the point where the air duct

attaches to the MAF sensor.

2. Ignition “ON.”

3. Using a test light connected to ground, probe the

ignition terminal at the ECM (female) side of the

7-pin connector.

Is the test light “ON?” —Go to

Step 26

Go to

Step 32

26 1. At the ECM (female) side of the connector

mentioned in step 25, connect a test light between

the ignition + terminal and one of the injector driver

circuits at the same connector.

2. Ignition “ON.”

3. Observe the test light, and repeat the test for each

injector driver circuit.

Did the test light stay on when checking any of the 6

injector driver circuits? —Go to

Step 27

Go to

Step 29

27 1. Ignition “OFF,” disconnect the ECM.

2. Ignition “ON,” observe the test light.

Is the test light “ON?” —Go to

Step 28

Go to

Step 33

28 Locate and repair the short to ground in the injector

driver circuit.

Is the action complete? — Verify repair —

29 1. Using the same test location as in step 26, connect

a test light between the ignition terminal and one of

the driver circuits.

2. Crank the engine and observe the test light.

3. Repeat for each injector driver circuit.

Did the light blink during the test for each circuit? —Go to

Step 31

Go to

Step 30

30 Check for an open injector driver circuit.

Was a problem found? — Verify repair Go to

Step 33

Step NoYesValue(s)Action

31 1. At the injector (male) side of the gray connector

mentioned in step 25, connect an ohmmeter

between the ignition pin and one of the driver circuit

pins.

2. Check for continuity in the circuit.

3. Repeat for each injector circuit. The readings

should be approximately equal to the specified

value for injector resistance.

Was a problem found? 12.5 ohms Verify repair Go to

Step 8

32 Repair the ignition feed circuit.

Is the action complete? — Verify repair —

33 Replace the ECM.

Is the action complete? — Verify repair —

34 1. Raise the vehicle and disconnect the CKP sensor

harness.

2. Ignition “ON.”

3. With a test light to ground, probe the harness

ignition feed terminal.

Did the light illuminate? —Go to

Step 36

Go to

Step 35

35 Check the ignition feed wire between the sensor and

the ECM for a short to ground or open circuit.

Is the action complete? — Verify repair —

36 1. Ignition “ON.”

2. At the CKP harness connector, connect a test light

between the ignition and ground terminals.

Did the light illuminate? —Go to

Step 38

Go to

Step 37

37 Check the sensor ground circuit for an open or short to

voltage.

Is the action complete? — Verify repair —

38 Check the signal circuit between the sensor and the

ECM for a short to ground, short to voltage, or an open.

Was a problem found? — Verify repair Go to

Step 39

39 Replace the CKP position sensor.

Is the action complete? — Verify repair Go to

Step 33

Fuel System Electrical Test

060RW058

Circuit Description

When the ignition switch is first turned “ON,” the Engine

Control Module ECM energizes the fuel pump relay which

applies power to the in-tank fuel pump. The fuel pump

relay will remain “ON” as long as the engine is running or

cranking and the ECM is receiving 58X crankshaft

position pulses. If no 58X crankshaft position pulses are

present, the ECM de-energizes the fuel pump relay within

2 seconds after the ignition is turned “ON” or the engine is

stopped.

The fuel pump delivers fuel to the fuel rail and injectors,

then to the fuel pressure regulator. The fuel pressure

regulator controls fuel pressure by allowing excess fuel to

be returned to the fuel tank. With the engine stopped and

ignition “ON,” the fuel pump can be turned “ON” by using a

command by the Tech 2.

Diagnostic Aids

An intermittent may be caused by a poor connection,

rubbed-through wire insulation, or a wire broken inside

the insulation. Check for the following items:

DPoor connection or damaged harness – Inspect the

ECM harness and connectors for improper mating,

broken locks, improperly formed or damaged

terminals, poor terminal-to-wire connection, and

damaged harness.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. If the fuel pump is operating but incorrect pressure is

noted, the fuel pump wiring is OK and the “Fuel

System Pressure Test” chart should be used for

diagnosis.

CAUTION:To reduce the risk of fire and personal

injury:

DIt is necessary to relieve fuel system pressure

before connecting a fuel pressure gauge. Refer to

Fuel Pressure Relief Procedure, below.

DA small amount of fuel may be released when

disconnecting the fuel lines. Cover fuel line

fittings with a shop towel before disconnecting, to

catch any fuel that may leak out. Place the towel in

an approved container when the disconnect is

completed.

Fuel Pressure Relief Procedure

1.Remove the fuel cap.

2.Remove the fuel pump relay from the underhood

relay center.

3.Start the engine and allow it to stall.

4.Crank the engine for an additional 3 seconds.

Fuel Gauge Installation

1.Remove the shoulder fitting cap.

2.Install fuel gauge 5-8840-0378-0 to the fuel feed line

located in front of and above the right side valve

cover.

3.Reinstall the fuel pump relay.

Fuel System Electrical Test

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Read the “Caution” above.

2. Relieve the fuel system pressure and install the fuel

pump pressure gauge to the test fitting.

3. Use a Tech 2 to command the fuel pump “ON.”

Is there an immediate pressure build-up which

indicates the pump is running? —Go to

Step 3

Go to

Step 4

31. V erify that the pump is not running by removing the

fuel filler cap and listening.

2. Command the pump “ON” with the Tech 2.

Did the pump turn “OFF” after 2 seconds? —Test

completed Go to

Step 12

41. Ignition “OFF.”

2. Remove the fuel pump relay.

3. Using a test light connected to ground, probe the

battery feed to the relay.

Did the light illuminate? —Go to

Step 6

Go to

Step 5

5Repair short or open battery feed to fuel pump relay.

Is the action complete? — Verify repair —

61. Connect a test light between the two wires that

connect to the fuel pump relay pull-in coil.

2. Ignition “ON.”

Did the test light illuminate for 2 seconds and then turn

off? — Go to

Step 12

Go to

Step 7

71. With a test light connected to battery (–), probe the

fuel pump relay connector at the wire which runs

from the relay pull–in coil to the ECM.

2. Ignition “ON.”

Did the test light illuminate for 2 seconds and then turn

off? — Go to

Step 8

Go to

Step 9

8Locate and repair open in the fuel pump relay ground

circuit.

Is the action complete? — Verify repair —

Step NoYesValue(s)Action

9Check for short or open between the ECM and the fuel

pump relay.

Was a problem found? — Verify repair Go to

Step 10

10 1. Check the fuel pump relay circuit for a poor terminal

connection at the ECM.

2. If a problem is found, replace terminal as necessary.

Was a problem found? — Verify repair Go to

Step 11

11 Replace the ECM.

Is the action complete? — Verify repair —

12 1. Reconnect the fuel pump relay.

2. Disconnect the fuel pump electrical connector at the

fuel tank.

3. Using a test light connected to ground, probe the

fuel pump feed wire (harness side).

4. Command the fuel pump “ON” with a Tech 2.

Did the light illuminate for 2 seconds? —Go to

Step 15

Go to

Step 13

13 1. Substitute a known good realy for the fuel pump

realy.

2. Leave the test light connected as in step 12.

3. Command the fuel pump “ON” with the Tech 2.

4. After this test, re-connect the known good relay in

its proper location.

Did the test light illuminate for 2 seconds when the fuel

pump was commanded “ON?” —Go to

Step 17

Go to

Step 14

14 Check for a short circuit, blown fuse or open circuit

between the relay and the fuel tank.

Is the action complete? — Verify repair —

15 1. With the fuel pump electrical connector at the fuel

tank disconnected, connect a test light between the

feed wire and the ground wire (harness side).

2. Command the fuel pump “ON” with a Tech 2.

Did the test light illuminate for 2 seconds? —Go to

Step 18

Go to

Step 16

16 Repair the open circuit in the fuel pump ground wire.

Is the action complete? — Verify repair —

17 Replace the fuel pump relay.

Is the action complete? — Verify repair —

18 Replace the fuel pump.

Is the action complete? — Verify repair —

Fuel System Diagnosis

060RW245

Legend

(1) Fuel Filler Cap

(2) Fuel Tank

(3) Rollover Valve

(4) Fuel Pump Assembly

(5) Fuel Filter

(6) Fuel Rail Right

(7) Intake Air Port Right Bank

(8) Fuel Rail Left

(9) Intake Air Port Left Bank

(10) Fuel Pressure Control Valve

(11) Common Chamber

(12) Duty Solenoid Valve

(13) Throttle Valve

(14) Canister

(15) Fuel Gauge

(16) Check Valve

Circuit Description

When the ignition switch is turned “ON,” the Engine

Control Module ECM will turn “ON” the in-tank fuel pump.

The in-tank fuel pump will remain “ON” as long as the

engine is cranking or running and the ECM is receiving

58X crankshaft position pulses. If there are no 58X

crankshaft position pulses, the ECM will turn the in-tank

fuel pump “OFF” 2 seconds after the ignition switch is

turned “ON” or 2 seconds after the engine stops running.

The in-tank fuel pump is an electric pump within an

integral reservoir. The in-tank fuel pump supplies fuel

through an in-line fuel filter to the fuel rail assembly. The

fuel pump is designed to provide fuel at a pressure above

the pressure needed by the fuel injectors. A fuel pressure

regulator, attached to the fuel rail, keeps the fuel available

to the fuel injectors at a regulated pressure. Unused fuel

is returned to the fuel tank by a separate fuel return line.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. Connect the fuel pressure gauge to the fuel feed line

as shown in the fuel system illustration. Wrap a

shop towel around the fuel pressure connection in

order to absorb any fuel leakage that may occur

when installing the fuel pressure gauge. With the

ignition switch “ON” and the fuel pump running, the

fuel pressure indicated by the fuel pressure gauge

should be 333-376 kpa (3.4-3.8 kg/cm2 / 48-55 psi).

This pressure is controlled by the amount of

pressure the spring inside the fuel pressure

regulator can provide.

3. A fuel system that cannot maintain a constant fuel

pressure has a leak in one or more of the following

areas:

DThe fuel pump check valve.

DThe fuel pump flex line.

DThe valve or valve seat within the fuel pressure

regulator.

DThe fuel injector(s).

4. Fuel pressure that drops off during acceleration,

cruise, or hard cornering may case a lean condition.

A lean condition can cause a loss of power, surging,

or misfire. A lean condition can be diagnosed using

a Tech 1 Tech 2. If an extremely lean condition

occurs, the oxygen sensor(s) will stop toggling. The

oxygen sensor output voltage(s) will drop below 500

mV. Also, the fuel injector pulse width will increase.

IMPORTANT:Make sure the fuel system is not

operating in the “Fuel Cut-Off Mode.”

When the engine is at idle, the manifold pressure is

low (high vacuum). This low pressure (high vacuum)

is applied to the fuel pressure regulator diaphragm.

The low pressure (high vacuum) will offset the

pressure being applied to the fuel pressure regulator

diaphragm by the spring inside the fuel pressure

regulator. When this happens, the result is lower fuel

pressure. The fuel pressure at idle will vary slightly as

the barometric pressure changes, but the fuel

pressure at idle should always be less than the fuel

pressure noted in step 2 with the engine “OFF.”

16.Check the spark plug associated with a particular

fuel injector for fouling or saturation in order to

determine if that particular fuel injector is leaking. If

checking the spark plug associated with a particular

fuel injector for fouling or saturation does not

determine that a particular fuel injector is leaking,

use the following procedure:

DRemove the fuel rail, but leave the fuel lines and

injectors connected to the fuel rail. Refer to

Fuel Rail

Assembly

On-Vehicle Service

DLift the fuel rail just enough to leave the fuel injector

nozzles in the fuel injector ports.

CAUTION:In order to reduce the risk of fire and

personal injury that may result from fuel spraying on

the engine, verify that the fuel rail is positioned over

the fuel injector ports and verify that the fuel injector

retaining clips are intact.

DPressurize the fuel system by connecting a 10 amp

fused jumper between B+ and the fuel pump relay

connector.

DVisually and physically inspect the fuel injector

nozzles for leaks.

17.A rich condition may result from the fuel pressure

being above 376 kpa (55 psi). A rich condition may

cause a DTC P0132 or a DTC P0172 to set.

Driveability conditions associated with rich

conditions can include hard starting (followed by

black smoke) and a strong sulfur smell in the

exhaust.

20.This test determines if the high fuel pressure is due

to a restricted fuel return line or if the high fuel

pressure is due to a faulty fuel pressure regulator.

21.A lean condition may result from fuel pressure

below 333 kpa (48 psi). A lean condition may cause

a DTC P0131 or a DTC P0171 to set. Driveability

conditions associated with lean conditions can

include hard starting (when the engine is cold ),

hesitation, poor driveability, lack of power, surging ,

and misfiring.

22.Restricting the fuel return line causes the fuel

pressure to rise above the regulated fuel pressure.

Command the fuel pump “ON” with the Tech 2. The

fuel pressure should rise above 376 kpa (55 psi) as

the fuel return line becomes partially closed.

NOTE:Do not allow the fuel pressure to exceed 414 kpa

(60 psi). Fuel pressure in excess of 414 kpa (60 psi) may

damage the fuel pressure regulator.

CAUTION:To reduce the risk of fire and personal

injury:

DIt is necessary to relieve fuel system pressure

before connecting a fuel pressure gauge. Refer to

Fuel Pressure Relief Procedure, below.

DA small amount of fuel may be released when

disconnecting the fuel lines. Cover fuel line

fittings with a shop towel before disconnecting, to

catch any fuel that may leak out. Place the towel in

an approved container when the disconnect is

completed.

Fuel Pressure Relief Procedure

1. Remove the fuel cap.

2. Remove the fuel pump relay from the underhood

relay center.

3. Start the engine and allow it to stall.

4. Crank the engine for an additional 3 seconds.

Fuel Gauge Installation

1. Remove the shoulder fitting cap.

2. Install fuel gauge 5-8840-0378-0 to the fuel supply

line located in front of and above the right side valve

cover.

3. Reinstall the fuel pump relay.

Fuel System Diagnosis

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Turn the ignition “OFF.”

2. Turn the air conditioning system “OFF.”

3. Relieve fuel system pressure and install the fuel

pressure gauge.

4. Turn the ignition “ON.”

NOTE: The fuel pump will run for approximately 2

seconds. Use the Tech 2 to command the fuel pump

“ON”.

5. Observe the fuel pressure indicated by the fuel

pressure gauge with the fuel pump running.

Is the fuel pressure within the specified limits? 290-376 kpa

(42-55 psi) Go to

Step 3

Go to

Step 17

3NOTE: The fuel pressure will drop when the fuel pump

stops running, then it should stabilize and remain

constant.

Does the fuel pressure indicated by the fuel pressure

gauge remain constant? —Go to

Step 4

Go to

Step 12

41. When the vehicle is at normal operation

temperature, turn the ignition “ON” to build fuel

pressure and observe the measurement on the

gauge.

2. Start the engine and observe the fuel pressure

gauge.

Did the reading drop by the amount specified after the

engine was started? 21-105 kpa

(3-15 psi) Go to

Step 5

Go to

Step 9

5Is fuel pressure dropping off during acceleration,

cruise, or hard cornering? —Go to

Step 6

Check for

improper fuel

6Visually and physically inspect the following items for a

restriction:

DThe in-pipe fuel filter.

DThe fuel feed line.

Was a restriction found? — Verify repair Go to

Step 7

7Remove the fuel tank and visually and physically

inspect the following items:

DThe fuel pump strainer for a restriction.

DThe fuel line for a leak.

DVerify that the correct fuel pump is in the vehicle.

Was a problem found in any of these areas? — Verify repair Go to

Step 8

8Replace the fuel pump.

Is the action complete? — Verify repair —

91. Disconnect the vacuum hose from the fuel pressure

regulator.

2. With the engine idling, apply 12-14 inches of

vacuum to the fuel pressure regulator.

Does the fuel pressure indicated by the fuel pressure

gauge drop by the amount specified? 21-105 kpa

(3-15 psi) Go to

Step 10

Go to

Step 11

Step NoYesValue(s)Action

10 Locate and repair the loss of vacuum to the fuel

pressure regulator.

Is the action complete? — Verify repair —

11 Replace the fuel pressure regulator.

Is the action complete? — Verify repair —

12 1. Run the fuel pump with the Tech 2.

2. After pressure has built up, turn off the pump and

clamp the supply hose shut with suitable locking

pliers.

Does the fuel pressure indicated by the fuel pressure

gauge remain constant? —Go to

Step 13

Go to

Step 15

13 Visually inspect the fuel supply line and repair any

leaks.

Was a problem found? — Verify repair Go to

Step 14

14 Remove the fuel tank and inspect for leaky hose or

in-tank fuel line.

Was a problem found? — Verify repair Go to

Step 8

15 1. If the pliers are still clamped to the fuel supply hose,

remove the locking pliers.

2. With suitable locking pliers, clamp the fuel return

line to prevent fuel from returning to the fuel tank.

3. Run the fuel pump with the Tech 2.

4. After pressure has built up, remove power to the

pump.

Does the fuel pressure indicated by the fuel pressure

gauge remain constant? —Go to

Step 11

Go to

Step 16

16 Locate and replace any leaking fuel injector(s).

Is the action complete? — Verify repair —

17 Is the fuel pressure indicated by the fuel pressure

gauge above the specified limit? 376 kpa (55

psi) Go to

Step 18

Go to

Step 21

18 1. Relieve the fuel pressure. Refer to the

Fuel

Pressure Relief.

2. Disconnect the fuel return line from the fuel rail.

3. Attach a length of flexible hose to the fuel rail return

outlet passage.

4. Place the open end of the flexible hose into an

approved gasoline container.

5. Run the fuel pump with the Tech 2.

6. Observe the fuel pressure indicated by the fuel

pressure gauge with the fuel pump running.

Is the fuel pressure within the specified limits? 290-376 kpa

(42-55 psi) Go to

Step 19

Go to

Step 20

19 Locate and correct the restriction in the fuel return line.

Is the action complete? — Verify repair —

20 Visually and physically inspect the fuel rail outlet

passages for a restriction.

Was a restriction found? — Verify repair Go to

Step 11

21 Is the fuel pressure indicated by the fuel pressure

gauge above the specified value? 0 kpa (0 psi) Go to

Step 22

Go to

Step 23

StepNoYesValue(s)Action

22 1.Command the fuel pump “ON” with the Tech 2.

2.Using suitable pliers which will not damage the fuel

hose, gradually apply pressure with the pliers to

pinch the flexible fuel return hose closed.

CAUTION:Do not let the fuel pressure exceed

the second specified value.

Does the fuel pressure indicated by the fuel pressure

gauge rise above the first specified value?

376 kpa (55

psi). 414 kpa

(60 psi). Go to

Step 11

Go to

Step 7

23 1. Command the fuel pump “ON” with the Tech 2.

2. Remove the fuel filler cap and listen for the sound of

the fuel pump running.

3. Turn the pump off.

Was the fuel pump running? —Go to

Step 7

Go to

Fuel

System

Electrical Test

Chart

Idle Air Control (IAC) System Check

Circuit Description

The Engine Control Module ECM controls engine idle

speed with the idle air control (IAC) valve. To increase idle

speed, the ECM retracts the IAC valve pintle away from

its seat, allowing more air to bypass the throttle bore. To

decrease idle speed, it extends the IAC valve pintle

towards its seat, reducing bypass air flow. A Tech 2 will

read the ECM commands to the IAC valve in counts.

Higher counts indicate more air bypass (higher idle).

Lower counts indicate less air is allowed to bypass (lower

idle).

Diagnostic Aids

A slow, unstable, or fast idle may be caused by a non-IAC

system problem that cannot be overcome by the IAC

valve. Out of control range IAC Tech 2 counts will be

above 60 if idle is too low, and zero counts if idle is too

high. The following checks should be made to repair a

non-IAC system problem:

DVacuum leak (high idle) – If idle is too high, stop the

engine. Fully extend (low) IAC with the IAC motor

analyzer 5-8840-2312-0. Start the engine. If idle

speed is above 800 RPM, locate and correct the

vacuum leak, including the PCV system. Check for

binding of the throttle blade or linkage.

DLean heated oxygen sensor signal (high air/fuel ratio) –

The idle speed may be too high or too low. Engine

speed may vary up and down, and disconnecting the

IAC valve does not help. Diagnostic trouble codes

P0131, P0151, P0171, or P0174 may be set. Tech 2

oxygen (O2) voltage will be less than 100 mV (0.1 V).

Check for low regulated fuel pressure, water in fuel, or

a restricted injector.

DRich heated oxygen sensor signal (low air/fuel ratio) –

The idle speed will be too low. Tech 2 IAC counts will

usually be above 80. The system is obviously rich and

may exhibit black smoke in the exhaust.

Tech 2 O2 voltage will be fixed at about 750 mV (0.75

V). Check for high fuel pressure, or a leaking or

sticking injector. A silicon-contaminated heated

oxygen sensor will show an O2 voltage slow to

respond on the Tech 2.

DThrottle body – Remove the IAC valve and inspect the

bore for foreign material.

DIAC valve electrical connections – IAC valve

connections should be carefully checked for proper

contact.

DPCV valve – An incorrect or faulty PCV valve may

result in an incorrect idle speed. Refer to

Diagnosis,

Rough Idle, Stalling

. If intermittent poor driveability or

idle symptoms are resolved by disconnecting the IAC,

carefully recheck the connections and valve terminal

resistance, or replace the IAC.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

1. The IAC motor analyzer 5-8840-2312-0 is used to

extend and retract the IAC valve. Valve movement

is verified by an engine speed change. If no change

in engine speed occurs, the valve can be resettled

when removed from the throttle body.

2. This step checks the quality of the IAC movement in

step 1. Between 700 revolutions per minute (RPM)

and about 1500 RPM, the engine speed should

change smoothly with each flash of the tester light

in both extend and retract. If the IAC valve is

retracted beyond the control range (about 1500

RPM), it may take many flashes to extend the IAC

valve before engine speed will begin to drop. This

is normal on certain engines. Fully extending the

IAC may cause engine stall. This may be normal.

6. Steps 1 and 2 verified the proper IAC valve

operation. This step checks the IAC circuits. Each

lamp on the noid light should flash red and green

while the IAC valve is cycled. While the sequence

of color is not important, if either light is “OFF” or

does not flash red and green, check the circuits for

faults, beginning with poor terminal contacts.

Idle Air Control (IAC) System Check

Step Action Value(s) Yes No

11. Ignition “OFF.”

2. Connect the IAC motor analyzer 5-8840-2312-0 to

the IAC valve.

3. Set the parking brake.

4. Block the wheels.

5. Turn the air conditioning “OFF.”

6. Idle the engine in Park (A/T) or Neutral (M/T).

7. Install the Tech 2. Display the RPM.

8. Use the IAC motor analyzer 5-8840-2312-0 to

extend and retract the IAC valve.

9. The engine speed should decrease and increase as

the IAC is cycled.

Does the RPM change? —Go to

Step 2

Go to

Step 3

2RPM should change smoothly with each flash of the

IAC motor analyzer 5-8840-2312-0 light.

Does the RPM change within the range specified? 700-1500

RPM Go to

Step 6

Go to

Step 3

3Check the IAC passages.

Are the IAC passages OK? —Go to

Step 4

Go to

Step 5

4Clear any obstruction from the IAC passages.

Is the action complete? — Verify repair —

5Replace the IAC. Refer to

On-V ehicle Service, Idle Air

Control Valve.

Is the action complete? — Verify repair —

61. Install the appropriate IAC noid light from

5-8840-2312-0 into the Engine Control Module

harness.

2. Cycle the IAC motor analyzer J 39027-A and

observe the noid lights.

3. Both the lights should cycle red and green, but

never “OFF,” as the RPM is changed over its range.

Do the noid lights cycle red and green? —Go to

Step 7

Go to

Step 8

71. Use the other connector on the IAC motor analyzer

5-8840-2312-0 pigtail.

2. Check the resistance across the IAC coils.

Measure the resistance between terminal A and

terminal B.

3. Measure the resistance between terminal C and

terminal D.

Is the resistance within the specified range? 40-80 ohms Go to

Step 9

Go to

Step 10

8If the circuits did not test green and red, check the

following:

DFaulty connector terminal contacts

DOpen circuits, including connections

DCircuits shorted to ground or voltage

DFaulty Engine Control Module connection or

Engine Control Module.

Are repairs necessary? —Go to

Step 13

—

Step NoYesValue(s)Action

91. Check the resistance between the IAC terminal B

and terminal C.

2. Check the resistance between the IAC terminal A

and terminal D.

Is the resistance infinite? —Go to

Step 11

Go to

Step 12

10 Replace the IAC. Refer to

On-V ehicle Service, Idle Air

Control Valve.

Is the action complete? —Go to

Step 7

—

11 Check the IAC valve and circuit.

Are the IAC valve and circuit OK? —

Refer to

Diagnostic

Aids

Go to

Step 12

12 Replace the IAC. Refer to

On-V ehicle Service, Idle Air

Control Valve

Is the action Complete? —Go to

Step 9

—

13 Repair as necessary.

Is the action complete? —Go to

Step 6

—

Barometric Pressure (BARO) Output Check

060RW072

Circuit Description

The barometric pressure (BARO) sensor measures the

changes in the intake BARO which result from engine

load (intake manifold vacuum) and engine speed

changes; and converts these into a voltage output. The

Engine Control Module ECM sends a 5-volt reference

voltage to the BARO sensor. As the BARO changes, the

output voltage of the sensor also changes. By monitoring

the the sensor output voltage, the ECM knows the BARO.

A lower pressure (low voltage) output voltage will be

about 1-2 volts at idle. Higher pressure (high voltage)

output voltage will be about 4-4.8 volts at wide open

throttle. The BARO sensor is also used, under certain

conditions, to measure barometric pressure, allowing the

ECM to make adjustments for different altitudes.

Test Description

IMPORTANT:Be sure to used the same diagnostic test

equipment for all measurements.

The number(s) below refer to the step number(s) on the

Diagnostic Chart.

1. Applying 34 kpa (10 Hg) vacuum to the BARO

sensor should cause the voltage to be 1.5-2.1 volts

less than the voltage at step 1. Upon applying

vacuum to the sensor, the change in voltage should

be instantaneous. A slow voltage change indicates

a faulty sensor.

IMPORTANT:Make sure the electrical connector

remains securely fastened.

2. Disconnect the sensor from the bracket. Twist the

sensor with your hand to check for an intermittent

connection. Output changes greater than 0.10 volt

indicate a bad sensor.

Barometric Pressure (BARO) Output Check

Step Action Value(s) Yes No

11. Turn the ignition “OFF” and leave it “OFF” for 15

seconds.

2. Ignition “ON.” Don’t crank engine.

3. The Tech 2 should indicate a barometric pressure

(BARO) sensor voltage.

4. Compare this scan reading to scan reading of a

known good vehicle obtained using the exact same

procedure as in Steps 1–4.

Is the voltage reading the same +/–0.40 volt? —Go to

Step 2

Go to

Step 5

21. Disconnect the BARO sensor and plug

inletmanifold.

2. Connect a hand vacuum pump to the BARO sensor.

3. Start the engine.

4. Apply 34 kpa (10 Hg) of vacuum and note the

voltage change.

Is the voltage change 1.5-2.1 volts less than step 1? —Go to

Step 3

Go to

Step 4

3No trouble found. Check the sensor cover for leakage

or restriction.

Does the cover supply vacuum to the BARO sensor

only? — Go to

Step 5

Go to

Step 4

4Repair the material to block.

Is the action complete? — Verify repair —

5Check the sensor connection.

Is the sensor connection good? —Go to

Step 5

Go to

Step 6

6Replace the sensor. Refer to

On-Vehicle Service,

BARO Sensor.

Is the action complete? — Verify repair —

7Repair the poor connection.

Is the action complete? — Verify repair —

ECM Diagnostic Trouble Codes

The following table lists the diagnostic trouble codes

supported a Tech 2 and to flash.If any DTCs not listed

here are displayed by a Tech 2, the Tech 2 data may be

faulty; notify the Tech 2 manufacturer of any DTCs

displayed that are not included in the following table.

ECM Diagnostic Trouble Codes

DTC

using a

Tech 2

Flash DTC Description Type Illuminate MIL

P0101 61 MAF System Performance BYes

P0102 61 MAF Sensor Circuit Low Frequency AYes

P0103 61 MAF Sensor Circuit High Frequency AYes

P0107 33 BARO Sensor Circuit Low Voltage AYes

P0108 33 BARO Sensor Circuit High Voltage AYes

P0112 23 IAT Sensor Circuit Low Voltage AYes

P0113 23 IAT Sensor Circuit High Voltage AYes

P0117 14 ECT Sensor Circuit Low Voltage AYes

P0118 14 ECT Sensor Circuit High Voltage AYes

P0121 21 TP System Performance AYes

P0122 21 TP Sensor Circuit Low Voltage AYes

P0123 21 TP Sensor Circuit High Voltage AYes

P0131 15 HO2S Circuit Low Voltage Bank 1 Sensor 1 AYes

P0132 15 HO2S Circuit High Voltage Bank 1 Sensor 1 AYes

P0134 15 HO2S Circuit Insufficient Activity Bank 1 Sensor 1 AYes

P0171 44 Fuel Trim System Lean Bank 1 BYes

P0172 45 Fuel Trim System Rich Bank 1 BYes

P0201 31 Injector 1 Control Circuit AYes

P0202 31 Injector 2 Control Circuit AYes

P0203 31 Injector 3 Control Circuit AYes

P0204 31 Injector 4 Control Circuit AYes

P0205 31 Injector 5 Control Circuit AYes

P0206 31 Injector 6 Control Circuit AYes

P0336 29 58X Reference Signal Circuit BYes

P0337 29 CKP Sensor Circuit Low Frequency BYes

P0341 41 CMP Sensor Circuit Performance BYes

P0342 41 CMP Sensor Circuit Low BYes

P0351 42 Ignition 1 Control Circuit AYes

P0352 42 Ignition 2 Control Circuit AYes

P0353 42 Ignition 3 Control Circuit AYes

P0354 42 Ignition 4 Control Circuit AYes

P0355 42 Ignition 5 Control Circuit AYes

P0356 43 Ignition 6 Control Circuit AYes

P0502 24 VSS Circuit Low Input BYes

P0562 66 System Voltage Low D No

P0563 66 System Voltage High D No

DTC

using a

Tech 2

Flash DTC Description Type Illuminate MIL

P0601 51 ECM Memory AYes

P1171 44 Fuel System Lean During Acceleration AYes

P1508 22 IAC System Low RPM BYes

P1509 22 IAC System High RPM BYes

P0101 MAF System Performance

060RW077

Circuit Description

The mass air flow (MAF) sensor measures the amount of

air which passes through it into the engine during a given

time. The Engine Control Module ECM uses the mass air

flow information to monitor engine operating conditions

for fuel delivery calculations. A large quantity of air

entering the engine indicates an acceleration or high load

situation, while a small quantity or air indicates

deceleration or idle.

The MAF sensor produces a frequency signal which can

be monitored using a Tech 2. The frequency will vary

within a range of around 4 to 7 g/s at idle to around 25 to 40

g/s at maximum engine load. DTC P0101 will be set if the

signal from the MAF sensor does not match a predicted

value based on throttle position and engine RPM.

Conditions for Setting the DTC

DThe engine is running.

DNo TP sensor or BARO, CMP, CKP, MAF sensor DTCs

are set.

DThe Engine Speed is between 2800 r.p.m and 4500

r.p.m.

DTP angle is between 1V and 3V.

DIAT is between —14°C and 70°C.

DAbove conditions present for at least 3 second.

DMAF signal frequency indicates an airflow significantly

higher or lower than a predicted value based on throttle

position and engine RPM for a total of 12.5 seconds

over a 25-second period of time.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) after the second consecutive trip in which the

fault is detected.

DThe ECM calculates an airflow value based on idle air

control valve position, throttle position, RPM and

barometric pressure.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0101 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0101 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

An intermittent may be caused by the following:

DPoor connections.

DMis-routed harness.

DRubbed through wire insulation.

DBroken wire inside the insulation.

Refer to Intermittents under service category Symptoms.

Any un-metered air may cause this DTC to set. Check for

the following:

DThe duct work at the MAF sensor for leaks.

DAn engine vacuum leak.

DThe PCV system for vacuum leaks.

DAn incorrect PCV valve.

DThe engine oil dip stick not fully seated.

DThe engine oil fill cap loose or missing.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. Using Freeze Frame and/or Failure Records data

may aid in locating an intermittent condition. If the

DTC cannot be duplicated, the information included

in the Freeze Frame and/or Failure Records data

can be useful in determining how many miles since

the DTC set. The Fail Counter and Pass Counter

can also be used to determine how many ignition

cycles the diagnostic reported a pass and/or a fail.

Operate the vehicle within the same Freeze Frame

conditions (RPM, load, vehicle speed , temperature,

etc.) that were noted. This will isolate when the

DTC failed.

For any test that requires back probing the ECM or

component harness connectors, use the Connector

Test Adapter Kit 5-8840-0385-0. Using this kit will

prevent any damage to the harness connector

terminals.

3. Any un-metered air may cause this DTC to set.

Check the PVC system for vacuum leaks. Also

inspect the dip stick for being pulled out. Check the

oil fill cap for being loose.

4. Verifies the signal circuit from the MAF sensor

electrical connector to the ECM.

5. Verifies whether a ground and B+ circuit is available.

6. Checks a signal circuit for an open.

7. Checks for a signal circuit shorted to B+.

DTC P0101 – MAF System Performance

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. Review the Freeze Frame and/or Failure Records

data for this DTC and note parameters.

3. Ignition “OFF” for 15 seconds.

4. Start the engine and operate the vehicle within the

conditions required for this diagnostic to run, and as

close to the conditions recorded in Freeze Frame

/Failure Records possible. (Special operating

conditions that need to be met before the ECM will

run this diagnostic (where applicable) are listed in

“Conditions for Setting the DTC”).

5. Using the Tech 2, select “DTC,” then enter the DTC

number which was set.

Does the Tech 2 indicate that this diagnostic failed this

ignition? — Go to

Step 3

Refer to

Diagnostic

Aids

31. Check for the following conditions:

DObjects blocking the MAF sensor inlet screen;

DIntake manifold vacuum leaks;

DVacuum leaks at throttle body;

DCrankcase ventilation valve faulty, missing, or

incorrectly installed.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 4

Step NoYesValue(s)Action

41. Ignition “OFF.”

2. Disconnect the MAF sensor connector.

3. Ignition “ON,” engine “OFF.”

4. Using DVM 5-8840-0285-0, measure voltage

between the MAF sensor signal circuit and chassis

ground.

Is the voltage near the specified value? 5 V Go to

Step 5

Go to

Step 6

5Connect a test light (5-8840-0607-0) between the MAF

sensor ignition feed and ground circuits at the MAF

sensor harness connector.

Is the test light “ON?” —Go to

Step 9

Go to

Step 8

6Is the voltage less than the specified value? 4.5 V Go to

Step 14

Go to

Step 7

71. Ignition “OFF,” disconnect the ECM.

2. Ignition “ON,” engine “OFF.”

3. Measure voltage between the MAF signal circuit

and ground.

Does the voltage measure near the specified value? 0 V Go to

Step 20

Go to

Step 17

8Connect a test light (5-8840-0607-0) between the MAF

sensor ignition feed circuit and chassis ground.

Is the test light “ON?” —Go to

Step 9

Go to

Step 10

91. Check for a poor connection at the MAF sensor.

2. If a poor connection is found, replace faulty

terminal(s).

Was a poor connection found? — Verify repair Go to

Step 10

10 1. Check the MAF sensor damage.

2. If the MAF sensor damage is found, replace the

MAF sensor.

Was the MAF sensor damage found? — Verify repair Go to

Step 11

11 Replace the ECM.

Is the action complete? — Verify repair —

P0102 MAF Sensor Circuit Low Frequency

060RW077

Circuit Description

The mass air flow (MAF) sensor measures the amount of

air which passes through it into the engine during a given

time. The Engine Control Module ECM uses the mass air

flow information to monitor engine operating conditions

for fuel delivery calculations. A large quantity of air

entering the engine indicates an acceleration or high load

situation, while a small quantity of air indicates

deceleration or idle.

The MAF sensor produces a frequency signal which can

be monitored using a Tech 2. The frequency will vary

within a range of around 4 to 7 g/s at idle to around 25 to 40

g/s at maximum engine load. DTC P0102 will be set if the

signal from the MAF sensor is below the possible range of

a normally operating MAF sensor.

Conditions for Setting the DTC

DThe engine is running between 500 and 2000 RPM for

greater than 2 seconds.

DSystem voltage is under 300m volts.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM calculates an air flow value based on idle air

control valve position, throttle position, RPM and

barometric pressure.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0102 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0102 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

locks, improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DMisrouted harness – Inspect the MAF sensor harness

to ensure that it is not routed too close to high voltage

wires.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

Tech 2 while moving connectors and wiring harnesses

related to the MAF sensor . A change in the display will

indicate the location of the fault.

DPlugged intake air duct or filter element – A wide-open

throttle acceleration from a stop should cause the

mass air flow displayed on a Tech 2 to increase from

about 3-6 g/second at idle to 100 g/second or greater

at the time of the 1-2 shift. If not, check for a restriction.

If DTC P0102 cannot be duplicated, the information

included in the Failure Records data can be useful in

determining vehicle mileage since the DTC was last set.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. This step verifies that the problem is present at idle.

4. A voltage reading of less than 4 or over 5 volts at the

MAF sensor signal circuit indicates a fault in the

wiring or a poor connection.

5. This verifies that ignition feed voltage and a good

ground are available at the MAF sensor.

DTC P0102 – MAF Sensor Circuit Low Frequency

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Start the engine.

2. With the engine idling, monitor “MAF Frequency”

display on the Tech 2.

Is the “MAF Frequency” below the specified value? 4 ∼ 7 g/s Go to

Step 4

Go to

Step 5

31. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor “Specific DTC” info for DTC

P0102.

Does the Tech 2 indicate DTC P0102 failed this

ignition? — Go to

Step 4

Refer to

Diagnostic

Aids

41. Ignition “OFF.”

2. Disconnect the MAF sensor connector.

3. Ignition “ON,” engine “OFF.”

4. Using a DVM, measure voltage between the MAF

sensor signal circuit and battery ground.

Is the voltage near the specified value? 5 V Go to

Step 5

Go to

Step 8

5Connect a test light between the MAF sensor ignition

feed and ground circuits at the MAF sensor harness

connector.

Is the test light “ON?” —Go to

Step 13

Go to

Step 6

6Connect a test light between the MAF sensor ignition

feed circuit and battery ground.

Is the test light “ON?” —Go to

Step 12

Go to

Step 7

71. Check for a poor connection at the MAF sensor.

2. If a poor connection is found, replace the faulty

terminal(s).

Was a poor connection found? — Verify repair Go to

Step 11

Step NoYesValue(s)Action

81. Ignition “OFF.”

2. Disconnect the MAF sensor.

3. Disconnect the ECM connector for the MAF signal

circuit.

4. Ignition “ON,” engine “OFF.”

5. With the DVM, measure the voltage between the

MAF signal terminal at the ECM and battery ground.

Is the voltage under the specified value? 4 V Go to

Step 9

Go to

Step 10

91. Ignition “OFF.”

2. Disconnect the ECM white connector.

3. Ignition “ON.”

4. Check the MAF sensor signal circuit for a short to 5

volts.

Is the action complete? — Verify repair —

10 1. Ignition “OFF.”

2. Disconnect the ECM white connector.

3. Ignition “ON.”

4. Check the MAF sensor signal circuit between the

ECM and the MAF sensor for an open, short to

ground, or short to the MAF ground circuit.

Is the action complete? — Verify repair Go to

Step 13

11 Locate and repair the open in the ground circuit to the

MAF sensor.

Is the action complete? — Verify repair —

12 Locate and repair the open in the ignition feed circuit to

the MAF sensor.

Is the action complete? — Verify repair —

13 Replace the MAF sensor.

Is the action complete? — Verify repair Go to

Step 14

14 Replace the ECM.

Is the action complete? — Verify repair —

P0103 MAF Sensor Circuit High Frequency

060RW077

Circuit Description

The mass air flow (MAF) sensor measures the amount of

air which passes through it into the engine during a given

time. The Engine Control Module ECM uses the mass air

flow information to monitor engine operating conditions

for fuel delivery calculations. A large quantity of air

entering the engine indicates an acceleration or high load

situation, while a small quantity of air indicates

deceleration or idle.

The MAF sensor produces a frequency signal which can

be monitored using a Tech 2. The frequency will vary

within a range of around 4 ∼ 7 g/s at idle to around 25 to 40

g/s at maximum engine load. DTC P0103 will be set if the

signal from the MAF sensor is above the possible range of

a normally operating MAF sensor.

Conditions for Setting the DTC

DThe engine is running between 500 and 2000 RPM for

more than 2 seconds.

DSystem voltage is above 5000m volts.

DAbove conditions present for at least 961m sec.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM calculates an airflow value based on idle air

control valve position, throttle position, RPM and

barometric pressure.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0103 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0103 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

If DTC P0103 cannot be duplicated, the information

included in the Failure Records data can be useful in

determining vehicle mileage since the DTC was last set.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. This step verifies that the problem is present at idle.

4. A frequency reading with the MAF sensor connector

disconnected indicates an electromagnetic

interference (EMI) related fault.

DTC P0103 – MAF Sensor Circuit High Frequency

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor “DTC” info for DTC P0103.

Does the Tech 2 indicate DTC P0103 failed this

ignition? — Go to

Step 3

Refer to

Diagnostic

Aids

31. Start the engine.

2. With the engine idling, monitor “MAF Frequency”

display on the Tech 2.

Is “MAF Frequency” above the specified value? 25 to 40 g/s Go to

Step 4

Go to

Step 7

41. Ignition “OFF.”

2. Disconnect the MAF sensor connector.

3. Ignition “ON,” engine idling.

4. Using a Tech 2, monitor “MAF Frequency.”

Does the Tech 2 indicate a “MAF Frequency” at the

specified value? 0 g/s Go to

Step 5

Go to

Step 6

5Replace the MAF sensor.

Is the action complete? — Verify repair Go to

Step 8

61. Check the MAF harness for incorrect routing near

high voltage components (solenoids, relays,

motors).

2. If incorrect routing is found, correct the harness

routing.

Was a problem found? — Verify repair Go to

Step 6

71. With the engine idling, monitor “MAF Frequency”

display on the Tech 2.

2. Quickly snap open throttle to wide open throttle

while under a road load and record value.

Does the Tech 2 indicate “MAF Frequency” above the

specified value? 25 to 40 g/s Go to

Step 5

Go to

Step 8

8Replace the ECM.

Is the action complete? — Verify repair —

P0107 BARO Sensor Circuit Low Voltage

060RW072

Circuit Description

The barometric pressure (BARO) sensor responds to

changes in intake manifold pressure (vacuum). The

BARO sensor signal voltage to the Engine Control

Module ECM varies from below 2 volts at idle (high

vacuum) to above 4 volts with the ignition “ON,” engine

not running or at wide-open throttle (low vacuum).

The ECM monitors the BARO signals for voltages outside

the normal range of the BARO sensor. If the ECM detects

a BARO signal voltage that is excessively low, DTC

P0107 will be set.

Conditions for Setting the DTC

DIgnition SW is ON.

DAbove conditions present for at least 19 second.

DThe BARO sensor voltage under 100m volts.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will default to a BARO value of 79.3 kpa.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0107 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0107 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DCheck for intermittent codes.

DThe BARO sensor shares a ground with the ECT

sensor, and the Transmission Fluid Temperature

sensor.

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

locks, improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

BARO display on the Tech 2 while moving connectors

and wiring harnesses related to the sensor . A change

in the display will indicate the location of the fault.

If DTC P0107 cannot be duplicated, the information

included in the Failure Records data can be useful in

determining vehicle mileage since the DTC was last set.

If it is determined that the DTC occurs intermittently,performing the DTC P0107 Diagnostic Chart may isolate

the cause of the fault.

DTC P0107 – BARO Sensor Circuit Low Voltage

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. With the throttle closed, observe the BARO value

displayed on the Tech 2.

Is the BARO value near the specified value? 11 kpa at sea

level Go to

Step 4

Go to

Step 3

31. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor “DTC” info for DTC P0107.

Does the Tech 2 indicate DTC P0107 failed? —Go to

Step 4

Refer to

Diagnostic

Aids

41. Ignition “OFF.”

2. Disconnect the BARO sensor electrical connector.

3. Jumper the 5 volt reference “A” circuit and the

BARO signal together at the BARO sensor harness

connector.

4. Ignition “ON.”

5. Observe the BARO value displayed on the Tech 2.

Is the BARO value near the specified value? 5 V 104 kpa Go to

Step 10

Go to

Step 5

51. Disconnect the jumper.

2. Connect a test light between B+ and the BARO

sensor signal circuit at the BARO sensor harness

connector.

3. Observe the BARO value displayed on the Tech 2.

Is the BARO value near the specified value. 5 V 104 kpa Go to

Step 6

Go to

Step 8

61. Ignition “OFF.”

2. Disconnect the ECM and check the 5 volt reference

“A” circuit for an open or short to ground.

3. If the 5 volt reference “A” circuit is open or shorted to

ground, repair it as necessary.

Was the 5 volt reference “A” circuit open or shorted to

ground? — Verify repair Go to

Step 7

7Check the 5 volt reference “A” circuit for a poor

connection at the ECM and replace the terminal if

necessary.

Did the terminal require replacement? — Verify repair Go to

Step 11

81. Ignition “OFF.”

2. Disconnect the ECM, and check the BARO signal

circuit for an open, short to ground, or short to the

sensor ground circuit.

3. If the BARO sensor signal circuit is open or shorted

to ground, repair it as necessary.

Was the BARO signal circuit open or shorted to

ground? —Verify repair Go to

Step 9

Step NoYesValue(s)Action

9Check the BARO sensor signal circuit for a poor

connection at the ECM and the BARO sensor; replace

the terminal if necessary.

Did the terminal require replacement? — Verify repair Go to

Step 11

10 Replace the BARO sensor.

Is the action complete? — Verify repair —

11 Replace the ECM.

Is the action complete? — Verify repair —

P0108 BARO Sensor Circuit Hight Voltage

060RW072

Circuit Description

The barometric pressure (BARO) sensor responds to

changes in intake manifold pressure (vacuum). The

BARO sensor signal voltage to the Engine Control

Module ECM varies from below 2 volts at idle (high

vacuum) to above 4 volts with the key “ON,” engine not

running or at wide- open throttle (low vacuum).

The ECM monitors the BARO signals for voltages outside

the normal range of the BARO sensor. If the ECM detects

a BARO signal voltage that is excessively high, DTC

P0108 will be set.

Conditions for Setting the DTC

DIgnition SW is ON.

DThe BARO sensor voltage more than 5100V.

DAbove conditions present for at least 19 second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will default to a BARO value of 79.3 kpa.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0108 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0108 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

locks, improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

BARO display on the Tech 2 while moving connectors

and wiring harnesses related to the sensor . A change

in the display will indicate the location of the fault.

If DTC P0108 cannot be duplicated, the information

included in the Failure Records data can be useful in

determining vehicle mileage since the DTC was last set. If

it is determined that the DTC occurs intermittently,

performing the DTC P1108 Diagnostic Chart may isolate

the cause of the fault.

DTC P0108 – BARO Sensor Circuit High Voltage

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. If the engine idle is rough, unstable or incorrect,

repair the idle problem before using this chart. Refer

Symptoms

section.

2. With the engine idling, note the BARO value on the

Tech 2.

Is the BARO reading above the specified value? 90 kpa Go to

Step 4

Go to

Step 3

31. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor “ DTC” info for DTC P0108.

Does the Tech 2 indicate DTC P0108 failed this

ignition? — Go to

Step 4

Refer to

Diagnostic

Aids

41. Ignition “OFF.”

2. Disconnect the BARO sensor electrical connector.

3. Ignition “ON.”

4. Note the BARO sensor voltage displayed on the

Tech 2.

Is the BARO sensor voltage at the specified value? 0.0 V 11 kpa Go to

Step 5

Go to

Step 6

5Probe the sensor ground circuit with a test light to B+.

Is the test light “ON?” —Go to

Step 7

Go to

Step 9

61. Check the BARO signal circuit for a short to voltage

or a short to the 5 volt reference “A” circuit.

2. If the BARO sensor signal circuit is shorted, repair

circuit as necessary.

Was the BARO sensor signal circuit shorted? — Verify repair Go to

Step 11

71. Check for a poor sensor ground terminal connection

at the BARO sensor electrical connector.

2. If a problem if found, replace the faulty terminal.

Did the terminal require replacement? — Verify repair Go to

Step 8

8Check for a plugged or leaking vacuum supply to the

BARO sensor.

Is the vacuum supply plugged or leaking? — Verify repair Go to

Step 12

91. Check for a poor sensor ground terminal connection

at the ECM.

2. If a problem is found, replace the faulty terminal.

Did the terminal require replacement? — Verify repair Go to

Step 10

10 1. Check the continuity of the BARO sensor ground

circuit.

2. If the BARO sensor ground circuit measures over 5

ohms, repair open or poor connection.

Was a condition found and corrected? — Verify repair Go to

Step 11

Step NoYesValue(s)Action

11 Replace the ECM.

Is the action complete? —Verify Repair —

12 Replace the BARO sensor.

Is the action complete? — Verify repair —

P0112 IAT Sensor Circuit Low Voltage

060RW057

Circuit Description

The intake air temperature (IAT) sensor is a thermistor

which measures the temperature of the air entering the

engine. The Engine Control Module ECM applies 5 volts

through a pull-up resistor to the IAT sensor. When the

intake air is cold, the sensor resistance is high and the

ECM will monitor a high signal voltage on the IAT signal

circuit. If the intake air is warm, the sensor resistance is

lower , causing the ECM to monitor a lower voltage. DTC

P0112 will set when the ECM detects an excessively low

signal voltage on the intake air temperature sensor signal

circuit.

Conditions for Setting the DTC

DIgnition SW is ON.

DIAT signal voltage is under 160m volts.

DAbove conditions present for at least 5 second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0112 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0112 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

locks, improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

IA T display on the T ech 2 while moving connectors and

wiring harnesses related to the IAT sensor. A change

in the IAT display will indicate the location of the fault.

If DTC P0112 cannot be duplicated, the information

included in the Failure Records data can be useful in

determining vehicle mileage since the DTC was last set.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart:

2. Verifies that the fault is present.

3. If DTC P0112 can be repeated only by duplicating

the Failure Records condition, refer to the

Temperature vs. Resistance Value

table. The table

may be used to test the IAT sensor at various

temperatures to evaluate the possibility of a

“shifted” sensor that may be stored above or below

a certain temperature. If this is the case, replace

the IAT sensor. If the IAT sensor appears to be OK,

the fault is intermittent; refer to

Diagnostic Aids

Intake Air Temperature Sensor

°C°F OHMS

Temperature vs. Resistance Values

(approximate)

100 212 177

80 176 332

60 140 667

45 113 1188

35 95 1802

25 77 2796

15 59 4450

5 41 7280

–5 23 12300

–15 5 21450

–30 –22 52700

–40 –40 100700

DTC P0112 – IAT Sensor Circuit Low Voltage

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. Using a Tech 2, monitor the intake air temperature

(IAT).

Is the intake air temperature greater than the specified

value? 148°C

(283°F) Go to

Step 4

Go to

Step 3

31. Ignition “ON,” engine “OFF.” Review and record

Tech 2 Failure Records data.

2. Operate the vehicle within Failure Records

conditions as noted.

3. Using a Tech 2, monitor the “ DTC” info for DTC

P0112.

Does the Tech 2 indicate DTC P0112 failed this

ignition? —Refer to

Test

Description

Refer to

Diagnostic

Aids

41. Ignition “OFF.”

2. Disconnect the IAT sensor electrical connector.

3. Ignition “ON.”

4. Observe the intake air temperature on the Tech 2.

Is the intake air temperature below the specified value? –38°C

(–36°F) Go to

Step 6

Go to

Step 5

51. Ignition “OFF.”

2. Disconnect the ECM electrical connectors.

3. Check the IAT sensor signal circuit for a short to

ground.

Is the IAT sensor signal circuit shorted to ground? — Verify repair Go to

Step 7

6Replace the IAT sensor.

Is the action complete? — Verify repair —

7Replace the ECM.

Is the action complete? — Verify repair —

P0113 IAT Sensor Circuit High Voltage

060RW057

Circuit Description

The intake air temperature (IAT) sensor is a thermistor

which measures the temperature of the air entering the

engine. The Engine Control Module ECM applies 5 volts

through a pull-up resistor to the IAT sensor. When the

intake air is cold, the sensor resistance is high and the

ECM will monitor a high signal voltage on the IAT signal

circuit. If the intake air is warm, the sensor resistance is

lower causing the ECM to monitor a lower voltage. DTC

P01 13 will set when the ECM detects an excessively high

signal voltage on the intake air temperature sensor signal

circuit.

Conditions for Setting the DTC

DIgnition SW is ON.

DThe ECT sensor voltage more than 5000m volts.

DAbove conditions present for at least 5 second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0113 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0113 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

locks, improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

IA T display on the T ech 2 while moving connectors and

wiring harnesses related to the IAT sensor. A change

in the IAT display will indicate the location of the fault.

If DTC P0113 cannot be duplicated, the information

included in the Failure Records data can be useful in

determining vehicle mileage since the DTC was last set.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart:

2. Verifies that the fault is present.

3. If DTC P0113 can be repeated only by duplicating

the Failure Records conditions, refer to the

“Temperature vs. Resistance Values” table. The

table may be used to test the IAT sensor at various

temperatures to evaluate the possibility of a

“shifted” sensor that may be open above or below a

certain temperature. If this is the case, replace the

IAT sensor. If the IAT sensor appears to be OK, the

fault is intermittent; refer to

Diagnostic Aids

Intake Air Temperature Sensor

°C°F OHMS

Temperature vs. Resistance Values

(approximate)

100 212 177

80 176 332

60 140 667

45 1131188

35 95 1802

25 77 2796

15 59 4450

5 41 7280

–5 23 12300

–15 5 21450

–30 –22 52700

–40 –40 100700

DTC P0113 –IAT Sensor Circuit High Voltage

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Ignition “ON,” engine “OFF.” Observe the “Intake Air

Temp” display on the Tech 2.

Is the “Intake Air Temp” below the specified value? –38°C

(–36°F) Go to

Step 4

Go to

Step 3

31. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data

parameters.

3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor “ DTC” info for DTC P01 13.

Does the Tech 2 indicate DTC P0113 failed? —Refer to

Test

Description

Refer to

Diagnostic

Aids

41. Ignition “OFF.”

2. Disconnect the IAT sensor electrical connector.

3. Jumper the IA T signal circuit and the sensor ground

circuit together at the IAT sensor harness

connector.

4. Ignition “ON.”

5. Observe the “Intake Air Temp” display on the Tech

Is the “Intake Air Temp” at the specified value? 140°C

(284°F) Go to

Step 6

Go to

Step 5

51. Jumper the IAT signal circuit at the IAT sensor

harness connector to chassis ground.

2. Observe the “Intake Air Temp” display on the Tech

Is the “Intake Air Temp” at the specified value? 140°C

(284°F) Go to

Step 7

Go to

Step 8

Step NoYesValue(s)Action

6Check for poor connections at the IAT sensor and

replace terminals if necessary.

Did any terminals require replacement? — Verify repair Go to

Step 10

71. Ignition “OFF.”

2. Disconnect the ECM, and check the IAT sensor

ground circuit for an open.

3. If the IAT sensor ground circuit is open, repair it as

necessary.

Was the IAT sensor ground circuit open? — Verify repair Go to

Step 9

81. Ignition “OFF.”

2. Disconnect the ECM, and check the IAT signal

circuit for an open.

3. If the IAT sensor signal circuit is open, repair it as

necessary.

Was the IAT signal circuit open? — Verify repair Go to

Step 9

9Check for a poor sensor ground or IAT signal circuit

terminal connection at the ECM and replace

terminal(s) if necessary.

Did any of the terminals need to be replaced? — Verify repair Go to

Step 11

10 Replace the IAT sensor.

Is the action complete? — Verify repair —

11 Replace the ECM.

Is the action complete? — Verify repair —

P0117 ECT Sensor Circuit Low Voltage

060RW072

Circuit Description

The engine coolant temperature (ECT) sensor is a

thermistor mounted on a coolant crossover pipe at the

rear of the engine. The Engine Control Module ECM

applies a voltage (about 5 volts) through a pull-up resistor

to the ECT signal circuit. When the engine coolant is cold,

the sensor (thermistor) resistance is high, therefore the

ECM will measure a high signal voltage. As the engine

coolant warms, the sensor resistance becomes lower,

and the ECT signal voltage measured at the ECM drops.

With a fully warmed-up engine, the ECT signal voltage

should measure about 1.5 to 2.0 volts.

Conditions for Setting the DTC

DIgnition SW is ON.

DThe ECT sensor voltage is under 80m volts.

DAbove conditions present for at least 5 second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will substitute the ECT reading with a default

engine coolant temperature value. The default value

is based on start-up intake air temperature and running

time.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0117 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0117 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

locks, improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

ECT display on the Tech 2 while moving connectors

and wiring harnesses related to the ECT sensor. A

change in the ECT display will indicate the location of

the fault.

If DTC P0117 cannot be duplicated, the information

included in the Failure Records data can be useful in

determining vehicle mileage since the DTC was last set.

If it is determined that the DTC occurs intermittently.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. Verifies that the fault is present.

3. If DTC P0117 can be repeated only by duplicating

the Failure Records conditions, refer to the

“Temperature vs. Resistance Values” table. The

table may be used to test the ECT sensor at various

temperatures to evaluate the possibility of a

“shifted” sensor that may be shorted above or below

a certain temperature. If this is the case, replace

the ECT sensor. If the ECT sensor appears to be

OK, the fault is intermittent; refer to

Diagnostic Aids

Engine Coolant Temperature Sensor

°C°F OHMS

Temperature vs. Resistance Values

(approximate)

100 212 177

80 176 332

60 140 667

45 1131188

35 95 1802

25 77 2796

15 59 4450

5 41 7280

–5 23 12300

–15 5 21450

–30 –22 52700

–40 –40 100700

DTC P0117 – ECT Sensor Low Voltage

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. Observe the “Eng Cool T emp” display on the T ech 2.

Is the “Eng Cool Temp” below the specified value? 139°C

(282°F) Go to

Step 4

Go to

Step 3

31. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor “ DTC” info for DTC P01 17.

Does the Tech 2 indicate DTC P0117 failed this

ignition? — Go to

Step 4

Refer to

Diagnostic

Aids

41. Disconnect the ECT sensor electrical connector.

2. Observe the “Eng Cool T emp” display on the T ech 2.

Is the “Eng Cool Temp” at the specified value? –39°C

(–38°F) Go to

Step 6

Go to

Step 5

51. Ignition “OFF.”

2. Disconnect the ECM and check the ECT signal

circuit for a short to ground or a short to the sensor

ground circuit.

3. If the ECT signal circuit is shorted. repair it as

necessary.

Was the ECT signal circuit shorted to ground? — Verify repair Go to

Step 7

6Replace the ECT sensor.

Is the action complete? — Verify repair —

7Replace the ECM.

Is the action complete? — Verify repair —

P0118 ECT Sensor Circuit High Voltage

060RW072

Circuit Description

The engine coolant temperature (ECT) sensor is a

thermistor mounted in on a coolant crossover pipe at the

rear of the engine. The Engine Control Module ECM

applies a voltage (about 5 volts) through a pull-up resistor

to the ECT signal circuit. When the engine coolant is cold,

the sensor (thermistor) resistance is high, therefore the

ECM will measure a high signal voltage. As the engine

coolant warms, the sensor resistance becomes less, and

the ECT signal voltage measured at the ECM drops. With

a fully warmed-up engine, the ECT signal voltage should

measure about 1.5 to 2.0 volts.

Conditions for Setting the DTC

DIgnition SW is ON.

DThe ECT sensor voltage more than 5000m volts.

DAbove conditions present for at least 5 second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will substitute the ECT reading with a default

engine coolant temperature value. The default value

is based on start-up intake air temperature and running

time.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0118 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0118 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

locks, improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

ECT display on the Tech 2 while moving connectors

and wiring harnesses related to the ECT sensor. A

change in the ECT display will indicate the location of

the fault.

If DTC P0118 cannot be duplicated, the information

included in the Failure Records data can be useful in

determining vehicle mileage since the DTC was last set.

If it is determined that the DTC occurs intermittently,

performing the DTC P1115 Diagnostic Chart may isolate

the cause of the fault.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. Verifies that the fault is present.

3. If DTC P0118 can be repeated only by duplicating

the Failure Records conditions, refer to the

“Temperature vs. Resistance Value” table. The

table may be used to test the ECT sensor at various

temperatures to evaluate the possibility of a

“shifted” sensor that may be shorted above or below

a certain temperature. If this is the case, replace

the ECT sensor. If the ECT sensor appears to be

OK, the fault is intermittent; refer to

Diagnostic Aids

Engine Coolant Temperature Sensor

°C°F OHMS

Temperature vs. Resistance Values

(approximate)

100 212 177

80 176 332

60 140 667

45 113 1188

35 95 1802

25 77 2796

15 59 4450

5 41 7280

–5 23 12300

–15 5 21450

–30 –22 52700

–40 –40 100700

DTC P0118 – ECT Sensor Circuit High Voltage

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. Observe the “Eng Cool T emp” display on the T ech 2.

Is the “Eng Cool Temp” below the specified value? –39°C

(–38°F) Go to

Step 4

Go to

Step 3

31. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor the “ DTC” info for DTC

P0118.

Does the Tech 2 indicate DTC P0118 failed? —Refer to

Test

Description

Refer to

Diagnostic

Aids

41. Disconnect the ECT sensor electrical connector.

2. Jumper the ECT signal circuit and the sensor

ground circuit together at the ECT sensor harness

connector.

3. Observe the “Eng Cool T emp” display on the T ech 2.

Is the “Eng Cool Temp” at the specified value? 140°C

(284°F) Go to

Step 6

Go to

Step 5

51. Jumper the ECT signal circuit at the ECT sensor

harness connector to chassis ground.

2. Observe the “Eng Cool T emp” display on the T ech 2.

Is the “Eng Cool Temp” at the specified value? 140°C

(284°F) Go to

Step 7

Go to

Step 8

6Check for poor connections at the ECT sensor and

replace terminals if necessary.

Did any terminals require replacement? — Verify repair Go to

Step 10

71. Ignition “OFF.”

2. Disconnect the ECM, and check the ECT sensor

ground circuit for an open.

3. If the ECT sensor ground circuit is open, repair it as

necessary.

Was the ECT sensor ground circuit open? — Verify repair Go to

Step 9

81. Ignition “OFF.”

2. Disconnect the ECM, and check the ECT signal

circuit for an open.

3. If the ECT sensor signal circuit is open, repair it as

necessary.

Was the ECT signal circuit open? — Verify repair Go to

Step 9

9Check for a poor sensor ground or ECT signal circuit

terminal connection at the ECM and replace

terminal(s) if necessary.

Did any of the terminals need to be replaced? — Verify repair Go to

Step 11

10 Replace the ECT sensor.

Is the action complete? — Verify repair —

11 Replace the ECM.

Is the action complete? — Verify repair —

P0121 TP System Performance

060RW077

Circuit Description

The throttle position (TP) sensor circuit provides a voltage

signal that changes relative to throttle blade angle. The

signal voltage will vary from about 0.6 volts at closed

throttle to about 4.5 volts at wide open throttle (WOT).

The TP signal is one of the most important inputs used by

the Engine Control Module ECM for fuel control and many

of the ECM-controlled outputs. The ECM monitors

throttle position and compares actual throttle position

from the TP sensor to a predicted TP value calculated

from engine speed. If the ECM detects an out-of-range

condition, DTC P0121 will set.

Conditions for Setting the DTC

DThe engine is running.

DNo BARO/ECT/MAF/CKP/CMP DTCs, or P0122,

P0123 DTCs are set.

DBARO reading is below 3000m volts.

DThrottle is steady, throttle angle is changing less than

1%.

DECT reading more than 75°C.

DAbove conditions present for at least second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) after the second consecutive trip in which the

fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

DThe ECM will use a default throttle position based on

mass air flow and RPM.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0121 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0121 can be cleared by using the Tech 2 “Clear

info ” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DSkewed BARO signal or faulty BARO sensor – An

incorrect BARO signal may cause the ECM to

incorrectly calculate the predicted TP sensor value

during high engine load situations. Check for an

unusually low BARO reading. This condition can

cause DTC P0121 to be set.

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

locks improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

ECT display on the Tech 2 while moving connectors

and wiring harnesses related to the sensor. A change

in the display will indicate the location of the fault. If DTC P0121 cannot be duplicated, the information

included in the Failure Records data can be useful in

determining vehicle mileage since the DTC was last set.

DTC P0121 –TP System Performance

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine not running.

2. Observe the BARO reading on the Tech 2.

Is the BARO reading less than the specified value? 65 kpa Go to

Step 3

Go to

Step 6

31. Disconnected the BARO sensor.

2. Connect a test light between the 5 volt reference “A”

circuit and the BARO signal circuit at the BARO

sensor harness connector.

3. Observe the BARO reading on the Tech 2.

Is the BARO reading less than the specified value? 65 kpa Go to

Step 5

Go to

Step 4

41. Check the BARO signal circuit between the ECM

and the BARO sensor for an open, short to ground,

or short to the BARO ground circuit.

2. If the BARO signal circuit is open or shorted, repair it

as necessary.

Was the BARO signal circuit open or shorted? — Verify repair Go to

Step 12

5Replace the BARO sensor.

Is the action complete? — Verify repair —

6Observe the TP angle reading on the Tech 2 while

slowly opening the throttle.

Does the TP angle increase steadily and evenly from

the closed throttle value to the wide open throttle

value?

Closed

throttle = 0%

Wide open

throttle =

100%

Refer to

Diagnostic

Aids

Go to

Step 7

71. Disconnect the TP sensor.

2. Observe the TP sensor reading on the Tech 2.

Is the TP sensor reading near the specified value? 0 V Go to

Step 8

Go to

Step 9

81. Connect a test light between the 5 volt reference “A”

circuit and the TP sensor signal circuit at the TP

sensor harness connector.

2. Observe the TP sensor reading on the Tech 2.

Is the TP sensor reading at the specified value? 5 V Go to

Step 11

Go to

Step 10

9Check the following items:

1. TP signal circuit for a short to voltage.

2. TP sensor ground circuit for high resistance

between the ECM and the TP sensor.

3. TP sensor ground circuit for a poor connection.

4. If a problem is found, repair wiring harness as

necessary.

Was a problem found? — Verify repair Go to

Step 12

Step NoYesValue(s)Action

10 Check the following items:

1. TP signal circuit or 5 volt reference “A” circuit for a

poor connection.

2. TP signal circuit or 5 volt reference “A” circuit for

high resistance between the ECM and the TP

sensor.

3. If a problem is found, repair wiring harness as

necessary.

Was a problem found? — Verify repair Go to

Step 12

11 Replace the TP sensor.

Is the action complete? — Verify repair —

12 Replace the ECM.

Is the action complete? — Verify repair —

P0122 TP Sensor Circuit Low Voltage

060RW072

Circuit Description

The throttle position (TP) sensor circuit provides a voltage

signal that changes relative to throttle blade angle. The

signal voltage will vary from below 0.6 volts at closed

throttle to about 4.5 volts at wide open throttle (WOT).

The TP signal is used by the Engine Control Module ECM

for fuel control and many of the ECM-controlled outputs.

Conditions for Setting the DTC

DIgnition SW is ON.

DThe Tp sensor voltage reading is below 100m volts.

DAbove conditions present for at least 1 second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

DThe ECM will use a default throttle position based on

mass air flow and RPM.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0122 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0122 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

locks, improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

throttle position display on the Tech 2 while moving

connectors and wiring harnesses related to the TP

sensor. A change in the display will indicate the

location of the fault.

If DTC P0122 cannot be duplicated, the information

included in the Failure Records data can be useful in

determining vehicle mileage since the DTC was last set.

DTC P0122 –TP Sensor Circuit Low Voltage

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. With the throttle closed, observe the “TP Sensor”

display on the Tech 2.

Is the “TP Sensor” below the specified value? 0.22 V Go to

Step 4

Go to

Step 3

31. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor the “Specific DTC” info for

DTC P0122.

Does the Tech 2 indicate DTC P0122 failed? —Go to

Step 4

Refer to

Diagnostic

Aids

41. Ignition “OFF.”

2. Disconnect the TP sensor electrical connector.

3. Jumper the 5 volt reference “A” circuit and the TP

signal together at the TP sensor harness connector.

4. Ignition “ON.”

Observe the “TP Sensor” display on the Tech 2.

Is the “TP Sensor” at the specified value? 5 V Go to

Step 10

Go to

Step 5

51. Disconnect jumper.

2. Connect a test light between B+ and the TP sensor

signal circuit at the TP sensor harness connector.

Observe the “TP Sensor” display on the Tech 2.

Is the “TP Sensor” at the specified value? 5 V Go to

Step 6

Go to

Step 8

61. Ignition “OFF.”

2. Disconnect the ECM and check the 5 volt reference

“A” circuit for an open or short to ground.

3. If the 5 volt reference “A” circuit is open or shorted to

ground, repair it as necessary.

Was the 5 volt reference “A” circuit open or shorted to

ground? — Verify repair Go to

Step 7

7Check the 5 volt reference “A” circuit for a poor

connection at the ECM and replace the terminal if

necessary.

Did the terminal require replacement? — Verify repair Go to

Step 12

81. Ignition “OFF.”

2. Disconnect the ECM, and check the TP signal

circuit for an open, short to ground, or short to the

sensor ground circuit.

3. If the TP sensor signal circuit is open or shorted to

ground, repair it as necessary.

Was the TP signal circuit open or shorted to ground? — Verify repair Go to

Step 9

9Check the TP sensor signal circuit for a poor

connection at the ECM and replace the terminal if

necessary.

Did the terminal require replacement? — Verify repair Go to

Step 12

Step NoYesValue(s)Action

10 Check the TP sensor signal circuit for a poor

connection at the TP sensor and replace the terminal if

necessary.

Did the terminal require replacement? — Verify repair Go to

Step 11

11 Replace the TP sensor.

Is the action complete? — Verify repair —

12 Replace the ECM.

Is the action complete? — Verify repair —

P0123 TP Sensor Circuit High Voltage

060RW077

Circuit Description

The throttle position (TP) sensor circuit provides a voltage

signal that changes relative to throttle blade angle. The

signal voltage will vary from about 0.6 volts at closed

throttle to about 4.5 volts at wide open throttle (WOT).

The TP signal is one of the most important inputs used by

the Engine Control Module ECM for fuel control and many

of the ECM-controlled outputs.

Conditions for Setting the DTC

DIgnition SW is ON.

DThe TP sensor voltage more than 4800m volts.

DAbove conditions present for at least 960m second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

DThe ECM will use a default throttle position based on

mass air flow and RPM.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0123 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0123 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

locks, improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

TP sensor display on the Tech 2 while moving

connectors and wiring harnesses related to the TP

sensor. A change in the display will indicate the

location of the fault.

DFaulty TP sensor – With the ignition key “ON,” engine

“OFF,” observe the TP sensor display on the Tech 2

while slowly depressing the accelerator to wide open

throttle. If a voltage over 4.88 volts is seen at any point

in normal accelerator travel, replace the TP sensor.

If DTC P0123 cannot be duplicated, the information

included in the Failure Records data can be useful in

determining vehicle mileage since the DTC was last set.

Test Description

Number (s) below refer to the step number(s) on the

Diagnostic Chart.

7. Components that share the TP sensor 5 volt reference

“A” circuit include the following device:

DTC P0123 – TP Sensor Circuit High Voltage

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. With the throttle closed, observe the “TP Sensor”

display on the Tech 2.

Is the “TP Sensor” above the specified value? 4.88 V Go to

Step 4

Go to

Step 3

31. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor “Specific DTC” info for DTC

P0123.

Does the Tech 2 indicate DTC P0123 failed. —Go to

Step 4

Refer to

Diagnostic

Aids

41. Disconnect the TP sensor electrical connector.

2. Observe the “TP Sensor” display on the Tech 2.

Is the “TP Sensor” near the specified value? 0 V Go to

Step 5

Go to

Step 6

5Probe the sensor ground circuit at the TP sensor

harness connector with a test light connected to B+.

Is the test light “ON?” —Go to

Step 7

Go to

Step 10

61. Ignition “OFF,” disconnect the ECM.

2. Ignition “ON,” engine “OFF.”

3. Check for a short to voltage on the TP sensor signal

circuit.

4. If the TP sensor signal circuit is shorted, repair it as

necessary.

Was the TP sensor signal circuit shorted? — Verify repair Go to

Step 12

71. Ignition “ON.”

2. Monitor the “TP Sensor” Tech 2 display while

disconnecting each of the components that share

the 5 volt reference “A” circuit (one at a time).

3. If the “TP Sensor” Tech 2 display changes, replace

the component that caused the display to change

when disconnected.

Does disconnecting any of these components cause

the “TP Sensor” display to change? — Verify repair Go to

Step 8

81. Ignition “OFF,” disconnect the ECM.

2. Ignition “ON,” engine “OFF.”

3. Check for a short to B+ on the 5 volt reference “A”

circuit.

4. If the 5 volt reference “A” circuit is shorted, repair it

as necessary.

Was the 5 volt reference “A” circuit shorted? — Verify repair Go to

Step 9

9Check for poor electrical connections at the TP sensor

and replace terminals if necessary.

Did any terminals require replacement? — Verify repair Go to

Step 11

Step NoYesValue(s)Action

10 1. Ignition “OFF.”

2. Disconnect the ECM, and check for an open sensor

ground circuit to the TP sensor.

3. If a problem is found, repair it as necessary.

W as the sensor ground circuit to the TP sensor open? —Verify repair Go to

Step 12

11 Replace the TP sensor.

Is the action complete? — Verify repair —

12 Replace the ECM.

Is the action complete? — Verify repair —

P0131 HO2S Circuit Low Voltage

060RW054

Circuit Description

The Engine Control Module ECM supplies a bias voltage

of about 450 mV between the heated oxygen sensor

(HO2S) signal high and signal low circuits. When

measured with a 10 megaohm digital voltmeter , this may

display as low as 350 mV. The oxygen sensor varies the

voltage within a range of about 1000 mV when the

exhaust is rich, down through about 10 mV when exhaust

is lean. The ECM constantly monitors the HO2S signal

during “closed loop” operation and compensates for a rich

or lean condition by decreasing or increasing injector

pulse width as necessary. If HO2S voltage remains

excessively low for an extended period of time, DTC

P0131 will be set.

Conditions for Setting the DTC

DNo related DTCs.

DVehicle is operating in “closed loop.”

DEngine coolant temperature is between 70°C and

110°C.

DThrottle angle is between 3% and 19%.

DVehicle speed is between 0Km/H and 120Km/H.

DThrottle angle voltage change reading is below 0.3m

volts.

DThe O2 sensor voltage more than 400m volts for 50

second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

D“Open loop” fuel control will be in effect.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0131 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0131 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DHeated oxygen sensor wiring – The sensor pigtail may

be routed incorrectly and contacting the exhaust

system.

DPoor ECM to engine block grounds.

DFuel pressure – The system will go lean if pressure is

too low. The ECM can compensate for some

decrease. However, If fuel pressure is too low , a DTC

P0131 may be set. Refer to

Fuel System Diagnosis

DLean injector(s) – Perform “Injector Balance Test.”

DExhaust leaks – An exhaust leak may cause outside air

to be pulled into the exhaust gas stream past the

HO2S, causing the system to appear lean. Check for

exhaust leaks that may cause a false lean condition to

be indicated.

DMAF sensor – The system can go lean if the MAF

sensor signal indicates an engine airflow

measurement that is not correct. Disconnect the MAF

sensor to see if the lean condition is corrected. If so,

replace the MAF sensor.

DFuel contamination – Water, even in small amounts,

can be delivered to the fuel injectors. The water can

cause a lean exhaust to be indicated. Excessive

alcohol in the fuel can also cause this condition. Refer

Fuel System Diagnosis

for the procedure to check

for fuel contamination.

DIf none of the above conditions are present, replace the

affected HO2S.

Test Description

Number(s) below refer to step numbers on the diagnostic

chart.

3. DTC P0131 failing during operation may indicate a

condition described in the “Diagnostic Aids” above.

If the DTC P0131 test passes while the Failure

Records conditions are being duplicated, an

intermittent condition is indicated.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P0131 –HO2S Circuit Low Voltage Bank 1 Sensor 1

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Install the Tech 2.

2. Run the engine at operating temperature.

3. Operate the vehicle within the parameters specified

under “Conditions for Setting the DTC” criteria

included in Diagnostic Support.

4. Using a Tech 2, monitor HO2S voltage.

Does the HO2S voltage remain below the specified

value? 22 mV Go to

Step 4

Go to

Step 3

31. Ignition “ON,” engine “OFF ,” review and record T ech

2 Failure Records data and note parameters.

2. Operate the vehicle within Failure Records

conditions as noted.

3. Using a Tech 2, monitor “DTC” info for DTC P0131

until the DTC P0131 test runs.

Note test result.

Does Tech 2 indicate DTC P0131 failed this ignition? —Go to

Step 4

Refer to

Diagnostic

Aids

41. Turn the ignition “OFF.”

2. Disconnect the ECM.

3. Check the HO2S high and low circuits for a short to

ground or a short to the heater ground circuit.

Are the HO2S signal circuits shorted to ground? —Go to

Step 5

Go to

Step 6

5Repair the Bank 1 HO2S 1 signal circuit.

Is the action complete? — Verify repair —

61. Turn the ignition “OFF,” HO2S and ECM

disconnected.

2. Check for continuity between the high and low

signal circuits.

Was there continuity between the high and low circuits? — Go to

Step 7

Go to

Step 8

7Repair the short between the high and low circuits.

Is the action complete? — Verify repair —

81. Ignition “OFF.”

2. Reconnect the ECM, leave the sensor

disconnected.

3. Ignition “ON.”

Does the Tech 2 indicate HO2S voltage between the

specified values? 425–475 mV

Refer to

Diagnostic

Aids

Go to

Step 9

9Replace the ECM.

Is the action complete? — Verify repair —

P0132 HO2S Circuit High Voltage

060RW054

Circuit Description

The Engine Control Module ECM supplies a bias voltage

of about 450 mV between the heated oxygen sensor

(HO2S) signal high and signal low circuits. When

measured with a 10 megaohm digital voltmeter, this may

display as low as 320 mV. The oxygen sensor varies the

voltage within a range of about 1000 mV when the

exhaust is rich, down through about 10 mV when exhaust

is lean. The ECM constantly monitors the HO2S signal

during “closed loop” operation and compensates for a rich

or lean condition by decreasing or increasing injector

pulse width as necessary. If the HO2S voltage remains

excessively high for an extended period of time, DTC

P0132 will be set.

Conditions for Setting the DTC

DNo related DTCs.

DEngine coolant temperature is between 70°C and

110°C.

D“Closed loop” commanded air/fuel ratio is between

14.5 and 14.8.

DThrottle angle is between 3% and 19%.

DVehicle speed is between 0Km/H and 120Km/H.

DThe O2 sensor voltage reading is below 600m volts for

50 second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

D“Open loop” fuel control will be in effect.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0132 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0132 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check the following items:

DFuel pressure – The system will go rich if pressure is

too high. The ECM can compensate for some

increase. However, if fuel pressure is too high, a DTC

P0132 may be set. Refer to

Fuel System Diagnosis

DPerform “Injector Balance Test” – Refer to

Fuel System

Diagnosis

DCheck the canister for fuel saturation – If full of fuel,

check canister control and hoses.

DMAF sensor –The system can go rich if MAF sensor

signal indicates an engine airflow measurement that is

not correct. Disconnect the MAF sensor to see it the

rich condition is corrected. If so, replace the MAF

sensor.

DCheck for a leak in the fuel pressure regulator

diaphragm by checking the vacuum line to the

regulator for the presence of fuel. There should be no

fuel in the vacuum line.

DAn intermittent TP sensor output will cause the system

to go rich due to a false indication of the engine

accelerating.

DShorted Heated Oxygen Sensor (HO2S) –If the HO2S

is internally shorted, the HO2S voltage displayed on

the Tech 2 will be over 1 volt. Try disconnecting the

affected HO2S with the key “ON,” engine “OFF.” If the

displayed HO2S voltage changes from over 1000 mV

to around 450 mV, replace the HO2S. Silicon

contamination of the HO2S can also cause a high

HO2S voltage to be indicated. This condition is

indicated by a powdery white deposit on the portion of

the HO2S exposed to the exhaust stream. If

contamination is noticed, replace the affected HO2S.

DOpen HO2S Signal Circuit or Faulty HO2S–A poor

connection or open in the HO2S signal circuit can

cause the DTC to set during deceleration fuel mode.

An HO2S which is faulty and not allowing a full voltage

swing between the rich and lean thresholds can also

cause this condition. Operate the vehicle by

monitoring the HO2S voltage with a Tech 2. If the

HO2S voltage is limited within a range between 300

mV to 600 mV, check the HO2S signal circuit wiring

and associated terminal conditions.

DIf none of the above conditions are present, replace the

affected HO2S.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

3. DTC P0132 failing during “deceleration fuel cutoff

mode” operation may indicate a condition described

in the “Diagnostic Aids” above. If the DTC P0132

test passes while the Failure Records conditions are

being duplicated, an intermittent condition is

indicated.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P0132 – HO2S Circuit High Voltage

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Install the Tech 2.

2. Run the engine at operating temperature.

3. Operate the vehicle within parameters specified

under “Conditions for Setting the DTC” included in

Diagnostic Support.

4. Using a Tech 2, monitor HO2S voltage.

Does the HO2S voltage remain above the specified

value?

952 mV (500

mV in

deceleration

fuel cutoff

mode) Go to

Step 4

Go to

Step 3

31. Ignition “ON,” review and record Tech 2 Failure

Records data.

2. Operate the vehicle within Failure Records

conditions as noted.

3. Using a Tech 2, monitor “DTC” info for DTC P0132

until the DTC P0132 test runs.

4. Note the test result.

Does the Tech 2 indicate DTC P0132 failed this

ignition? — Go to

Step 4

Refer to

Diagnostic

Aids

41. Ignition “OFF.”

2. Disconnect HO2S.

3. Ignition “ON.”

4. At HO2S Sensor connector (ECM side) use a DVM

to measure voltages at the high and low signal

terminals.

Are the voltages in the specified range? 3-4 V Go to

Step 5

Go to

Step 6

5Repair short to voltage in signal circuit.

Is the action complete? — Verify repair —

61. Ignition “ON,” engine“OFF.”

2. At HO2S connector (ECM side) jumper both the

HO2S high and low signal circuits (ECM side) to

ground.

3. Using a Tech 2, monitor HO2S voltage.

Is HO2S voltage below the specified value? 10 mV Go to

Step 7

Go to

Step 8

71. Disconnect the jumpers to ground from HO2S

ECM-side connector.

2. With the HO2S connector disconnected, monitor

HO2S voltage.

Is HO2S voltage between the specified values? 425-475 mV

Refer to

Diagnostic

Aids

Go to

Step 8

8Replace the ECM.

Is the action complete? — Verify repair —

P0134 HO2S Circuit Insufficient Activity

060RW054

Circuit Description

DThe Engine Control Module ECM supplies a bias

voltage of about 450 mV between the heated oxygen

sensor (HO2S) high and low circuits. When measured

with a 10 megaohm digital voltmeter, this may display

as low as 320 mV. The oxygen sensor varies the

voltage within a range of about 1000 mV when the

exhaust is rich, down through about 10 mV when

exhaust is lean. The ECM constantly monitors the

HO2S signal during “closed loop” operation and

compensates for a rich or lean condition by decreasing

or increasing injector pulse width as necessary. If the

Bank 1 HO2S 1 voltage remains at or near the 450 mV

bias for an extended period of time, DTC P0134 will be

set, indicating an open sensor signal or sensor low

circuit.

Conditions for Setting the DTC

DNo related DTCs.

DEngine run time is longer than 2 seconds.

DVehicle speed more than 60 Km/H.

DECT reading more than 70°C.

DThe O2 sensor voltage is between 350m volts and

600m volts.

DAbove conditions present for at least second.

Action Take When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

D“Open loop” fuel control will be in effect.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0134 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0134 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection or damaged harness – Inspect the

harness connectors for backed-out terminals,

improper mating, broken locks, improperly formed or

damaged terminals, poor terminal-to-wire connection,

and damaged harness.

DFaulty HO2S heater or heater circuit – With the ignition

“ON,” engine “OFF,” after a cool down period, the

HO2S 1 voltage displayed on the Tech 2 is normally

455-460 mV. A reading over 1000 mV indicates a

signal line shorted to voltage. A reading under 5 mV

indicates a signal line shorted to ground or signal lines

shorted together. Disconnect the HO2S and connect

a test light between the HO2S ignition feed and heater

ground circuits. If the test light does not light for 2

seconds when the ignition is turned on, repair the open

ignition feed or sensor ground circuit as necessary. If

the test light lights and the HO2S signal and low circuits

are OK, replace the HO2S.

DIntermittent test – With the Ignition “ON,” monitor the

HO2S signal voltage while moving the wiring harness

and related connectors. If the fault is induced, the

HO2S signal voltage will change. This may help isolate

the location of the malfunction.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

3. If the DTC P0134 test passes while the Failure

Records conditions are being duplicated, an

intermittent condition is indicated.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P0134 –HO2S Circuit Insufficient Activity

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Install the Tech 2.

2. Run the engine at operating temperature.

3. Operate the engine above 1200 RPM for two

minutes.

Does the T ech 2 indicate HO2S voltage varying outside

the specified values? 400-500 mV Go to

Step 3

Go to

Step 4

31. Ignition “ON,” engine “OFF ,” review and record T ech

2 Failure Records data and note parameters.

2. Operate the vehicle within Failure Records

conditions as noted.

3. Using a Tech 2, monitor “DTC” info for DTC P0134

until the DTC P0134 test runs.

4. Note the test result.

Does the Tech 2 indicate DTC P0134 failed this

ignition? — Go to

Step 4

Refer to

Diagnostic

Aids

4Check for a damaged harness.

Was a problem found? — Verify repair Go to

Step 5

5Check for poor HO2S high and low circuit terminal

connections at the Bank 1 HO2S 1 harness connector

and replace terminal(s) if necessary.

Did any terminals require replacement? — Verify repair Go to

Step 6

6Check for poor HO2S high and low circuit terminal

connections at the ECM and replace terminals if

necessary.

Did any terminals require replacement? — Verify repair Go to

Step 7

71. Ignition “OFF.”

2. With the ECM disconnected, check continuity of the

HO2S high circuit.

3. If the HO2S high circuit measures over 5.0 ohms,

repair open or poor connection as necessary.

Was a HO2S high circuit problem found and corrected? —Verify repair Go to

Step 8

Step NoYesValue(s)Action

81. Ignition “OFF.”

2. With the ECM disconnected, check continuity of the

HO2S low circuit.

3. If the HO2S low circuit measures over 5 ohms,

repair open or poor connection as necessary.

W as a HO2S low circuit problem found and corrected? —Verify repair Go to

Step 9

91. Ignition “ON,” engine “OFF.”

2. Disconnect HO2S and jumper the HO2S high and

low circuits (ECM side) to ground.

3. Using a Tech 2, monitor Bank 1 HO2S 1 voltage.

Is HO2S voltage in the specified range? 0-10 mV Go to

Step 10

Go to

Step 11

10 Replace HO2S.

Is the action complete? — Verify repair —

11 Replace the ECM.

Is the action complete? — Verify repair —

P0171 Fuel Trim System Too Lean

060RW054

Circuit Description

To provide the best possible combination of driveability,

fuel economy, and emission control, a “closed loop”

air/fuel metering system is used. While in “closed loop,”

the Engine Control Module ECM monitors the HO2S

signals and adjusts fuel delivery based upon the HO2S

signal voltages. A change made to fuel delivery will be

indicated by the long and short term fuel trim values which

can be monitored with a Tech 2. Ideal fuel trim values are

around 0%; if the HO2S signals are indicating a lean

condition the ECM will add fuel, resulting in fuel trim

values above 0%. If a rich condition is detected, the fuel

trim values will be below 0%, indicating that the ECM is

reducing the amount of fuel delivered. If an excessively

lean condition is detected, the ECM will set DTC P0171.

The ECM’s maximum authority to control long term fuel

trim allows a range between –15% (automatic

transmission) or –12% (manual transmission) and +20%.

The ECM monitors fuel trim under various engine

speed/load fuel trim cells before determining the status

the fuel trim diagnostic.

Conditions for Setting the DTC

DNo Tech 2 test is being run.

DEngine coolant temperature is between 35°C and

120°C.

DNo DTCs.

DIntake air temperature is below 50°C.

DBarometric pressure is more than 20 kpa.

DEngine speed more than 600 RPM.

DFuel system is in “closed loop.”

DCanister purge duty cycle is greater than 0% if on.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) after the second consecutive trip in which the

fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0171 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0171 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

Techline

locks, improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

HO2S display on the Tech 2 while moving connectors

and wiring harnesses related to the engine harness.

A change in the display will indicate the location of the

fault.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. DTCs other than P0171 may indicate a condition

present which may cause a lean condition. If this is

the case, repairing the condition which caused the

other DTC will most likely correct the DTC P0171.

4. If the DTC P0171 test passes while the Failure

Records conditions are being duplicated, the lean

condition is intermittent. Refer to

Diagnostic Aids

Symptoms

for additional information on diagnosing

intermittent problems.

DTC P0171 –Fuel Trim System Lean

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Are any DTCs set other than P0171?

—

Go to the

applicable

DTC charts

and repair the

other DTCs

before

proceeding

with this chart Go to

Step 3

31. Start the engine and operate the vehicle in “closed

loop.”

2. Observe the “Long Term Fuel Trim” display on the

Tech 2.

Is the displayed value greater than the specified value? L.T. Fuel

Trim: +20% Go to

Step 5

Go to

Step 4

41. Review and record the T ech 2 Failure Records data.

2. Clear the DTC P0171 and operate the vehicle to

duplicate the Failure Records conditions.

3. Monitor the Tech 2 “DTC” info for DTC P0171 while

operating the vehicle to duplicate the Failure

Records conditions.

4. Continue operating the vehicle until the DTC P0171

test runs and note the test result.

Does the Tech 2 indicate DTC P0171 failed this

ignition? — Go to

Step 5

The lean

condition is

not present.

If a

driveability

symptom still

exists, refer

Symptoms

section.

5Was DTC oter than DTC P0171 also set? —Go to

Step 6

Go to

Step 15

6Visually and physically inspect the vacuum hoses for

disconnects, splits, kinks, improper routing and

improper connections and repair any problem found.

Did your inspection reveal a problem requiring repair? —Verify repair Go to

Step 7

7Visually and physically inspect the crankcase

ventilation valve for proper installation and repair any

problem found (refer to

Crankcase Ventilation

System

Did your inspection reveal a problem requiring repair? — Verify repair Go to

Step 8

81. Inspect the MAF sensor inlet screen for damage or

for the presence of foreign objects which may

partially block the air flow sample through the MAF

sensor.

2. Correct any problem that is found as necessary.

Did your inspection of the MAF sensor reveal a

condition requiring repair? — Verify repair Go to

Step 9

9Start the engine and note the idle quality.

Is a high or unsteady idle being experienced? —Go to

Step 10

Go to

Step11

10 1. Visually and physically inspect the throttle body,

intake manifold for vacuum leaks.

2. Repair any vacuum leaks as necessary.

Did your inspection reveal a vacuum leak? — Verify repair Go to

Step 11

Step NoYesValue(s)Action

11 Check the fuel for excessive water, alcohol, or other

contaminants (see

Diagnosis

Engine Fuel

for the

procedure) and correct the contaminated fuel condition

if present (see

Engine Fuel

Was the fuel contaminated? — Verify repair Go to

Step 12

12 1. Visually and physically inspect the ECM injector

grounds, power grounds and sensor grounds to

ensure that they are clean, tight, and in their proper

locations.

2. If a faulty ground condition is present, correct it as

necessary.

Did your inspection reveal a condition requiring repair? —Verify repair Go to

Step 13

13 1. Disconnect the MAF sensor electrical connector.

2. Operate the vehicle in “closed loop” while

monitoring the “B1 Long Term Fuel T rim” displayed

on the Tech 2.

Does “BANK 1 S.T. FUEL TRIM” value decrease to

near the specified value? 0% Go to

Step 19

Go to

Step 14

14 Perform the procedure in the “Fuel System Pressure

Test” and repair fuel system problem if necessary.

Did Fuel System Pressure Test isolate a condition

requiring repair? — Verify repair Go to

Step 15

15 Repair any problem that is found.

Did your inspection reveal a problem? — Verify repair Go to

Step 16

16 Visually and physically inspect the Bank 1 exhaust

manifold for leaks and loose or missing hardware and

correct any problem found.

Did your inspection reveal a problem? — Verify repair Go to

Step 17

17 Perform the “Injector Balance Test,” and correct any

problem found (refer to

Fuel Metering System

Did Injector Balance Test isolate a problem? — Verify repair Go to

Step 18

18 1. Visually and physically inspect the HO2S to ensure

that it is installed securely and that the HO2S pigtail

and wiring harness are not contacting the exhaust

or otherwise damaged.

2. If a problem is found, correct it as necessary.

Did your inspection reveal a problem? — Verify repair

Refer to

Diagnostic

Aids

19 Replace the MAF sensor.

Is the action complete? — Verify repair —

P0172 Fuel Trim System Rich

060RW054

Circuit Description

To provide the best possible combination of driveability,

fuel economy, and emission control, a “closed loop”

air/fuel metering system is used. While in “closed loop,”

the Engine Control Module ECM monitors the heated

oxygen sensors (HO2S) signals and adjusts fuel delivery

based upon the HO2S signal voltages. A change made to

fuel delivery will be indicated by the long and short term

fuel trim values which can be monitored with a Tech 2.

Ideal fuel trim values are around 0%; if the HO2S signals

are indicating a lean condition the ECM will add fuel,

resulting in fuel trim values above 0%. If a rich condition is

detected, the fuel trim values will be below 0%, indicating

that the ECM is reducing the amount of fuel delivered. If

an excessively rich condition is detected on Bank 1, the

ECM will set DTC P0172.

The ECM’s maximum authority to control long term fuel

trim allows a range between –15% (automatic

transmission) or –12 (manual transmission) and +20%.

The ECM’s maximum authority to control short term fuel

trim allows a range between –11% and +20%. The ECM

monitors fuel trim under various engine speed/load fuel

trim cells before determining the status of the fuel trim

diagnostic.

Conditions for Setting the DTC

DNo Tech 2 test is being run.

DNone of the following was set: HO2S DTCs, (response,

transition, open, low volts, no activity), MAF DTCs,

TPS DTCs, BARO DTCs, IAT DTCs, canister purge

DTCs, injector circuit DTCs.

DEngine coolant temperature is between 35°C and

120°C.

DIntake air temperature is below 50°C.

DBarometric pressure is more than 20 kpa.

DEngine speed more than 600 RPM.

DFuel system is in “closed loop.”

DCanister purge duty cycle is greater than 0% if on.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) after the second consecutive trip in which the

fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0172 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0172 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect harness connectors

for backed-out terminals, improper mating, broken

locks, improperly formed or damaged terminals, and

poor terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

HO2S display on the Tech 2 while moving connectors

and wiring harnesses related to the engine harness.

A change in the display will indicate the location of the

fault.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. DTCs other than P0172 may indicate a condition

present which may cause a lean condition. If this is

the case, repairing the condition which caused the

other DTC will most likely correct the DTC P0172.

4. If the DTC P0172 test passes while the Failure

Records conditions are being duplicated, the rich

condition is intermittent. Refer to

Diagnostic Aids

Symptoms

for additional information on diagnosing

intermittent problems.

DTC P0172 – Fuel Trim System Rich

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Are any DTCs set other than P0172?

—

Go to the

applicable

DTC charts

and repair the

other DTCs

before

proceeding

with this chart Go to

Step 3

31. Start the engine and operate the vehicle in “closed

loop.”

2. Observe “B1 Long Term Fuel Trim” display on the

Tech 2.

Is the displayed value more negative than the specified

value?

L.T. Fuel

Trim: –15%

(auto. trans.)

OR –12%

(man. trans.) Go to

Step 5

Go to

Step 4

41. Review and record the T ech 2 Failure Records data.

2. Clear the DTC P0172 and operate the vehicle to

duplicate the Failure Records conditions.

3. Monitor the Tech 2 “Specific DTC” info for DTC

P0172 while operating the vehicle to duplicate the

Failure Records conditions.

4. Continue operating the vehicle until the DTC P0172

test runs and note test result.

Does the Tech 2 indicate DTC P0172 failed this

ignition? — Go to

Step 5

The rich

condition is

not present.

If a

driveability

symptom still

exists, refer

Symptoms

5Is DTC also set? —Go to

Step 6

Go to

Step 15

6Visually and physically inspect the air filter element and

replace it if necessary.

Did the air filter require replacement? — Verify repair Go to

Step 7

7Visually and physically inspect the air intake duct for

collapse or restriction and repair if necessary.

Did your inspection reveal a condition requiring repair? —Verify repair Go to

Step 8

Step NoYesValue(s)Action

8Inspect the MAF sensor inlet screen for damage or for

the presence of foreign objects which may partially

block air flow through the screen and correct any

problem found.

Did your inspection of the MAF sensor reveal a

condition requiring repair or replacement? — Verify repair Go to

Step 9

9Start the engine and note the idle quality.

Is a low or unsteady idle being experienced? —Go to

Step 10

Go to

Step 11

10 1. Ignition “OFF.”

2. Physically inspect the throttle body bore, throttle

plate, and IAC passages for coking and foreign

objects.

3. If a problem was found, repair as necessary.

Did your inspection reveal a condition requiring repair? —Verify repair Go to

Step 11

11 1. Disconnect the vacuum hose from the fuel pressure

regulator and inspect the hose for the presence of

fuel.

2. If fuel is present in the vacuum hose, replace the

fuel pressure regulator (refer to

Fuel Metering

System

Did the fuel pressure regulator require replacement? — Verify repair Go to

Step 12

12 Ignition “ON,” engine “OFF,” monitor the TP Angle

display on the Tech 2 while slowly depressing the

accelerator pedal.

Does the TP Angle display increase steadily and

evenly from minimum value at closed throttle to

maximum value at wide–open throttle?

Minimum 0%

Maximum

100% Go to

Step 13

Go to

Step 21

13 1. Disconnect the MAF sensor electrical connector.

2. Operate the vehicle in “closed loop” while

monitoring the “Long Term Fuel Trim” and “Short

Term Fuel Trim” display on the Tech 2.

Did both values change to near the specified value? 0% Go to

Step 22

Go to

Step 14

14 1. Perform “Fuel System Pressure Test.”

2. If Fuel System Pressure Test isolates a problem,

repair as necessary (refer to

Engine Fuel

Fuel

Metering System

Did the Fuel System Pressure Test isolate a problem

requiring repair? — Verify repair Go to

Step 15

15 1. Ignition “ON,” engine “OFF.”

2. Connect a test light between the harness connector

terminals of canister purge solenoid.

Is the test light on? —Go to

Step 16

Go to

Step 19

16 Check for short to ground in the wire (red/blue)

between the canister purge solenoid and ECM terminal

A-15.

Was there a short to ground? —Go to

Step 17

Go to

Step 18

17 Repair the short to ground.

Is the action complete? — Verify repair —

StepNoYesValue(s)Action

18 Replace the ECM.

IMPORTANT:The replacement ECM must be

programmed. Refer to

On-Vehicle Service

Engine

Control Module and Sensors

for procedures.

Is the action complete? — Verify repair —

19 1. Perform the “Injector Balance Test.”

2. If Injector Balance T est isolates a problem, repair as

necessary (refer to

Fuel Metering System

Did the Injector Balance Test isolate a problem

requiring repair? — Verify repair Go to

Step 20

20 1. Remove and visually/physically inspect the HO2S

for silicon contamination. This will be indicated by a

powdery white deposit on the portion of the HO2S

that is exposed to the exhaust stream.

2. If contamination is evident on the Bank 1 HO2S 1,

replace the contaminated sensors.

Did the sensor require replacement? — Verify repair

Refer to

Diagnostic

Aids

21 1. Check the TP sensor mounting screws and tighten

or replace them as necessary if they are loose or

missing.

2. If the screws are OK, replace the TP sensor.

Is the action complete? — Verify repair —

22 Replace the MAF sensor.

Is the action complete? — Verify repair —

P0201 Injector 1 Control Circuit

060RW055

Circuit Description

The Engine Control Module ECM has six individual

injector driver circuits. Each controls an injector . When a

driver circuit is grounded by the ECM, the injector is

activated. The ECM monitors the current in each driver

circuit. The voltage on each driver is monitored to detect

a fault. If the voltage is not what the ECM expects to

monitor on the circuit, a DTC is set. This DTC is also set if

an injector driver is shorted to voltage or if there is an open

circuit.

Conditions for Setting the DTC

DThe battery voltage is more than 11 volts.

DInjector pulse reading is between 2.5m second and

7.5m second.

DNo fuel cut.

DEngine running speed is between 700 r.p.m and 2000

r.p.m.

DNo related CKP/CMP DTCs.

DNo injector pulse reading with engine running speed is

200 r.p.m.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn “OFF” the MIL on the third

consecutive trip cycle in which the diagnostic has been

run and the fault is no longer present.

DA history DTC P0201 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0201 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

An injector driver circuit that is open or shorted to voltage

will cause a DTC P0201 to set. It will also cause a misfire

due to an inoperative injector. A misfire DTC will also be

set indicating which cylinder is inoperative.

Long term and short term fuel trims that are excessively

high or low are a good indication that an injector is faulty.

Use Fuel Injector Coil Test Procedure to check for faulty

injectors.

Test Description

The number(s) below refer to the step number(s) on the

Diagnostic Chart.

3. This step determines if DTC P0201 is the result of a

hard failure or an intermittent condition.

5. A special injector test connector is provided so that

the injectors can be electrically tested without

removal of the manifold. The special 7-way gray

connector is located at the rear of the air cleaner

assembly. The test connector can be identified by

the blue connector lock which is tethered to the

wiring harness. If the light for cylinder 1 is “ON”

steady before cranking the engine as well as while

cranking the engine, then the injector driver circuit is

shorted to ground.

If the test light blinks while cranking, the ECM and

the wiring to the injectors are OK. The Fuel Injector

Coil Test Procedure will check if the injectors are

faulty.R321054

7. Because the test light was “ON” steady, voltage to

the injector is OK, but the driver circuit is grounded

at all times. This step determines if the circuit is

shorted to ground or the ECM is faulty.

9.The reading should be about 12-14W.

10.Locating the open in the harness or in the injector

will require removal of the manifold to provide

access.

DTC P0201 – Injector 1 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Will the engine start?

—Go to

Step 3

Go to

Engine

Cranks But

Will Not Run

chart

31. Install the Tech 2. Clear the DTC.

2. Idle the engine for one minute.

Does DTC P0201 reset? —Go to

Step 5

Go to

Step 4

41. Review the Freeze Frame data with the ignition

“ON” and the engine “OFF” and note the

parameters.

2. Operate the vehicle within the Freeze Frame

conditions as noted.

Does P0201 reset? —Go to

Step 5

Go to

Diagnostic

Aids

51. Engine “OFF.”

2. Disconnect the injector connector.

3. Install an injector test light 5-8840-2636-0 on the

injector test connector.

4. Crank the engine and note the light.

Does the injector test light blink? —

Go to

Fuel

Injector Coil

Test

Procedure

Go to

Step 6

Step NoYesValue(s)Action

6Note whether the injector test light for cylinder 1 was

“OFF” or “ON” steady in step 5.

Was the test light “ON” steady while cranking the

engine? — Go to

Step 7

Go to

Step 9

71. Disconnect the ECM connector for the affected

injectors.

2. With a test light connected to B+, probe the affected

injector driver circuit.

Does the test light illuminate? —Go to

Step 8

Go to

Step 15

8Repair short to ground in the injector driver circuit.

Is the action complete? —

Go to

OBD

System

Check

—

91. Disconnect the injector test connector.

2. At the injector side of the harness, connect an

ohmmeter between the positive wire (red with blue

tracer) and the wire for cylinder 1 (green with white

tracer).

Does the ohmmeter indicate continuity? —Go to

Step 11

Go to

Step 10

10 Repair the open injector harness wire or open injector .

Is the action complete? — Verify repair —

11 At the ECM side of the injector test connector, check

the green/white wire for a short to voltage.

Was there a short to voltage? —Go to

Step 12

Go to

Step 13

12 Repair the short to voltage.

Is the action complete? — Verify repair —

13 Check for an open circuit between the injector test

connector and the ECM.

Was there an open circuit? —Go to

Step 14

Go to

Step 15

14 Repair the open circuit.

Is the action complete? — Verify repair —

15 Replace the ECM.

Is the action complete? — Verify repair —

P0202 Injector 2 Control Circuit

060RW055

Circuit Description

The Engine Control Module ECM has six individual

injector driver circuits. Each controls an injector . When a

driver circuit is grounded by the ECM, the injector is

activated. The ECM monitors the current in each driver

circuit. The voltage on each driver is monitored to detect

a fault. If the voltage is not what the ECM expects to

monitor on the circuit, a DTC is set. This DTC is also set if

an injector driver is shorted to voltage or if there is an open

circuit.

Conditions for Setting the DTC

DThe battery voltage is more than 11 volts.

DInjector pulse reading is between 2.5m second and

7.5m second.

DNo fuel cut.

DEngine running speed is between 700 r.p.m and 2000

r.p.m.

DNo related CKP/CMP DTCs.

DNo injector pulse reading with engine running speed is

200 r.p.m.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn “OFF” the MIL on the third

consecutive trip cycle in which the diagnostic has been

run and the fault is no longer present.

DA history DTC P0202 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0202 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

An injector driver circuit that is open or shorted to voltage

will cause a DTC P0202 to set. It will also cause a misfire

due to an inoperative injector. A misfire DTC will also be

set indicating which cylinder is inoperative.

Long term and short term fuel trims that are excessively

high or low are a good indication that an injector is faulty.

Use Fuel Injector Coil Test Procedure to check for faulty

injectors.

Test Description

The number(s) below refer to the step number(s) on the

Diagnostic Chart.

3. This step determines if DTC P0202 is the result of a

hard failure or an intermittent condition.

5. A special injector test connector is provided so that

the injectors can be electrically tested without

removal of the manifold. The special 7-way gray

connector is located at the rear of the air cleaner

assembly. The test connector can be identified by

the blue connector lock which is tethered to the

wiring harness. If the light for cylinder 2 is “ON”

steady before cranking the engine as well as while

cranking the engine, then the injector driver circuit is

shorted to ground.

If the test light blinks while cranking, the ECM and

the wiring to the injectors are OK. Fuel Injector Coil

Test Procedure will check if the injectors are faulty.

R321055

7. Because the test light was “ON” steady, voltage to

the injector is OK, but the driver circuit is grounded

at all times. This step determines if the circuit is

shorted to ground or the ECM is faulty.

9.The reading should be about 12-14W.

10.Locating the open in the harness or in the injector

will require removal of the manifold to provide

access.

DTC P0202 – Injector 2 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Will the engine start?

—Go to

Step 3

Go to

Engine

Cranks But

Will Not Run

chart

31. Install the Tech 2. Clear the DTC.

2. Idle the engine for one minute.

Does DTC P0202 reset? —Go to

Step 5

Go to

Step 4

41. Review the Freeze Frame data with the ignition

“ON” and the engine “OFF” and note the

parameters.

2. Operate the vehicle within the Freeze Frame

conditions as noted.

Does P0202 reset? —Go to

Step 5

Go to

Diagnostic

Aids

51. Engine “OFF.”

2. Disconnect the injector test connector.

3. Install an injector test light 5-8840-2636-0 on

injector test connector

4. Crank the engine and note the light.

Does the cylinder 2 test light blink? —

Go to

Fuel

Injector Coil

Test

Procedure

Go to

Step 6

Step NoYesValue(s)Action

6Note whether the injector test light for cylinder 2 was

“OFF” or “ON” steady in step 5.

Was the test light “ON” steady while cranking the

engine? — Go to

Step 7

Go to

Step 9

71. Disconnect the ECM connector for the affected

injectors.

2. With a test light connected to B+, probe the affected

injector driver circuit.

Does the test light illuminate? —Go to

Step 8

Go to

Step 15

8Repair short to ground in the injector driver circuit.

Is the action complete? —

Go to

OBD

System

Check

—

91. Disconnect the injector test connector.

2. At the injector side of the harness, connect an

ohmmeter between the positive wire (red with blue

tracer) and the wire for cylinder 2 (green with orange

tracer).

Does the ohmmeter indicate continuity? —Go to

Step 11

Go to

Step 10

10 Repair the open injector harness wire or open injector .

Is the action complete? — Verify repair —

11 At the ECM side of the injector test connector, check

the green/orange wire for a short to voltage.

Was there a short to voltage? —Go to

Step 12

Go to

Step 13

12 Repair the short to voltage.

Is the action complete? — Verify repair —

13 Check for an open circuit between the injector test

connector and the ECM.

Was there an open circuit? —Go to

Step 14

Go to

Step 15

14 Repair the open circuit.

Is the action complete? — Verify repair —

15 Replace the ECM.

Is the action complete? — Verify repair —

P0203 Injector 3 Control Circuit

060RW055

Circuit Description

The Engine Control Module ECM has six individual

injector driver circuits. Each controls an injector. When

the driver circuit is grounded by the ECM, the injector is

activated. The ECM monitors the current in each driver

circuit. The voltage on each driver is monitored to detect

a fault. If the voltage is not what the ECM expects to

monitor on the circuit, a DTC is set. This DTC is also set if

an injector driver is shorted to voltage or if there is an open

circuit.

Conditions for Setting the DTC

DThe battery voltage is more than 11 volts.

DInjector pulse reading is between 2.5m second and

7.5m second.

DNo fuel cut.

DEngine running speed is between 700 r.p.m and 2000

r.p.m.

DNo related CKP/CMP DTCs.

DNo injector pulse reading with engine running speed is

200 r.p.m.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn “OFF” the MIL on the third

consecutive trip cycle in which the diagnostic has been

run and the fault is no longer present.

DA history DTC P0203 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0203 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

An injector driver circuit that is open or shorted to voltage

will cause a DTC P0203 to set. It will also cause a misfire

due to an inoperative injector. A misfire DTC will also be

set indicating which cylinder is inoperative.

Long term and short term fuel trims that are excessively

high or low are a good indication that an injector is faulty.

Use Fuel Injector Coil Test Procedure to check for faulty

injectors.

Test Description

The number(s) below refer to the step number(s) on the

Diagnostic Chart.

3. This step determines if DTC P0203 is the result of a

hard failure or an intermittent condition.

5. A special injector test connector is provided so that

the injectors can be electrically tested without

removal of the manifold. The special 7-way gray

connector is located at the rear of the air cleaner

assembly. The test connector can be identified by

the blue connector lock which is tethered to the

wiring harness. If the light for cylinder 3 is “ON”

steady before cranking the engine as well as while

cranking the engine, then the injector driver circuit is

shorted to ground.

If the test light blinks while cranking, the ECM and

the wiring to the injectors are OK. The Fuel Injector

Coil Test Procedure will check if the injectors are

faulty.R321056

7. Because the test light was “ON” steady, voltage to

the injector is OK, but the driver circuit is grounded

at all times. This step determines if the circuit is

shorted to ground or the ECM is faulty.

9.The reading should be about 12-14W.

10.Locating the open in the harness or in the injector

will require removal of the manifold to provide

access.

DTC P0203 – Injector 3 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Will the engine start?

—Go to

Step 3

Go to

Engine

Cranks But

Will Not Run

chart

31. Install the Tech 2. Clear the DTC.

2. Idle the engine for one minute.

Does DTC P0203 reset? —Go to

Step 5

Go to

Step 4

41. Review the Freeze Frame data with the ignition

“ON” and the engine “OFF” and note the

parameters.

2. Operate the vehicle within the Freeze Frame

conditions as noted.

Does P0203 reset? —Go to

Step 5

Go to

Diagnostic

Aids

51. Engine “OFF.”

2. Disconnect the injector test connector .

3. Install an injector test light 5-8840-2636-0 on

injector connector

4. Crank the engine and note the light.

Does the cylinder 3 test light blink? —

Go to

Fuel

Injector Coil

Test

Procedure

Go to

Step 6

Step NoYesValue(s)Action

6Note whether the injector test light for cylinder 3 was

“OFF” or “ON” steady in step 5.

Was the test light “ON” steady while cranking the

engine? — Go to

Step 7

Go to

Step 9

71. Disconnect the ECM connector for the affected

injectors.

2. With a test light connected to B+, probe the affected

injector driver circuit.

Does the test light illuminate? —Go to

Step 8

Go to

Step 15

8Repair short to ground in the injector driver circuit.

Is the action complete? —

Go to

OBD

System

Check

—

91. Disconnect the injector test connector.

2. At the injector side of the harness, connect an

ohmmeter between the positive wire (red with blue

tracer) and the wire for cylinder 3 (green).

Does the ohmmeter indicate continuity? —Go to

Step 11

Go to

Step 10

10 Repair the open injector harness wire or open injector .

Is the action complete? — Verify repair —

11 At the ECM side of the injector test connector, check

the green wire for a short to voltage.

Was there a short to voltage? —Go to

Step 12

Go to

Step 13

12 Repair the short to voltage.

Is the action complete? — Verify repair —

13 Check for an open circuit between the injector test

connector and the ECM.

Was there an open circuit? —Go to

Step 14

Go to

Step 15

14 Repair the open circuit.

Is the action complete? — Verify repair —

15 Replace the ECM.

Is the action complete? — Verify repair —

P0204 Injector 4 Control Circuit

060RW055

Circuit Description

The Engine Control Module ECM has six individual

injector driver circuits. Each controls an injector. When

the driver circuit is grounded by the ECM, the injector is

activated. The ECM monitors the current in each driver

circuit. The voltage on each driver is monitored to detect

a fault. If the voltage is not what the ECM expects to

monitor on the circuit, a DTC is set. This DTC is also set if

an injector driver is shorted to voltage or if there is an open

circuit.

Conditions for Setting the DTC

DThe battery voltage is more than 11 volts.

DInjector pulse reading is between 2.5m second and

7.5m second.

DNo fuel cut.

DEngine running speed is between 700 r.p.m and 2000

r.p.m.

DNo related CKP CMP/DTCs.

DNo injector pulse reading with engine running speed is

200 r.p.m.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn “OFF” the MIL on the third

consecutive trip cycle in which the diagnostic has been

run and the fault is no longer present.

DA history DTC P0204 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0204 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

An injector driver circuit that is open or shorted to voltage

will cause a DTC P0204 to set. It will also cause a misfire

due to an inoperative injector. A misfire DTC will also be

set indicating which cylinder is inoperative.

Long term and short term fuel trims that are excessively

high or low are a good indication that an injector is faulty.

Use Fuel Injector Coil Test Procedure to check for faulty

injectors.

Test Description

The number(s) below refer to the step number(s) on the

Diagnostic Chart.

3. This step determines if DTC P0204 is the result of a

hard failure or an intermittent condition.

5. A special injector test connector is provided so that

the injectors can be electrically tested without

removal of the manifold. The special 7-way gray

connector is located at the rear of the air cleaner

assembly. The test connector can be identified by

the blue connector lock which is tethered to the

wiring harness. If the light for cylinder 4 is “ON”

steady before cranking the engine as well as while

cranking the engine, then the injector driver circuit is

shorted to ground.

If the test light blinks while cranking, the ECM and

the wiring to the injectors are OK. The Fuel Injector

Coil Test Procedure will check if the injectors are

faulty.R321057

7. Because the test light was “ON” steady, voltage to

the injector is OK, but the driver circuit is grounded

at all times. This step determines if the circuit is

shorted to ground or the ECM is faulty.

9.The reading should be about 12-14W.

10.Locating the open in the harness or in the injector

will require removal of the manifold to provide

access.

DTC P0204 – Injector 4 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Will the engine start?

—Go to

Step 3

Go to

Engine

Cranks But

Will Not Run

chart

31. Install the Tech 2. Clear the DTC.

2. Idle the engine for one minute.

Does DTC P0204 reset? —Go to

Step 5

Go to

Step 4

41. Review the Freeze Frame data with the ignition

“ON” and the engine “OFF” and note the

parameters.

2. Operate the vehicle within the Freeze Frame

conditions as noted.

Does P0204 reset? —Go to

Step 5

Go to

Diagnostic

Aids

51. Engine “OFF.”

2. Disconnect the injector test connector.

3. Install an injector test light 5-8840-2636-0 on

injector test connector.

4. Crank the engine and note the light.

Does the cylinder 4 test light blink? —

Go to

Fuel

Injector Coil

Test

Procedure

Go to Step 6

Step NoYesValue(s)Action

6Note whether the injector test light was “OFF” or “ON”

steady in step 5.

Was the test light “ON” steady while cranking the

engine? — Go to

Step 7

Go to

Step 9

71. Disconnect the ECM connector for the affected

injectors.

2. With a test light connected to B+, probe the affected

injector driver circuit.

Does the test light illuminate? —Go to

Step 8

Go to

Step 15

8Repair short to ground in the injector driver circuit.

Is the action complete? —

Go to

OBD

System

Check

—

91. Disconnect the injector test connector.

2. At the injector side of the harness, connect an

ohmmeter between the positive wire (red with blue

tracer) and the wire for cylinder 4 (green/red).

Does the ohmmeter indicate continuity? —Go to

Step 11

Go to

Step 10

10 Repair the open injector harness wire or open injector .

Is the action complete? — Verify repair —

11 At the ECM side of the injector test connector, check

the green/red wire for a short to voltage.

Was there a short to voltage? —Go to

Step 12

Go to

Step 13

12 Repair the short to voltage.

Is the action complete? — Verify repair —

13 Check for an open circuit between the injector test

connector and the ECM.

Was there an open circuit? —Go to

Step 14

Go to

Step 15

14 Repair the open circuit.

Is the action complete? — Verify repair —

15 Replace the ECM.

Is the action complete? — Verify repair —

P0205 Injector 5 Control Circuit

060RW055

Circuit Description

The Engine Control Module ECM has six individual

injector driver circuits. Each controls an injector. When

the driver circuit is grounded by the ECM, the injector is

activated. The ECM monitors the current in each driver

circuit. The voltage on each driver is monitored to detect a

fault. If the voltage is not what the ECM expects to

monitor on the circuit, a DTC is set. This DTC is also set if

an injector driver is shorted to voltage or if there is an open

circuit.

Conditions for Setting the DTC

DThe battery voltage is more than 11 volts.

DInjector pulse reading is between 2.5m second and

7.5m second.

DNo fuel cut.

DEngine running speed is between 700 r.p.m and 2000

r.p.m.

DNo related CKP/CMP DTCs.

DNo injector pulse reading with engine running speed is

200 r.p.m.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn “OFF” the MIL on the third

consecutive trip cycle in which the diagnostic has been

run and the fault is no longer present.

DA history DTC P0205 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0205 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

An injector driver circuit that is open or shorted to voltage

will cause a DTC P0205 to set. It will also cause a misfire

due to an inoperative injector. A misfire DTC will also be

set indicating which cylinder is inoperative.

Long term and short term fuel trims that are excessively

high or low are a good indication that an injector is faulty.

Use Fuel Injector Coil Test Procedure to check for faulty

injectors.

Test Description

The number(s) below refer to the step number(s) on the

Diagnostic Chart.

3. This step determines if DTC P0205 is the result of a

hard failure or an intermittent condition.

5. A special injector test connector is provided so that

the injectors can be electrically tested without

removal of the manifold. The special 7-way gray

connector is located at the rear of the air cleaner

assembly. The test connector can be identified by

the blue connector lock which is tethered to the

wiring harness. If the light for cylinder 5 is “ON”

steady before cranking the engine as well as while

cranking the engine, then the injector driver circuit is

shorted to ground.

If the test light blinks while cranking, the ECM and

the wiring to the injectors are OK. Fuel Injector Coil

Test Procedure will check if the injectors are faulty.

R321058

7. Because the test light was “ON” steady, voltage to

the injector is OK, but the driver circuit is grounded

at all times. This step determines if the circuit is

shorted to ground or the ECM is faulty.

9.The reading should be about 12-14W.

10.Locating the open in the harness or in the injector

will require removal of the manifold to provide

access.

DTC P0205 – Injector 5 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Will the engine start?

—Go to

Step 3

Go to

Engine

Cranks But

Will Not Run

chart

31. Install the Tech 2. Clear the DTC.

2. Idle the engine for one minute.

Does DTC P0205 reset? —Go to

Step 5

Go to

Step 4

41. Review the Freeze Frame data with the ignition

“ON” and the engine “OFF” and note the

parameters.

2. Operate the vehicle within the Freeze Frame

conditions as noted.

Does P0205 reset? —Go to

Step 5

Go to

Diagnostic

Aids

51. Engine “OFF.”

2. Disconnect the injector test connector.

3. Install an injector test light 5-8840-2636-0 on the

injector test connector.

4. Crank the engine and note the light.

Does the cylinder 5 test light blink? —

Go to

Fuel

Injector Coil

Test

Procedure

Go to

Step 6

Step NoYesValue(s)Action

6 Note whether the injector test light was “OFF” or “ON”

steady in step 5.

Was the test light “ON” steady while cranking the

engine? — Go to

Step 7

Go to

Step 9

71. Disconnect the ECM connector for the affected

injectors.

2. With a test light connected to B+, probe the affected

injector driver circuit.

Does the test light illuminate? —Go to

Step 8

Go to

Step 15

8Repair short to ground in the injector driver circuit.

Is the action complete? —

Go to

OBD

System

Check

—

91. Disconnect the injector test connector.

2. At the injector side of the harness, connect an

ohmmeter between the positive wire (red with blue

tracer) and the wire for cylinder 5 (green with black

tracer).

Does the ohmmeter indicate continuity? —Go to

Step 11

Go to

Step 10

10 Repair the open injector harness wire or open injector .

Is the action complete? — Verify repair —

11 At the ECM side of the injector test connector, check

the green/black wire for a short to voltage.

Was there a short to voltage? —Go to

Step 12

Go to

Step 13

12 Repair the short to voltage.

Is the action complete? — Verify repair —

13 Check for an open circuit between the injector test

connector and the ECM.

Was there an open circuit? —Go to

Step 14

Go to

Step 15

14 Repair the open circuit.

Is the action complete? — Verify repair —

15 Replace the ECM.

Is the action complete? — Verify repair —

P0206 Injector 6 Control Circuit

060RW055

Circuit Description

The Engine Control Module ECM has six individual

injector driver circuits. Each controls an injector. When

the driver circuit is grounded by the ECM, the injector is

activated. The ECM monitors the current in each driver

circuit. The voltage on each driver is monitored to detect

a fault. If the voltage is not what the ECM expects to

monitor on the circuit, a DTC is set. This DTC is also set if

an injector driver is shorted to voltage or if there is an open

circuit.

Conditions for Setting the DTC

DThe battery voltage is more than 11 volts.

DInjector pulse reading is between 2.5m second and

7.5m second.

DNo fuel cut.

DEngine running speed is between 700 r.p.m and 2000

r.p.m.

DNo related CKP CMP DTCs.

DNo injector pulse reading with engine running speed is

200 r.p.m.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn “OFF” the MIL on the third

consecutive trip cycle in which the diagnostic has been

run and the fault is no longer present.

DA history DTC P0206 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0206 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

An injector driver circuit that is open or shorted to voltage

will cause a DTC P0206 to set. It will also cause a misfire

due to an inoperative injector. A misfire DTC will also be

set indicating which cylinder is inoperative.

Long term and short term fuel trims that are excessively

high or low are a good indication that an injector is faulty.

Use Fuel Injector Coil Test Procedure to check for faulty

injectors.

Test Description

The number(s) below refer to the step number(s) on the

Diagnostic Chart.

3. This step determines if DTC P0206 is the result of a

hard failure or an intermittent condition.

5. A special injector test connector is provided so that

the injectors can be electrically tested without

removal of the manifold. The special 7-way gray

connector is located at the rear of the air cleaner

assembly. The test connector can be identified by

the blue connector lock which is tethered to the

wiring harness. If the light for cylinder 6 is “ON”

steady before cranking the engine as well as while

cranking the engine, then the injector driver circuit is

shorted to ground.

If the test light blinks while cranking, the ECM and

the wiring to the injectors are OK. The Fuel Injector

Coil Test Procedure will check if the injectors are

faulty.R321059

7. Because the test light was “ON” steady, voltage to

the injector is OK, but the driver circuit is grounded

at all times. This step determines if the circuit is

shorted to ground or the ECM is faulty.

9.The reading should be about 12-14W.

10.Locating the open in the harness or in the injector

will require removal of the manifold to provide

access.

DTC P0206 – Injector 6 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Will the engine start?

—Go to

Step 3

Go to

Engine

Cranks But

Will Not Run

chart

31. Install the Tech 2. Clear the DTC.

2. Idle the engine for one minute.

Does DTC P0206 reset? —Go to

Step 5

Go to

Step 4

41. Review the Freeze Frame data with the ignition

“ON” and the engine “OFF” and note the

parameters.

2. Operate the vehicle within the Freeze Frame

conditions as noted.

Does P0206 reset? —Go to

Step 5

Go to

Diagnostic

Aids

51. Engine “OFF.”

2. Disconnect the injector test connector.

3. Install an injector test light 5-8840-2636-0 on

injector test connector.

4. Crank the engine and note the light.

Does the cylinder 6 test light blink? —

Go to

Fuel

Injector Coil

Test

Procedure

Go to

Step 6

Step NoYesValue(s)Action

6Note whether the injector test light was “OFF” or “ON”

steady in step 5.

Was the test light “ON” steady while cranking the

engine? — Go to

Step 7

Go to

Step 9

71. Disconnect the ECM connector for the affected

injectors.

2. With a test light connected to B+, probe the affected

injector driver circuit.

Does the test light illuminate? —Go to

Step 8

Go to

Step 15

8Repair short to ground in the injector driver circuit.

Is the action complete? —

Go to

OBD

System

Check

—

91. Disconnect the injector test connector.

2. At the injector side of the harness, connect an

ohmmeter between the positive wire (red with blue

tracer) and the wire for cylinder 6 (green with yellow

tracer).

Does the ohmmeter indicate continuity? —Go to

Step 11

Go to

Step 10

10 Repair the open injector harness wire or open injector

Is the action complete? — Verify repair —

11 At the ECM side of the injector test connector, check

the green/yellow wire for a short to voltage.

Was there a short to voltage? —Go to

Step 12

Go to

Step 13

12 Repair the short to voltage.

Is the action complete? — Verify repair —

13 Check for an open circuit between the injector test

connector and the ECM.

Was there an open circuit? —Go to

Step 14

Go to

Step 15

14 Repair the open circuit.

Is the action complete? — Verify repair —

15 Replace the ECM.

Is the action complete? — Verify repair —

P0336 CKP Reference Signal Circuit

060RW072

Circuit Description

The CKP reference signal is produced by the crankshaft

position (CKP) sensor . During one crankshaft revolution,

crankshaft pulses will be produced. The Engine Control

Module ECM uses the CKP reference signal to calculate

engine RPM and crankshaft position. The ECM

constantly monitors the number of pulses on the CKP

reference circuit and compares them to the number of

camshaft position (CMP) signal pulses being received. If

the ECM receives an incorrect number of pulses on the

CKP reference circuit, DTC P0336 will set.

Conditions for Setting the DTC

DIgnition SW is ON.

DExtra or missing pulse is detected between

consecutive CKP reference pulses.

DThe battery voltage is more than 11 volts.

DEngine running speed is below 2000 r.p.m.

DThe CKP Pulse reading is 110 for 10th.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) after the second consecutive trip in which the

fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0336 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0336 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

An intermittent may be caused by a poor connection,

rubbed–through wire insulation or a wire broken inside the

insulation. Check for:

DPoor connection – Inspect the ECM harness and

connectors for improper mating, broken locks,

improperly formed or damaged terminals, and poor

terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, disconnect

the ECM, turn the ignition on and observe a voltmeter

connected to the CKP reference circuit at the ECM

harness connector while moving connectors and

wiring harnesses related to the ICM. A change in

voltage will indicate the location of the fault.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P0336 – 58X Reference Signal Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Attempt to start the engine.

Does the engine start? —Go to

Step 3

Go to

“Engine

Cranks But

Will Not Run”

chart

31. Review and record Failure Records information.

2. Clear DTC P0336.

3. Start the engine and idle for 1 minute.

4. Observe DTCs.

Is DTC P0336 set? —Go to

Step 4

Refer to

Diagnostic

Aids

41. Disconnect the ECM and CKP sensor.

2. Check for an open or a short to ground in the CKP

reference circuit between the CKP sensor

connector and the ECM harness connector.

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 5

51. Reconnect the ECM and CKP sensor.

2. Connect a DVM to measure voltage on the CKP

reference circuit at the ECM connector.

3. Observe the voltage while cranking the engine.

Is the voltage near the specified value? 2.5 V Go to

Step 8

Go to

Step 6

6Check the connections at the CKP sensor and replace

the terminals if necessary.

Did any terminals require replacement? — Verify repair Go to

Step 7

7Replace the CKP sensor . Use caution to avoid any hot

oil that may drip out.

Is the action complete? — Verify repair —

8Check connections at the ECM and replace the

terminals if necessary.

Did any terminals require replacement? — Verify repair Go to

Step 10

9Replace the ECM.

Is the action complete? — Verify repair —

P0337 CKP Sensor Circuit Low Frequency

060RW072

Circuit Description

The CKP reference signal is produced by the crankshaft

position (CKP) sensor . During one crankshaft revolution,

CKP crankshaft reference pulses will be produced. The

Engine Control Module ECM uses the CKP reference

signal to calculate engine RPM and crankshaft position.

The ECM constantly monitors the number of pulses on

the CKP reference circuit and compares them to the

number of camshaft position (CMP) signal pulses being

received. If the ECM does not receive pulses on the CKP

reference circuit, DTC P0337 will set.

Conditions for Setting the DTC

DIgnition SW is ON.

DThe battery voltage is more than 11 volts.

DEngine running speed is below 2000 r.p.m.

DThe CKP pulse reading is 10 for 10th.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) after the second consecutive trip in which the

fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0337 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0337 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

An intermittent may be caused by a poor connection,

rubbed-through wire insulation or a wire broken inside the

insulation. Check for:

DPoor connection – Inspect the ECM harness and

connectors for improper mating, broken locks,

improperly formed or damaged terminals, and poor

terminal-to-wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, disconnect

the ECM, turn the ignition on and observe a voltmeter

connected to the CKP reference circuit at the ECM

harness connector while moving connectors and

wiring harnesses related to the ICM. A change in

voltage will indicate the location of the fault.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P0337 – CKP Sensor Circuit Low Frequency

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Attempt to start the engine.

Does the engine start? —Go to

Step 3

Go to

Chart 3

31. Review and record Failure Records information.

2. Clear DTC P0337.

3. Start the engine and idle for 1 minute.

4. Observe DTCs.

Is DTC P0337 set? —Go to

Step 4

Refer to

Diagnostic

Aid

41. Disconnect the CKP sensor.

2. Ignition “ON.”

3. Using a DVM, verify that 5 V reference and ground

are being supplied at the sensor connector (ECM

side).

Are 4-6 volts and ground available at the sensor? —Go to

Step 7

Go to

Step 5

51. Ignition “ON.”

2. With a DVM, backprobe the ECM connector 5 V

reference and ground connections.

Are 5 V reference and ground available at the ECM? —Go to

Step 6

Go to

Step 11

6Check 5 V reference or ground between the CKP

sensor and ECM and repair the open circuit, short to

ground or short to voltage.

Is the action complete? — Verify repair —

71. Ignition “OFF.”

2. Disconnect the ECM and CKP sensor.

3. Check for an open or a short to ground in the CKP

reference circuit between the CKP sensor

connector and the ECM harness connector.

4. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 8

81. Reconnect the ECM and CKP sensor.

2. Connect a DVM to measure voltage on the CKP

reference circuit at the ECM connector.

3. Observe the voltage while cranking the engine.

Is the voltage near the specified value? 2.5 V Go to

Step 11

Go to

Step 9

9Check the connections at the CKP sensor and replace

the terminals if necessary.

Did any terminals require replacement? — Verify repair Go to

Step 10

10 Replace the CKP sensor. Use caution and avoid hot oil

that may drip out.

Is the action complete? — Verify repair —

Step Action Value(s) Yes No

11 Check the connections at the ECM and replace the

terminals as necessary.

Did any terminals require replaceme nt? – Verify repair Go to Step 12

12 Replace the ECM.

Is the action complete? – Verify repair –

P0341 CMP Sensor Circuit Performance

060RM077

Circuit Description

The CMP signal is produced by the camshaft position

(CMP) sensor pulses when the engine is running and

crankshaft position (CKP) sync pulses are also being

received.

The Engine Control Module ECM uses the CMP signal

pulses to initiate sequential fuel injection. The ECM

constantly monitors the number of pulses on the CMP

signal circuit and compares the number of CMP pulses

to the number of reference pulses receiv ed.

If the ECM receives an incorrect number of pulses on

the CMP reference circuit, DTC P0341 will set and the

ECM will initiate injector sequence without the CMP

signal, with a one in six chance that injector sequence

is correct.

The engine will continue to start and run normally,

although the misfire diagnostic will be affected if a

misfiring condition occurs.

Conditions for Setting the DTC

• The engine is running.

• The battery voltage is more than 11 volts.

• No related CKP DTCs.

• CMP pulse is not synchronized with CKP pulse for

20th.

Action Taken When the DTC Sets

• The ECM will illuminate the malfunction indicator

lamp (MIL) after the second consecutive trip in

which the fault is detected.

• The ECM will initia te th e injector seque nce witho u t the

CMP signal with a one in six chance that the injector

sequence is correct.

• The ECM will store con ditions w hich were presen t when

the DTC was set, as Freeze Frame and in the Failure

Records data.

Conditions for Clearing the MIL/DTC

• The ECM will turn the MIL "OFF" on the third

consecutive trip cycle during which the diagnostic has

been run and the fault con dition is no longer present.

• A history DTC P0341 will clear after 40 consecutive

warm-up cy cle s have occurred w ithout a fau lt.

• D TC P0341 can be cleared by using the Tech 2 "Clear

Info" fun cti on or by discon ne cting the EC M battery feed .

Diagnostic Aids

An intermittent may be caused by a poo r connection,

rubbed-through wire insulation or a wire broken inside the

insulation. Check for:

• Poor connection - Inspe ct th e ECM harne ss and

connectors for imprope r mating, broken locks,

improperly formed or damage d termin al s, and poor

terminal-to-wire conn ection.

• Damaged harness - Inspect the wiring harness for

damage. If the harn ess appears to be OK, disconnect

the ECM, turn the ignition on and observe a voltmeter

connected to the CMP sign al circui t at the ECM

harness connector while moving co nnecto rs and wiring

harnesses related to the ECM and the CMP sensor. A

change in voltage will indica te the location o f the fault.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often the

condition that caused the DTC to be set occurs. This may

assist in diagnosin g the cond i tion.

NOTE: On early-built TFR/S, the Tech 2 indication for "CMP

ACT. COUNTER" (Ca m Position Sensor activity) will

continue to count up, even if no cam position signal i s being

received by the ECM.

Test Description

Number(s) below refer to the step nu mber (s) on the

Diagnostic Chart.

2. Ensures that the fault is present.

12. Determines whether the fault is being caused by a

faulty sensor. The Te ch 2 read ing shoul d toggle

between 4 volts, to near 0 volts, as the screwdriver

blade is wiped across the sensor end .

P0341 CMP Sensor Circuit Performance

Step Action Value(s) Yes No

1 Was the “On-Board Diagnostic (OBD) System

Check” performed? – Go to Step 2 Go to OBD

System Check

2 1. Ignition "ON."

2. Review and record Tech 2 Failure Records

data.

3. Operate the vehicle within Failure Records

conditions as noted.

4. Using Tech 2, monitor "DTC" info for DTC

P0341 until the DTC P0341 test runs.

5. Note the test result.

Does Tech 2 indicate DTC P0341 failed this

ignition? – Go to Step 3 Refer to

Diagnostic Aids

3 1. Disconnect the CMP sensor.

2. Measure the voltage between the sensor

feed circuit and the sensor ground circuit at

the CMP sensor harness connector.

Does the voltage measure near the specified

value? 4 – 6 V Go to Step 4 Go to Step 5

4 Measure the voltage between the CMP sensor

signal circuit and the sensor ground circuit at the

CMP sensor harness connector.

Does the voltage measure near the specified

value? 4 – 6 V Go to Step 11 Go to Step

5 If the voltage measured in step 3 was less than 4

– 6 volts, proceed directly to step 6 without

completing this step.

If the voltage in step 3 was greater than 4 – 6 V,

repair the short to voltage in the CMP feed circuit.

Is the action complete? – Verify repair –

6 1. Check for poor connections at the camshaft

position sensor.

2. If a problem is found, repair as necessary.

Was a problem found? – Verify repair Go to Step 7

Step Action Value(s) Yes No

7 1. Ignition ‘OFF’ disconnect the ECM and the

CMP sensor.

2. Check the following circuits for an open

between the ignition control module and the

CMP sensor:

• The sensor feed circuit.

3. If a problem is found, repair as necessary.

Was a problem found? – Verify repair Go to Step 9

8 1. Ignition ‘OFF’, disconnect the ECM (leave the

CMP sensor disconnected).

2. Ignition ‘ON’, check the following circuits:

• The CMP sensor signal circuit for an open

or a short to voltage.

• The CMP sensor input signal circuit for a

short to ground.

3. If a problem is found, repair it as necessary.

Was a problem found? – Verify repair Go to Step 9

9 Check for a short or open in the sensor ground

circuit.

Was a problem found and corrected? – Verify repair Go to Step 10

10 1. Check for poor connections at the PCM.

2. If a problem is found, repair as necessary.

Was a problem found? – Verify repair Go to Step 11

11 Backprobe the ECM connector with a DMM to

monitor voltage on the camshaft position input

signal circuit while cranking the engine with the

sensor connected.

(Use a rubber band, tape, or an assistant to keep

the DMM lead in contact with the sensor terminal

during this test.)

Does the voltage toggle between the specified

values? 4 – 0 V Go to Step 14 Go to Step 12

12 1 Disconnect the CMP wiring harness

connector.

2. Remove the CMP sensor, then reconnect the

wiring harness connector.

3. Turn ignition ‘ON’.

4. Move the shank of a large screwdriver back

and forth across the face of the sensor, (close

but not touching).

5. Monitor the CMP signal on the Tech 2 Data

Display.

Does the voltage signal vary as specified?

Fluctuates

between

0 and 4

volts Go to Step 14 Go to Step 13

13 Replace the camshaft position sensor.

Is the action complete? – Verify repair –

14 Replace the ECM.

Is the action complete? – Verify repair –

P0342 CMP Sensor Circuit Low

060RW077

Circuit Description

The CMP signal produced by the camshaft position

(CMP) sensor pulses when the engine is running and

crankshaft position (CKP) sync pulses are also being

received. The hall type CMP sensor and the CKP sensor

share 5 V and ground connections at the Engine Control

Module ECM. The third wire at the sensor is a signal

circuit to the ECM. The ECM uses the CMP signal pulses

to initiate sequential fuel injection. The ECM constantly

monitors the number of pulses on the CMP signal circuit

and compares the number of CMP pulses to the number

of 58X reference pulses received. If the ECM does not

receive pulses on the CMP reference circuit, DTC P0342

will set and the ECM will initiate injector sequence without

the CMP signal with a one in six chance that injector

sequence is correct. The engine will continue to start and

run normally, although the misfire diagnostic will be

affected if a misfiring condition occurs.

Conditions for Setting the DTC

DThe engine is running.

DThe battery is more than 11 volts.

DNo related CKP DTCs.

DCMP pulse reverse one’s couse for 20th.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) after the second consecutive trip in which the

fault is detected.

DThe ECM will initiate injector sequence without the

CMP signal with a one in six chance that the injector

sequence is correct.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0342 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0342 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

An intermittent may be caused by a poor connection,

rubbed-through wire insulation or a wire broken inside the

insulation. Check for:

DPoor connection – Inspect the ECM harness and

connectors for improper mating, broken locks,

improperly formed or damaged terminals, and poor

terminal to wire connection.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, disconnect

the ECM, turn the ignition on and observe a voltmeter

connected to the CMP signal circuit at the ECM

harness connector while moving connectors and

wiring harnesses related to the ICM and the CMP

sensor. A change in voltage will indicate the location

of the fault.

NOTE: On early-built TFR/S, the Tech 2 indication for

“CMP ACT. COUNTER” (Cam Position Sensor activity)

will continue to count up, even if no cam position signal is

being received by the ECM.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

2. Ensures that the fault is present.

14.Determines whether the fault is being caused by a

missing camshaft magnet or a faulty ECM. The

voltage measured in this step should read around 4

volts, toggling to near 0 volts when the CMP sensor

interfaces with the camshaft magnet.

DTC P0342 —CMP Sensor Circuit Low

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor “DTC” information for DTC

P0342 until the DTC P0342 test runs.

5. Note test result.

Does the Tech 2 indicate DTC P0342 failed this

ignition? — Go to

Step 3

Refer to

Diagnostic

Aids

31. Ignition “ON.”

2. Disconnect the CMP sensor.

3. Measure the voltage between the sensor feed

circuit and the sensor ground circuit at the CMP

sensor harness connector.

Does the voltage measure near the specified value? 4-6 V Go to

Step 7

Go to

Step 4

41. Ignition “OFF,” disconnect the ECM and the CMP

sensor.

2. Check for poor connections at the camshaft

position sensor.

3. If a problem is found, repair it as necessary.

Was a problem found? — Verify repair Go to

Step 5

51. Check for poor connections at the ECM.

2. If a problem is found, repair it as necessary.

Was a problem found? — Verify repair Go to

Step 6

61. Check the following circuits between the ECM and

the CMP sensor:

DThe sensor feed circuit. Open or short to

ground?

DThe sensor ground circuit. Open or short to

voltage?

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair —

71. Ignition “ON,” engine “OFF.”

2. Measure the voltage between the CMP sensor

signal circuit and the sensor ground circuit at the

CMP sensor harness connector.

Does the voltage measure near the specified value? 4-6 V Go to

Step 8

Go to

Step 9

Step NoYesValue(s)Action

81. Turn the ignition “OFF.”

2. Disconnect the ECM and connect a DVM to monitor

voltage on the camshaft position signal circuit at the

ECM connector.

3. Ignition “ON.”

4. Monitor the voltage display on the DVM while

repeatedly touching the CMP sensor signal circuit

at the CMP sensor connector with a test light to

ground.

Does the DVM voltage display switch between 0 and

approximately 5 volts when the test light is touched to

the CMP sensor signal circuit? —Go to

Step 12

Go to

Step 9

91. Ignition “OFF.”

2. Leave the ECM disconnected.

3. Ignition “ON.”

4. Probe the camshaft position signal circuit at the

ECM connector with a test light to B+.

5. If the test light is “ON,” locate and repair the short to

ground in the camshaft position input signal circuit.

Was either circuit shorted to ground? — Verify repair Go to

Step 10

10 1. Ignition “OFF.”

2. Leave the ECM disconnected.

3. Ignition “ON.”

4. Probe the camshaft position signal circuit with a test

light to ground.

5. If the test light is “ON,” locate and repair the short to

voltage in the camshaft position input signal circuit.

Was the test light “ON”? — Verify repair Go to

Step 11

11 1. Ignition “OFF,” disconnect the ECM (leave the CMP

sensor disconnected).

2. Ignition “ON,” check the following circuit:

DThe CMP sensor signal circuit for an open.

3. If a problem is found, repair it as necessary.

Was a problem found? — Verify repair —

12 1. Ignition “ON.”

2. Remove the CMP sensor from the engine front

cover (leave the sensor wiring connected).

3. Place a magnet on the CMP sensor. If you use a

magnet that is too small to cover the face of the

sensor, test on every part of the sensor face

because only a small area will respond to this test.

Does the DVM display a voltage near the specified

value? 0 V Go to

Step 14

Go to

Step 13

13 Replace the camshaft position sensor.

Is the action complete? — Verify repair —

14 1. Reinstall the CMP sensor to the engine front cover .

2. Observe the DVM connected to monitor voltage on

the camshaft position signal circuit while cranking

the engine.

Does the voltage toggle between the specified values? 4-0 V Go to

Step 15

Go to

Step 16

Step NoYesValue(s)Action

15 Replace the ECM.

Is the action complete? — Verify repair —

16 Replace faulty or missing camshaft magnet.

Is the action complete? — Verify repair —

P0351 Ignition 1 Control Circuit

060RW075

Circuit Description

The Engine Control Module’s ECM control circuit 1

provides a zero-volt or a 5-volt output signal to the ignition

coil. The normal voltage on the circuit is zero volts. When

the ignition coil receives the 5-volt signal from the ECM, it

provides a ground path for the B+ supply to the primary

side of the number 1 ignition coil. When the ECM shuts off

the 5 volts to the ignition coil, the ignition coil turns “OFF.”

This causes the ignition coil primary magnetic field to

collapse, producing a voltage in the secondary coil which

fires the spark plug.

The circuit between the ECM and ignition coil is monitored

for an open circuit, short to voltage, and short to ground.

When the ECM detects a problem on ignition control

circuit 1, it will set a DTC P0351.

Conditions for Setting the DTC

DThe ignition is “ON.”

DThe engine is turning, determined by the crankshaft

position input signal.

DEngine running speed is between 200 r.p.m and 850

r.p.m.

DSpark signal don’t present 6 samples of continuous.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle in which the diagnostic has been

run and the fault condition is no longer present.

DA history DTC P0351 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0351 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect the harness

connectors for backed-out terminals, improper mating,

broken locks, improperly formed or damaged

terminals, and poor terminal-to-wire connections.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

Tech 2 display related to DTC P0351 while moving the

connector and wiring related to the ignition system. A

change in the display will indicate the location of the

fault.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P0351 – Ignition 1 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Record

conditions as noted.

4. Use a Tech 2 to monitor the “DTC” information for

DTC P0351 until the DTC P0351 test runs.

5. Note the test result.

Does the T ech 2 indicate DTC P0351 failed this ignition

cycle? — Go to

Step 3

Go to

Diagnostic

Aids

3Check for faulty connection at ignition coil.

Was a problem found? — Verify repair Go to

Step 4

4Check for faulty connection at ECM connector.

Was a problem found? — Verify repair Go to

Step 5

51. Ignition “ON,” engine “OFF.”

2. Back probe the ignition control circuit 1 at the ECM

with a DVM.

Is the voltage near the specified value? 25-55 mV Go to

Step 6

Go to

Step 9

61. Ignition “ON,” engine running.

2. Back probe the ignition control circuit at the ECM for

the cylinder being tested.

Is the voltage in the specified range, rapidly toggling

back and forth to a reading 20-50 mV higher? 100-180 mV Go to

Step 7

Go to

Step 13

71. Ignition “OFF.”

2. Disconnect the 3-pin and 5-pin connectors at the

ignition coil.

3. Check ignition control circuit 1 voltage at the ignition

coil connector while cranking the engine.

Does the voltage measure between the specified

values? 200-1200 mV Go to

Step 8

Go to

Step 11

8Replace the ignition coil.

Is the action complete? — Verify repair —

91. Ignition “OFF.”

2. Disconnect the ECM and the ignition coil.

3. Check ignition control circuit 1 for short to ground.

Was a problem found? — Verify repair Go to

Step 10

10 Check ignition control circuit 1 for short to voltage.

Was a problem found? — Verify repair Go to

Step 13

Step NoYesValue(s)Action

11 Check for an open ignition control circuit 1.

Was the ignition control circuit open? —Go to

Step 12

Go to

Step 13

12 Repair the open ignition control circuit.

Is the action complete? — Verify repair —

13 Replace the ECM.

Is the action complete? — Verify repair —

P0352 Ignition 2 Control Circuit

060RW075

Circuit Description

The engine control module’s (ECM) control circuit 2

provides a zero-volt or a 5-volt output signal to the ignition

coil. The normal voltage on the circuit is zero volts. When

the ignition coil receives the 5-volt signal from the ECM, it

provides a ground path for the B+ supply to the primary

side of the number 2 ignition coil. When the ECM shuts off

the 5 volts to the ignition coil, the ignition coil turns “OFF.”

This causes the ignition coil primary magnetic field to

collapse, producing a voltage in the secondary coil which

fires the spark plug.

The circuit between the ECM and ignition coil is monitored

for an open circuit, short to voltage, and short to ground.

When the ECM detects a problem on ignition control

circuit 2, it will set a DTC P0352.

Conditions for Setting the DTC

DThe ignition is “ON.”

DThe engine is turning, determined by the crankshaft

position input signal.

DEngine running speed is between 200 r.p.m and 850

r.p.m.

DSpark signal don’t present 6 samples of continuous.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle in which the diagnostic has been

run and the fault condition is no longer present.

DA history DTC P0352 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0352 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect the harness

connectors for backed-out terminals, improper mating,

broken locks, improperly formed or damaged

terminals, and poor terminal-to-wire connections.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

Tech 2 display related to DTC P0352 while moving the

connector and wiring related to the ignition system. A

change in the display will indicate the location of the

fault.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P0352 – Ignition 2 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Record

conditions as noted.

4. Use a Tech 2 to monitor the “DTC” information for

DTC P0352 until the DTC P0352 test runs.

5. Note the test result.

Does the T ech 2 indicate DTC P0352 failed this ignition

cycle? — Go to

Step 3

Go to

Diagnostic

Aids

3Check for faulty connection at ignition coil.

Was a problem found? — Verify repair Go to

Step 4

4Check for faulty connection at ECM connector.

Was a problem found? — Verify repair Go to

Step 5

51. Ignition “ON,” engine “OFF.”

2. Back probe the ignition control circuit 2 at the ECM

with a DVM .

Is the voltage near the specified value? 25-55 mV Go to

Step 6

Go to

Step 9

61. Ignition “ON,” engine running.

2. Back probe the ignition control circuit at the ECM for

the cylinder being tested.

Is the voltage in the specified range, rapidly toggling

back and forth to a reading 20-50 mV higher? 100-180 mV Go to

Step 7

Go to

Step 13

71. Ignition “OFF.”

2. Disconnect the 3-pin and 5-pin connectors at the

ignition coil.

3. Check ignition control circuit 2 voltage at the ignition

coil connector while cranking the engine connector .

Does the voltage measure between the specified

values? 200-1200 mV Go to

Step 8

Go to

Step 11

8Replace the ignition coil.

Is the action complete? — Verify repair —

91. Ignition “OFF.”

2. Disconnect the ECM and the ignition coil.

3. Check ignition control circuit 2 for short to ground.

Was a problem found? — Verify repair Go to

Step 10

Step NoYesValue(s)Action

10 Check ignition control circuit 2 for short to voltage.

Was a problem found? — Verify repair Go to

Step 13

11 Check for an open ignition control circuit 2.

Was the ignition control circuit open? —Go to

Step 12

Go to

Step 13

12 Repair the open ignition control circuit.

Is the action complete? — Verify repair —

13 Replace the ECM.

Is the action complete? — Verify repair —

P0353 Ignition 3 Control Circuit

060RW075

Circuit Description

The engine control module’s (ECM) control circuit 3

provides a zero-volt or a 5-volt output signal to the ignition

coil. The normal voltage on the circuit is zero volts. When

the ignition coil receives the 5-volt signal from the ECM, it

provides a ground path for the B+ supply to the primary

side of the number 3 ignition coil. When the ECM shuts off

the 5 volts to the ignition coil, the ignition coil turns “OFF.”

This causes the ignition coil primary magnetic field to

collapse, producing a voltage in the secondary coil which

fires the spark plug.

The circuit between the ECM and ignition coil is monitored

for an open circuit, short to voltage, and short to ground.

When the ECM detects a problem on ignition control

circuit 3, it will set a DTC P0353.

Conditions for Setting the DTC

DThe ignition is “ON.”

DThe engine is turning, determined by the crankshaft

position input signal.

DEngine running speed is between 200 r.p.m and 850

r.p.m.

DSpark signal don’t present 6 samples of continuous.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle in which the diagnostic has been

run and the fault condition is no longer present.

DA history DTC P0353 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0353 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect the harness

connectors for backed-out terminals, improper mating,

broken locks, improperly formed or damaged

terminals, and poor terminal-to-wire connections.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

Tech 2 display related to DTC P0353 while moving the

connector and wiring related to the ignition system. A

change in the display will indicate the location of the

fault.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P0353 – Ignition 3 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Record

conditions as noted.

4. Use a Tech 2 to monitor the “DTC” information for

DTC P0353 until the DTC P0353 test runs.

5. Note the test result.

Does the T ech 2 indicate DTC P0353 failed this ignition

cycle? — Go to

Step 3

Go to

Diagnostic

Aids

3Check for faulty connection at ignition coil.

Was a problem found? — Verify repair Go to

Step 4

4Check for faulty connection at ECM connector.

Was a problem found? — Verify repair Go to

Step 5

51. Ignition “ON,” engine “OFF.”

2. Back probe the ignition control circuit 3 at the ECM

with a DVM.

Is the voltage near the specified value? 25-55 mV Go to

Step 6

Go to

Step 9

61. Ignition “ON,” engine running.

2. Back probe the ignition control circuit at the ECM for

the cylinder being tested.

Is the voltage in the specified range, rapidly toggling

back and forth to a reading 20-50 mV higher? 100-180 mV Go to

Step 7

Go to

Step 13

71. Ignition “OFF.”

2. Disconnect the 3-pin and 5-pin connectors at the

ignition coil.

3. Check ignition control circuit 3 voltage at the ignition

coil connector while cranking the engine.

Does the voltage measure between the specified

values? 200-1200 mV Go to

Step 8

Go to

Step 11

8Replace the ignition coil.

Is the action complete? — Verify repair —

91. Ignition “OFF.”

2. Disconnect the ECM and the ignition coil.

3. Check ignition control circuit 3 for short to ground.

Was a problem found? — Verify repair Go to

Step 10

Step NoYesValue(s)Action

10 Check ignition control circuit 3 for short to voltage.

Was a problem found? — Verify repair Go to

Step 13

11 Check for an open ignition control circuit 3.

Was the ignition control circuit open? —Go to

Step 12

Go to

Step 13

12 Repair the open ignition control circuit.

Is the action complete? — Verify repair —

13 Replace the ECM.

Is the action complete? — Verify repair —

P0354 Ignition 4 Control Circuit

060RW075

Circuit Description

The engine control module’s (ECM) control circuit 4

provides a zero-volt or a 5-volt output signal to the ignition

coil. The normal voltage on the circuit is zero volts. When

the ignition coil receives the 5-volt signal from the ECM, it

provides a ground path for the B+ supply to the primary

side of the number 4 ignition coil. When the ECM shuts off

the 5 volts to the ignition coil, the ignition coil turns “OFF.”

This causes the ignition coil primary magnetic field to

collapse, producing a voltage in the secondary coil which

fires the spark plug.

The circuit between the ECM and ignition coil is monitored

for an open circuit, short to voltage, and short to ground.

When the ECM detects a problem on ignition control

circuit 4, it will set a DTC P0354.

Conditions for Setting the DTC

DThe ignition is “ON.”

DThe engine is turning, determined by the crankshaft

position input signal.

DEngine running speed is between 200 r.p.m and 850

r.p.m.

DSpark signal don’t present 6 samples of continuous.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle in which the diagnostic has been

run and the fault condition is no longer present.

DA history DTC P0354 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0354 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect the harness

connectors for backed-out terminals, improper mating,

broken locks, improperly formed or damaged

terminals, and poor terminal-to-wire connections.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

Tech 2 display related to DTC P0354 while moving the

connector and wiring related to the ignition system. A

change in the display will indicate the location of the

fault.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P0354 – Ignition 4 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Record

conditions as noted.

4. Use a Tech 2 to monitor the “DTC” information for

DTC P0354 until the DTC P0354 test runs.

5. Note the test result.

Does the T ech 2 indicate DTC P0354 failed this ignition

cycle? — Go to

Step 3

Go to

Diagnostic

Aids

3Check for faulty connection at ignition coil.

Was a problem found? — Verify repair Go to

Step 4

4Check for faulty connection at ECM connector.

Was a problem found? — Verify repair Go to

Step 5

51. Ignition “ON,” engine “OFF.”

2. Back probe the ignition control circuit 4 at the ECM

with a DVM.

Is the voltage near the specified value? 25-55 mV Go to

Step 6

Go to

Step 9

61. Ignition “ON,” engine running.

2. Back probe the ignition control circuit at the ECM for

the cylinder being tested.

Is the voltage in the specified range, rapidly toggling

back and forth to a reading 20-50 mV higher? 100-180 mV Go to

Step 7

Go to

Step 13

71. Ignition “OFF.”

2. Disconnect the 3-pin and 5-pin connectors at the

ignition coil.

3. Check ignition control circuit 4 voltage at the ignition

coil connector while cranking the engine.

Does the voltage measure between the specified

values? 200-1200 mV Go to

Step 8

Go to

Step 11

8Replace the ignition coil.

Is the action complete? — Verify repair —

91. Ignition “OFF.”

2. Disconnect the ECM and the ignition coil.

3. Check ignition control circuit 4 for short to ground.

Was a problem found? — Verify repair Go to

Step 10

Step NoYesValue(s)Action

10 Check ignition control circuit 4 for short to voltage.

Was a problem found? — Verify repair Go to

Step 13

11 Check for an open ignition control circuit 4.

Was the ignition control circuit open? —Go to

Step 12

Go to

Step 13

12 Repair the open in ignition control circuit.

Is the action complete? — Verify repair —

13 Replace the ECM.

Is the action complete? — Verify repair —

P0355 Ignition 5 Control Circuit

060RW075

Circuit Description

The engine control module’s (ECM) control circuit 5

provides a zero-volt or a 5-volt output signal to the ignition

coil. The normal voltage on the circuit is zero volts. When

the ignition coil receives the 5-volt signal from the ECM, it

provides a ground path for the B+ supply to the primary

side of the number 5 ignition coil. When the ECM shuts off

the 5 volts to the ignition coil, the ignition coil turns “OFF.”

This causes the ignition coil primary magnetic field to

collapse, producing a voltage in the secondary coil which

fires the spark plug.

The circuit between the ECM and ignition coil is monitored

for an open circuit, short to voltage, and short to ground.

When the ECM detects a problem on ignition control

circuit 5, it will set a DTC P0355.

Conditions for Setting the DTC

DThe ignition is “ON.”

DThe engine is turning, determined by the crankshaft

position input signal.

DEngine running speed is between 200 r.p.m and 850

r.p.m.

DSpark signal don’t present 6 samples of continuous.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle in which the diagnostic has been

run and the fault condition is no longer present.

DA history DTC P0355 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0355 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect the harness

connectors for backed-out terminals, improper mating,

broken locks, improperly formed or damaged

terminals, and poor terminal-to-wire connections.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

Tech 2 display related to DTC P0355 while moving the

connector and wiring related to the ignition system. A

change in the display will indicate the location of the

fault.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P0355 – Ignition 5 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Record

conditions as noted.

4. Use a Tech 2 to monitor the “DTC” information for

DTC P0355 until the DTC P0355 test runs.

5. Note the test result.

Does the T ech 2 indicate DTC P0355 failed this ignition

cycle? — Go to

Step 3

Go to

Diagnostic

Aids

3Check for faulty connection at ignition coil.

Was a problem found? — Verify repair Go to

Step 4

4Check for faulty connection at ECM connector.

Was a problem found? — Verify repair Go to

Step 5

51. Ignition “ON,” engine “OFF.”

2. Back probe the ignition control circuit 5 at the ECM

with a DVM.

Is the voltage near the specified value? 25-55 mV Go to

Step 6

Go to

Step 9

61. Ignition “ON,” engine running.

2. Back probe the ignition control circuit at the ECM for

the cylinder being tested.

Is the voltage in the specified range, rapidly toggling

back and forth to a reading 20-50 mV higher? 100-180 mV Go to

Step 7

Go to

Step 13

71. Ignition “OFF.”

2. Disconnect the 3-pin and 5-pin connectors at the

ignition coil.

3. Check ignition control circuit 5 voltage at the ignition

coil connector while cranking the engine.

Does the voltage measure between the specified

values? 200-1200 mV Go to

Step 8

Go to

Step 11

8Replace the ignition coil.

Is the action complete? — Verify repair —

91. Ignition “OFF.”

2. Disconnect the ECM and the ignition coil.

3. Check ignition control circuit 5 for short to ground.

Was a problem found? — Verify repair Go to

Step 10

Step NoYesValue(s)Action

10 Check ignition control circuit 5 for short to voltage.

Was a problem found? — Verify repair Go to

Step 13

11 Check for an open ignition control circuit 5.

Was the ignition control circuit open? —Go to

Step 12

Go to

Step 13

12 Repair the open ignition control circuit.

Is the action complete? — Verify repair —

13 Replace the ECM.

Is the action complete? — Verify repair —

P0356 Ignition 6 Control Circuit

060RW075

Circuit Description

The engine control module’s (ECM) control circuit 6

provides a zero-volt or a 5-volt output signal to the ignition

coil. The normal voltage on the circuit is zero volts. When

the ignition coil receives the 5-volt signal from the ECM, it

provides a ground path for the B+ supply to the primary

side of the number 6 ignition coil. When the ECM shuts off

the 5 volts to the ignition coil, the ignition coil turns “OFF.”

This causes the ignition coil primary magnetic field to

collapse, producing a voltage in the secondary coil which

fires the spark plug.

The circuit between the ECM and ignition coil is monitored

for an open circuit, short to voltage, and short to ground.

When the ECM detects a problem on ignition control

circuit 6, it will set a DTC P0356.

Conditions for Setting the DTC

DThe ignition is “ON.”

DThe engine is turning, determined by the crankshaft

position input signal.

DEngine running speed is between 200 r.p.m and 850

r.p.m.

DSpark signal don’t present 6 samples of continuous.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle in which the diagnostic has been

run and the fault condition is no longer present.

DA history DTC P0356 will clear after 40 consecutive

warm-up cycles occur without a fault.

DDTC P0356 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM – Inspect the harness

connectors for backed-out terminals, improper mating,

broken locks, improperly formed or damaged

terminals, and poor terminal-to-wire connections.

DDamaged harness – Inspect the wiring harness for

damage. If the harness appears to be OK, observe the

Tech 2 display related to DTC P0356 while moving the

connector and wiring related to the ignition system. A

change in the display will indicate the location of the

fault.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P0356 – Ignition 6 Control Circuit

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Ignition “ON,” engine “OFF.”

2. Review and record Tech 2 Failure Records data.

3. Operate the vehicle within Failure Record

conditions as noted.

4. Use a Tech 2 to monitor the “DTC” information for

DTC P0356 until the DTC P0356 test runs.

5. Note the test result.

Does the T ech 2 indicate DTC P0356 failed this ignition

cycle? — Go to

Step 3

Go to

Diagnostic

Aids

3Check for faulty connection at ignition coil.

Was a problem found? — Verify repair Go to

Step 4

4Check for faulty connection at ECM connector.

Was a problem found? — Verify repair Go to

Step 5

51. Ignition “ON,” engine “OFF.”

2. Back probe the ignition control circuit 6 at the ECM

with a DVM.

Is the voltage near the specified value? 25-55 mV Go to

Step 6

Go to

Step 9

61. Ignition “ON,” engine running.

2. Back probe the ignition control circuit at the ECM for

the cylinder being tested.

Is the voltage in the specified range, rapidly toggling

back and forth to a reading 20-50 mV higher? 100-180 mV Go to

Step 7

Go to

Step 13

71. Ignition “OFF.”

2. Disconnect the 3-pin and 5-pin connectors at the

ignition coil.

3. Check ignition control circuit 6 voltage at the ignition

coil connector while cranking the engine.

Does the voltage measure between the specified

values? 200-1200 mV Go to

Step 8

Go to

Step 11

8Replace the ignition coil.

Is the action complete? — Verify repair —

91. Ignition “OFF.”

2. Disconnect the ECM and the ignition coil.

3. Check ignition control circuit 6 for short to ground.

Was a problem found? — Verify repair Go to

Step 10

Step NoYesValue(s)Action

10 Check ignition control circuit 6 for short to voltage.

Was a problem found? — Verify repair Go to

Step 13

11 Check for an open ignition control circuit 6.

Was the ignition control circuit open? —Go to

Step 12

Go to

Step 13

12 Repair the open ignition control circuit.

Is the action complete? — Verify repair —

13 Replace the ECM.

Is the action complete? — Verify repair —

P0502 VSS No Signal

060RW052

Circuit Description

The vehicle speed sensor has a magnet rotated by the

transmission output shaft. Attached to the sensor is a hall

effect circuit the interacts with the magnetic field treated

by the rotating magnet. A 12-volt operating supply for the

speed sensor hall circuit is supplied from the meter fuse.

The VSS pulses to ground the 9-volt signal sent from the

engine control module (ECM) on the reference circuit.

The ECM interprets vehicle speed by the number of

pulses to ground per second on the reference circuit.

Conditions for Setting the DTC

DEngine is running.

DEngine speed is below 5000 RPM.

DFuel is cutting.

DV ehicle speed is below 1Km/H for more than 4 second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first time the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0502 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0502 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

9. To avoid backprobing the VSS and possibly

damaging a seal or terminal, the VSS output can be

tested at the point where the transmission harness

connected to the engine harness. The green 16-way

connector is adjacent to a blue 16-way connector,

and it can be easily accessed by removing the air

cleaner assembly. The green 16-way connector is

separated, and battery voltage is applied to the VSS

through the yellow wire at one corner of the

connector. The VSS output can be monitored with a

DVM connected to the blue wire with a black tracer.

The two wires are next to each other in the 16-way

connector . The test connections are made on the

transmission side of the connector, the side that is

not clipped to the body sheetmetal.

14. The speedometer-to-ECM VSS signal wire is

spliced to a wire leading to the cruise control

module. If a short to ground or voltage is found

between the ECM and speedometer, it could be

located between the splice and the cruise control

module.

DTC P0502 –VSS Circuit Low Input

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Does the speedometer work? —Go to

Step 10

Go to

Step 3

31. Disconnect the VSS connector.

2. Ignition “ON.”

3. Using a test light to battery +, probe the connector

ground wire.

Did the light illuminate? —Go to

Step 5

Go to

Step 4

4Repair the sensor ground.

Is the action complete? — Verify repair —

51. Ignition “ON,” sensor disconnected.

2. Using a DVM, measure at the VSS connector

between ground and voltage supply.

Was the measurement near the specified value? Battery

voltage Go to

Step 7

Go to

Step 6

6Repair the open or short to ground which may have

blown the meter fuse.

Is the action complete? — Verify repair —

71. Ignition “ON,” VSS disconnected.

2. Using a DVM, measure at the VSS connector

between ground and the blue/black wire from the

speedometer.

Was the measurement near the specified value? 7.5-8 V Go to

Step 9

Go to

Step 8

8Check for an open or short circuit between the

speedometer and the VSS.

Was an open or short circuit located? — Verify repair Go to

Step 9

9Replace the speedometer.

Is the action complete? — Verify repair —

Step NoYesValue(s)Action

10 1. Ignition “OFF.”

2. Disconnect the MAF sensor and remove the air

cleaner assembly and filter element to gain access

to the 16-way green connector located immediately

to the rear of the left front headlamp. The connector

attaches the VSS wires from the transmission

harness to the left-side engine harness.

3. Disconnect the green 16-way connector.

4. Select a terminal adapter from kit 5-8840-0385-0

that can be used with a jumper to supply B+ to the

yellow (transmission side of the connector). There

are 2 yellow wires at that connector , but the correct

one is in the corner position.

5. Use another terminal adapter to attach a voltmeter

to the blue wire with a black tracer (next to the wire in

the previous step.)

6. At the transmission side of the green 16-way

connector, locate the black wire next to the VSS

yellow ign+ wire. The black wire is the VSS ground

wire. Use a terminal adapter to attach a jumper to

ground to the black VSS ground wire at the

transmission side of the connector.

7. Raise the rear wheels off the ground with

transmission in neutral.

Does the DVM toggle back and forth between 0.6 V and

10 V as the wheels (and driveshaft) are rotated? —Go to

Step 12

Go to

Step 11

11 Replace the VSS.

Is the action complete? — Verify repair —

12 Check for an open or short between the ECM and the

speedometer.

Was a problem found? — Verify repair Go to

Step 13

13 Replace the ECM.

Is the action complete? — Verify repair —

P0562 System Voltage Low

Circuit Description

The engine control module (ECM) monitors the system

voltage on the ignition feed terminals to the ECM. A

system voltage DTC will set whenever the voltage is

above a calibrated value.

Conditions for Setting the DTC

DEngine is running.

DSystem voltage is below 6 volts for more than 20

second.

Action Taken When the DTC Sets

DThe ECM will not illuminate the malfunction indicator

lamp (MIL).

DThe ECM will store as Failure Records only conditions

which were present when the DTC was set. This

information will not be stored as Freeze Frame data.

Conditions for Clearing the MIL/DTC

DA history DTC P0563 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0563 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

If the DTC sets when an accessory is operated, check for

a poor connection or defective accessory.

DTC P0562 – System Voltage Low

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Using a DVM, measure the battery voltage at the

battery.

Is the battery voltage greater than the specified value? 11.5 V Go to

Step 3

Charge

battery, then

go to

Step 3

31. Install a Tech 2.

2. Select “Ignition Volts” on the Tech 2.

3. Start the engine and raise the engine speed to the

specified value.

4. Load the electrical system by turning on the

headlights, high blower, etc.

Is the ignition voltage approximately equal to the

specified value? 2000 RPM

12.8-14.1 V Go to

Step 4

Go to

Starting/Char

ging

41. Ignition “OFF.”

2. Disconnect the ECM connector at the ECM.

3. Using a DVM, measure the battery voltage at the

ECM connector.

Is it approximately equal to battery voltage? —

Check for

excessive

current draw

with ignition

“OFF,” engine

“OFF.” Go to

Step 5

51. Check for faulty connections at the ECM harness

terminals.

2. Repair as necessary.

Was a repair necessary? — Verify repair Go to

Step 6

6Check for an open battery feed circuit to the ECM.

Is the action complete? — Verify repair Go to

Step 7

7Replace the ECM.

Is the action complete? — Verify repair —

P0563 System Voltage High

Circuit Description

The engine control module (ECM) monitors the system

voltage on the ignition feed terminals to the ECM. A

system voltage DTC will set whenever the voltage is

above a calibrated value.

Conditions for Setting the DTC

DEngine is running.

DSystem voltage is above 16 volts for more than 20

second.

Action Taken When the DTC Sets

DThe ECM will not illuminate the malfunction indicator

lamp (MIL).

DThe ECM will store as Failure Records only conditions

which were present when the DTC was set. This

information will not be stored as Freeze Frame data.

Conditions for Clearing the MIL/DTC

DA history DTC P0563 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0563 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

If the DTC sets when an accessory is operated, check for

a poor connection or defective accessory.

DTC P0563 – System Voltage High

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Using a DVM, measure the battery voltage at the

battery.

Is the battery voltage less than the specified value? 11.5 V Go to

Step 3

Go to

Step 4

31. Charge the battery and clean the battery terminals.

2. Clean the battery ground cable connection if

corrosion is indicated.

Is the battery voltage less than the specified value? 11.5 V Replace

battery Go to

Step 4

41. Turn “OFF” all the accessories.

2. Install a Tech 2.

3. Select the ignition voltage parameter on the Tech 2.

4. Start the engine and raise the engine RPM to the

specified value.

Is the voltage more than 2.5 volts greater than the

measurement taken in step 2 or 3? 2000 RPM

Go to

Starting/Char

ging

Go to

Step 5

5Replace the ECM.

Is the action complete? — Verify repair —

P0601 ECM Memory

Circuit Description

The engine control module (ECM) used in this vehicle

utilizes an electrically erasable programmable read-only

memory (EEPROM). The EEPROM contains program

information and the calibrations required for engine,

transmission, and engine diagnostics operation.

Unlike the PROM used in past applications, the EEPROM

is not replaceable.

Conditions for Setting the DTC

DThe ECM detects an internal program fault (check sum

error).

DIgnition “ON”.

Action Taken When the DTC Sets

DThe ECM will not illuminate the malfunction indicator

lamp (MIL).

DThe ECM will store conditions which were present

when the DTC was set in the Failure Records data only.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P0601 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P0601 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

DDTC P0601 indicates that the contents of the

EEPROM have changed since the ECM was

programmed. The only possible repair is ECM

replacement.

DTC P0601 – ECM Memory

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Replace the ECM.

Is the action complete? — Verify repair —

P1171 Fuel System Lean Dueing Acceleration

060RW053

Circuit Description

The engine control module (ECM) internal circuitry can

identify if the vehicle fuel system is capable of supplying

adequate amounts of fuel during heavy acceleration

(power enrichment). The ECM monitors the voltage of

the oxygen sensor during power enrichment. When a

power enrichment mode of operation is requested during

“closed loop” operation (by heavy acceleration), the ECM

will provide more fuel to the engine. Under these

conditions the ECM should detect a “rich” condition (high

oxygen sensor voltage). If this “rich” exhaust is not

detected at this time, a DTC P1171 will set. A plugged fuel

filter, restricted fuel line, restricted in-tank filter or

defective fuel pump can prevent adequate amouts of fuel

from being supplied during power enrichment mode.

Conditions for Setting the DTC

DNo related DTCs.

DEngine is operating in “closed loop power enrichment”

mode for 3 seconds.

DEngine coolant temperature is between 30°C and

120°C.

DWhile in “power enrichment” mode the oxygen sensor

voltage remains below 250 mV for 20 seconds.

DEngine running speed is between 1000 RPM and 6000

RPM.

DTP sensor voltage reading is above 2000 volts.

DAbove conditions present for at least 10 second.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) the first the fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P1171 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P1171 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

DA restricted fuel filter or fuel line, restricted in-tank filter,

or a defective fuel pomp may supply adequate

amounts of fuel at idle, but may not be able to supply

enough fuel during heavy acceleration.

DWater or alcohol in the fuel may cause low HO2S

voltage during acceleration.

DCheck for faulty or plugged fuel injector(s).

DCheck for low fuel.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

4. When the engine is idling or at steady cruise, the

HO2S voltage should vary from between

approximately 100 mV to 900 mV. It is possible to

measure a satisfactory fuel pressure at idle even

though the pressure may drop at high flow

requirements. It may be necessary to watch fuel

pressure at high engine load.

5. Wrap a shop towel around the fuel pressure

connector to absorb any small amount of fuel

leakage that may occur when installing gauge.

Ignition “ON,” pump pressure should be

280-320kpa.

DTC P1171 – Fuel System Lean During Acceleration

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

2Are any component-related DTCs set?

—

Go to

component

DTC charts Go to

Step 3

31. Check the vehicle’s fuel tank for an adequate

amount of fuel.

2. Add fuel to the vehicle’s fuel tank if the tank is almost

empty.

Was fuel added to the vehicle’s fuel tank? —Go to

Step 4

Go to

Step 5

41. Place the transmission in park.

2. Using a Tech 2, observe HO2S voltage while

running warm engine 75°C-95°C (167°F-203°F) at

1200 RPM.

3. HO2S 1 voltage should vary within the specified

range.

4. Quickly open the throttle halfway for a few seconds.

Did the voltage suddenly rise toward the high end of the

specified range? 100-900 mV

Go to Fuel

System

Electrical Test Go to

Step 5

51. Disconnect the fuel pump relay and crank the

engine to relieve the fuel pressure.

2. Install the fuel pressure gauge.

3. Start the engine and idle at normal operating

temperature.

4. Disconnect the vacuum line going to the fuel

pressure regulator.

With the engine running, is the fuel pressure within the

specified range? 280-325 kpa

(41-46 psi)

Go to

OBD

System

Check

Go to

Step 6

6Check for restricted fuel lines or restricted in-line filter.

Was a problem found? — Verify repair Go to

Step 7

Step NoYesValue(s)Action

71. Ignition “OFF.”

2. Remove the fuel pump relay and replace it with a

fused jumper which will connect the relay’s battery

terminal to the terminal leading to the fuel pump

fuse.

3. While the fuel pump is operating, use pliers to slowly

close the return line (do not exceed the first

specified value).

Using the pliers to restrict the return line, can the fuel

pressure be manipulated to exceed the second

specified value?

414 kpa (60

psi) 325 kpa

(46 psi)

Go to

Diagnostic

Aids

Go to

Step 8

8Check for:

DFaulty fuel pump

DRestricted fuel pump strainer (sock)

DIncorrect fuel pump

DIncorrect fuel being used

DHot fuel

Is the action complete? — Verify repair —

P1508 IAC System Low RPM

060RW076

Circuit Description

The engine control module (ECM) controls engine idle

speed by adjusting the position of the idle air control (IAC)

motor pintle. The IAC is a bi-directional stepper motor

driven by two coils. The ECM applies current to the IAC

coils in steps (counts) to extend the IAC pintle into a

passage in the throttle body to decrease air flow. The

ECM reverses the current to retract the pintle, increasing

air flow. This method allows highly accurate control of idle

speed and quick response to changes in engine load. If

the ECM detects a condition where too low of an idle

speed is present and the ECM is unable to adjust idle

speed by increasing the IAC counts, DTC P1508 will set,

indicating a problem with the idle control system.

Conditions for Setting the DTC

DNo Tech 2 test is being run.

DNone of these DTCs are set: TP sensor, CMP, CKP,

MAF.

DBarometric pressure is above 75 kpa.

DEngine coolant temperature (ECT) is above 75°C.

DIgnition voltage is above 11 volts.

DThe throttle is closed.

DEngine speed is between 1000 RPM and 6000 RPM.

DRelation of IAC step and MAF in wrong.

DAll of the above conditions are met for 1 seconds.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) after the second consecutive trip in which the

fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P1508 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P1508 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM or IAC motor – Inspect

harness connectors for backed-out terminals,

improper mating, broken locks, improperly formed or

damaged terminals, and poor terminal-to-wire

connection.

DDamaged harness – Inspect the wiring for damage.

DRestricted air intake system – Check for a possible

collapsed air intake duct, restricted air filter element,

or foreign objects blocking the air intake system.

DThrottle body – Check for objects blocking the IAC

passage or throttle bore, excessive deposits in the IAC

passage and on the IAC pintle, and excessive deposits

in the throttle bore and on the throttle plate.

DLarge vacuum leak – Check for a condition that causes

a large vacuum leak, such as an incorrectly installed or

faulty PCV valve or a disconnected brake booster

hose.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P1508 –IAC System Low RPM

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Start the engine.

2. Turn all accessories “OFF”(A/C, rear defroster,

etc).

3. Using a T ech 2, command RPM up to 1500, down to

500, and the up to 1500 while monitoring the

“Engine Speed” on the Tech 2.

NOTE: This T ech 2 command may cause the engine to

“cut out” when RPM goes above 1500. If this occurs,

the “cutting out” will stop when the Tech 2 command for

the test is discontinued, or if the Tech 2 command is

changed to less than 1500 RPM.

Does the “Engine Speed” remain within the specified

value of the “Desired Idle” for each RPM command? ± 50 RPM

No trouble

found. Go to

Diagnostic

Aids

Go to

Step 3

31. Disconnect the IAC.

2. Install IAC Node Light J 37027 or equivalent.

3. With the engine running, command RPM up to

1500, down to 500, and then up to 1500 while

observing the node light.

NOTE: This T ech 2 command may cause the engine to

“cut out” when RPM goes above 1500. If this occurs,

the “cutting out” will stop when the Tech 2 command for

the test is discontinued, or if the Tech 2 command is

changed to less than 1500 RPM.

Does each node light cycle red and green (never

“OFF”)? — Go to

Step 5

Go to

Step 4

41. Check the following circuits for an open, short to

voltage, short ground, or poor connections at the

ECM:

DIAC “A” Low.

DIAC “A” High.

DIAC “B” Low.

DIAC “B” High.

2. If a problem its found, repair as necessary,

Was a problem found? — Verify repair Go to

Step 8

Step NoYesValue(s)Action

5Visually/physically inspect for following conditions:

DRestricted air intake system. Check for a possible

collapsed air intake duct, restricted air filter

element, or foreign objects blocking the air intake

system.

DThrottle body . Check for objects blocking the IAC

passage or throttle bore, excessive deposits in

the IAC passage and on the IAC pintle, and

excessive deposits in the throttle bore and on the

throttle plate.

Do any of the above require a repair? —

Refer to

appropriate

section for

on-vehicle

service Go to

Step 6

61. Check for a poor connection at the IAC harness

connector.

2. If a problem is found, replace faulty terminals as

necessary.

Was a problem found? — Verify repair Go to

Step 7

7Replace the IAC valve.

Is the action complete? — Verify repair —

8Replace the ECM.

Is the action complete? — Verify repair —

P1509 IAC System High RPM

060RW076

Circuit Description

The engine control module (ECM) controls engine idle

speed by adjusting the position of the idle air control (IAC)

motor pintle. The IAC is a bi-directional stepper motor

driven by two coils. The ECM applies current to the IAC

coils in steps (counts) to extend the IAC pintle into a

passage in the throttle body to decrease air flow. The

ECM reverses the current to retract the pintle, increasing

air flow. This method allows highly accurate control of idle

speed and quick response to changes in engine load. If

the ECM detect a condition where too high of an idle

speed is present and the ECM is unable to adjust idle

speed by increasing the IAC counts, DTC P1509 will set,

indicating a problem with the idle control system.

Conditions for Setting the DTC

DNo Tech 2 test is being run.

DNone of these DTCs are set: TP sensor, CMP, CKP,

MAF.

DBarometric pressure is above 75 kpa.

DEngine coolant temperature (ECT) is above 75°C.

DIgnition voltage is above 11 volts.

DThe throttle is closed.

DEngine speed is between 1000 RPM and 6000 RPM.

DRelation of IAC step and MAF in wrong.

DAll of the above conditions are met for 1 seconds.

Action Taken When the DTC Sets

DThe ECM will illuminate the malfunction indicator lamp

(MIL) after the second consecutive trip in which the

fault is detected.

DThe ECM will store conditions which were present

when the DTC was set as Freeze Frame and in the

Failure Records data.

Conditions for Clearing the MIL/DTC

DThe ECM will turn the MIL “OFF” on the third

consecutive trip cycle during which the diagnostic has

been run and the fault condition is no longer present.

DA history DTC P1509 will clear after 40 consecutive

warm-up cycles have occurred without a fault.

DDTC P1509 can be cleared by using the Tech 2 “Clear

Info” function or by disconnecting the ECM battery

feed.

Diagnostic Aids

Check for the following conditions:

DPoor connection at ECM or IAC motor – Inspect

harness connectors for backed-out terminals,

improper mating, broken locks, improperly formed or

damaged terminals, and poor terminal-to-wire

connection.

DDamaged harness – Inspect the wiring for damage.

DVacuum leak – Check for a condition that causes a

vacuum leak, such as disconnected or damaged

hoses, leaks at the EGR valve and the EGR pipe to the

intake manifold, leaks at the throttle body, faulty or

incorrectly installed PCV valve, leaks at the intake

manifold, etc.

DThrottle body – Check for sticking throttle plate. Also

inspect the IAC passage for deposits or objects which

keep the IAC pintle from fully extending.

Reviewing the Failure Records vehicle mileage since the

diagnostic test last failed may help determine how often

the condition that caused the DTC to be set occurs. This

may assist in diagnosing the condition.

DTC P1509 –IAC System High RPM

Step Action Value(s) YesNo

1Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Start the engine.

2. Turn all accessories “OFF” (A/C, rear defroster,

etc.).

3. Using a T ech 2, command RPM up to 1500, down to

500, and then up to 1500 while monitoring “Engine

Speed” on the Tech 2.

NOTE: This T ech 2 command may cause the engine to

“cut out” when RPM goes above 1500. If this occurs,

the “cutting out” will stop when the Tech 2 command for

the test is discontinued, or if the Tech 2 command is

changed to less than 1500 RPM.

Does the “Engine Speed” remain within the specified

value of “Desired Idle” for each RPM command? ± 50 RPM

No trouble

found. Go to

Diagnostic

Aids

Go to

Step 3

31. Disconnect the IAC.

2. Install IAC Node Light J 37027 or equivalent.

3. With the engine running, command RPM up to

1500, down to 500, and then up to 1500 while

observing the node light.

NOTE: This T ech 2 command may cause the engine to

“cut out” when RPM goes above 1500. If this occurs,

the “cutting out” will stop when the Tech 2 command for

the test is discontinued, or if the Tech 2 command is

changed to less than 1500 RPM.

Does each node light cycle red and green (never

“OFF”)? — Go to

Step 5

Go to

Step 4

41. Check the following circuits for an open, short to

voltage, short ground, or poor connections at the

ECM:

DIAC “A” Low.

DIAC “A” High.

DIAC “B” Low.

DIAC “B” High.

2. If a problem its found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 8

5Visually/physically inspect for the following conditions:

DVacuum leaks.

DThrottle plate or throttle shaft for binding.

DAccelerator and cruise control cables for being

misadjusted or for binding.

DFaulty, missing, or incorrectly installed PCV

valve.

Do any of the above require a repair? —

Refer to

appropriate

section for

on-vehicle

service Go to

Step 6

Step NoYesValue(s)Action

61. Check for a poor connection at the IAC harness

connector.

2. If a problem is found, replace faulty terminals as

necessary.

Was a problem found? — Verify repair Go to

Step 7

7Replace the IAC valve.

Is the action complete? — Verify repair —

8Replace the ECM.

Is the action complete? — Verify repair —

P1626 - No Response From Immobiliser

060RA00003

Circuit Description

An encrypted signal is transmitted from the Immobiliser

Control Unit to the ECM when the ignition is turned ON.

Condition for Setting the DTC

A DTC 1626 will be set when:

• No there is no signal transmission from the ICU to

the ECM within 0.5 seconds of turning the ignition

ON.

Action Taken When the DTC sets

• Rapid flashing of the MIL (“CHECK ENGINE” lamp).

• The Engine does not start.

Condition for Clearing the MIL/DTC

• Clear DTC information with TECH 2. Refer to Section

0C TECH 2 Diagnosis

Diagnostic Aids

Check for the following conditions:

• Poor connection at ECM and Immobiliser Inspect

harness connectors for backed out terminals,

improper mating, broken locks, improperly formed or

damaged terminals, and poor terminal to wire

connection.

• Damaged harness-Inspect the wiring harness for

damage, If the harness appears to be OK, disconnect

the ECM and Immobiliser, turn the ignition “ON" and

observe a voltmeter connected to the suspect driver

circuit at the ECM and Immobiliser harness

connector while moving connectors and wiring

harnesses relates to the MIL. A change in voltage will

indicate the location of the fault.

DTC P1626-No Response From Immobiliser

Step Action Value(s) Yes No

1 Was the “On-Board Diagnostic (OBD) system Check"

performed? — Go to Step 2 Go to OBD

system check

2 Using the Tech2 system selection menu, select ‘Body

- Immobiliser - DTC’ function.

Does the Tech2 display B**** appear?

—

Refer to

Section11A

“Engine

Immobiliser

System" Go to Step 3

3 Does the Tech2 display DTC P1626 appear? — Go to Step 4Refer to

Diagnostic Aids

4 Check the ECM and ICU harness and connectors for:

1. Backed out terminals, improper mating, broken

locks, improperly formed or damaged terminals,

and poor terminal to wire connection.

2. Damaged harness - Inspect the wiring harness for

damage.

If a problem found, repair as necessary.

Was a problem found? Verify repair Go to Step 5

5 1. Disconnect the Vehicle Speed Sensor line VSS

OUT harness.

2. Check for an open circuit or short voltage between

ICU Pin No.8 and ECM Pin No.B-32 by DMM.

If a problem found, repair as necessary.

Was a problem found? — Verify repair Go to Step 5

6 Replace the ECM.

Important: Refer to Section 11A - Engine

Immobiliser System for the Immobiliser Programming

procedure.

Important: Ensure the latest software program is

downloaded to the ECM.

Is the action complete? — Verify repair —

P1631 - Received response was not correct

060RA00003

Circuit Description

An encrypted signal is transmitted from the Immobiliser

Control Unit to the ECM when the ignition is turned ON.

Condition for Setting the DTC

A DTC 1631 will be set when:

• An incorrect signal is transmitted from the ICU to the

ECM within 0.5 seconds of turning the ignition ON.

Action Taken When the DTC Sets

• Rapid flashing of the MIL (“CHECK ENGINE” lamp).

• The Engine does not start.

Condition for Clearing the MIL/DTC

• Clear DTC information with TECH 2. Refer to

Section 0C TECH 2 Diagnosis

Diagnostic Aids

Check for the following conditions:

• Poor connection at ECM and Immobiliser. Inspect

harness connectors for backed out terminals,

improper mating, broken locks, improperly for med or

damaged terminals, and poor terminal to wire

connection.

• Damaged harness-Inspect the wiring harness for

damage, If the harness appears to be OK, disconnect

the ECM and Immobiliser, tur n the ignition “ON" and

observe a voltmeter connected to the suspect driver

circuit at the ECM and Immobiliser harness

connector while moving connectors and wiring

harnesses relates to the MIL. A change in voltage will

indicate the location of the fault.

DTC P1631 Received response was not correct

Step Action Value(s) Yes No

1 Was the “On-Board Diagnostic (OBD) system Check"

performed? — Go to Step 2 Go to OBD

system check

2 Check the ECM and ICU harness and connectors for:

1. Backed out terminals, improper mating, broken

locks, improperly formed or damaged terminals,

and poor terminal to wire connection.

2. Damaged harness - Inspect the wiring harness for

damage.

If a problem found, repair as necessary.

Was a problem found? Verify repair Go to Step 3

3 Replace the ECM.

Important: Refer to Section 11A - Engine

Immobiliser System for the Immobiliser Programming

procedure.

Important: Ensure the latest software program is

downloaded to the ECM.

Is the action complete? — Verify repair —

P1648 Received incorrect security code

060RA00003

Circuit Description

A security code is transmitted from the ICU to the ECM

immediately the ignition is turned ON.

Condition for Setting the DTC

A DTC 1648 will be set when:

• The incorrect security code is transmitted from the

ICU to the ECM.

Action Taken When the DTC Sets

• Rapid flashing of the MIL (“CHECK ENGINE” lamp).

• The Engine does not start.

Condition for Clearing the MIL/DTC

• Clear DTC information with TECH 2. Refer to

Section 0C TECH 2 Diagnosis

Diagnostic Aids

Check for the following conditions:

• Poor connection at ECM and Immobiliser. Inspect

harness connectors for backed out terminals,

improper mating, broken locks, improperly for med or

damaged terminals, and poor terminal to wire

connection.

• Damaged harness-Inspect the wiring harness for

damage, If the harness appears to be OK, disconnect

the ECM and Immobiliser, tur n the ignition “ON" and

observe a voltmeter connected to the suspect driver

circuit at the ECM and Immobiliser harness

connector while moving connectors and wiring

harnesses relates to the MIL. A change in voltage will

indicate the location of the fault.

DTC P1648-Received incorrect security code

Step Action Value(s) Yes No

1 Was the “On-Board Diagnostic (OBD) system Check"

performed? — Go to Step 2 Go to OBD

system check

2 Check the ECM and ICU harness and connectors for:

1. Backed out terminals, improper mating, broken

locks, improperly formed or damaged terminals,

and poor terminal to wire connection.

2. Damaged harness - Inspect the wiring harness for

damage.

If a problem found, repair as necessary.

Was a problem found? Verify repair Go to Step 3

3 Rech eck the secur ity code.

Is the action complete? — Verify repair —

P1649 Security Code & Security Key Not Programmed

060RA00003

Circuit Description

The ECM is programmed with security code information

during installation

Condition for Setting the DTC

A DTC 1649 will be set when:

• The Security code & the transponder key not

programmed into the ECM.

Action Taken When the DTC Sets

• Rapid flashing of the MIL (“CHECK ENGINE” lamp).

• The Engine does not start.

In case replacement ECM/ECM, Action

Taken When the DTC Sets

• Rapid flashing of the MIL (“CHECK ENGINE” lamp).

• The Engine does not start.

Condition for Clearing the MIL/DTC

• Clear DTC information with TECH 2. Refer to

Section 0C TECH 2 Diagnosis

Diagnostic Aids

Check for the following conditions:

• Poor connection at ECM and Immobiliser. Inspect

harness connectors for backed out terminals,

improper mating, broken locks, improperly for med or

damaged terminals, and poor terminal to wire

connection.

• Damaged harness-Inspect the wiring harness for

damage, If the harness appears to be OK, disconnect

the ECM and Immobiliser, tur n the ignition “ON" and

observe a voltmeter connected to the suspect driver

circuit at the ECM and Immobiliser harness

connector while moving connectors and wiring

harnesses relates to the MIL.

A change in voltage will indicate the location of the

fault.

DTC P1649 Security code & secret key not programmed

Step Action Value(s) Yes No

1 Was the “On-Board Diagnostic (OBD) system Check"

performed? — Go to Step 2 Go to OBD

system check

2 Using the Tech2 system selection menu, select Body

function.

Does the Tech2 display B**** appear?

—

Refer to

Section11A

“Engine

Immobiliser

System" Go to Step 3

3 Replace the ECM.

Important: Refer to Section 11A - Engine

Immobiliser System for the Immobiliser Programming

procedure.

Important: Ensure the latest software program is

downloaded to the ECM.

Is the action complete? — Go to Step 4 —

4 Does the Tech2 display P1649 appear? — Go to Step 3 Verify repair

Symptom Diagnosis

Surges and/or Chuggles Symptom

Step Action Value(s) YesNo

1DEFINITION:

Engine power variation under steady throttle or cruise.

Feels like the vehicle speeds up and slows down with

no change in the accelerator pedal.

Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Perform a bulletin search.

2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom? — Verify repair Go to

Step 3

3Was a visual/physical check performed?

—Go to

Step 4

Go to

Visual/Physic

al Check

4Be sure that the driver understands transmission

torque converter clutch and A/C compressor operation

as explained in the owner’s manual.

Inform the customer how the TCC and the A/C clutch

operate.

Is the customer experiencing a normal condition? —System OK Go to

Step 5

51. Check the the fuel control heated oxygen sensors

(HO2S). The fuel control heated oxygen sensors

(HO2S) should respond quickly to different throttle

positions. If they don’t, check them for silicon or

other contaminants from fuel or use of improper

RTV sealant. The sensors may have a white

powdery coating.

Silicon contamination causes a high but false

HO2S signal voltage (rich exhaust indication).

The ECM will then reduce the amount of fuel

delivered to the engine, causing a severe

driveability problem. For more information, refer

Engine Control Module (ECM) and Sensors

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 6

61. Check the fuel pressure. Refer to

Fuel System

Pressure Test

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 7

7Monitor the long term fuel trim on the Tech 2.

Is the long term fuel trim significantly in the negative

range (rich condition)? —Go to

Step 8

Go to

Step 9

81. Check items that can cause the engine to run rich.

Refer to

Diagnostic Aids

DTC P0172 Diagnostic

Support

2. If a problem is found, repair as necessary.

Was a problem found? —Go to

Step 10

Verify repair

Step NoYesValue(s)Action

91. Check items that can cause the engine to run lean.

Refer to

Diagnostic Aids

DTC P0171

2. If a problem is found, repair as necessary.

Was a problem found? —Go to

Step 10

Verify repair

10 1. Check for proper ignition voltage output with spark

tester J 26792 (ST-125). Refer to

Electric Ignition

System

for procedure.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 11

11 1. Check for a loose ignition coil ground.

Refer to

Electric Ignition System

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 12

12 1. Check the ignition coils for cracks or carbon

tracking.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 14

13 1. Remove the spark plugs and check for wet plugs,

cracks, wear, improper gap, burned electrodes, or

heavy deposits. Refer to

Electronic Ignition

System

NOTE: If spark plugs are gas or oil fouled, the cause of

the fouling must be determined before replacing the

spark plugs.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 14

14 1. Check the injector connections.

2. If any of the injector connectors are connected to an

incorrect cylinder, correct as necessary.

Was a problem found? — Verify repair Go to

Step 15

15 1. Check ECM grounds for the cleanliness, tightness

and proper locations. Refer to the ECM wiring

diagrams in

Electrical Diagnosis

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 16

16 1. Check MAF sensor connections.

2. If a problem is found, replace the faulty terminals as

necessary. Refer to

Electrical Diagnosis

for wiring

repair procedures.

Was a problem found? — Verify repair Go to

Step 17

17 1. Visually/physically check vacuum hoses for splits,

kinks, and proper connections and routing as

shown on the “Vehicle Emission Control

Information” label.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 18

Step NoYesValue(s)Action

18 1. Check the exhaust system for possible restriction:

DInspect the exhaust system for damaged or

collapsed pipes.

DInspect the muffler for heat distress or possible

internal failure.

DCheck for a possible plugged three-way

catalytic converter by checking the exhaust

system back pressure. Refer to

Restricted

Exhaust System Check

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 19

19 1. Review all diagnostic procedures within this table.

2. If all procedures have been completed and no

malfunctions have been found, review/inspect the

following:

DVisual/physical inspection

DTech 2 data

DFreeze Frame data/Failure Records buffer

DAll electrical connections within a suspected

circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair

Contact

Technical

Assistance

Lack of Power, Sluggish or Spongy Symptom

Step Action Value(s) YesNo

1DEFINITION:

Engine delivers less than expected power. Little or no

increase in speed when accelerator pedal is pushed

down part-way.

Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Perform a bulletin search.

2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom? — Verify repair Go to

Step 3

3Was a visual/physical check performed?

—Go to

Step 4

Go to

Visual/Physic

al Check

41. Remove and check the air filter element for dirt or

restrictions. Refer to

Air Intake System

On-Vehicle Service

2. Replace the air filter element if necessary.

Was a repair required? — Verify repair Go to

Step 5

51. Check for low fuel pressure. Refer to

Fuel System

Pressure Test

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 6

61. Check for water-or alcohol-contaminated fuel.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 7

71. Using a Tech 2, monitor the knock sensor (KS)

system for excessive spark retard activity. Refer to

Knock Sensor (KS) System

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 8

81. Check for proper ignition voltage output with spark

tester 5-8840-0383-0. Refer to

Electronic Ignition

System

for procedure.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 9

91. Remove the spark plugs and check for wet plugs,

cracks, wear, improper gap, burned electrodes, or

heavy deposits. Refer to

Electronic Ignition

System

NOTE: If spark plugs are gas or oil fouled, the cause of

the fouling must be determined before replacing the

spark plugs.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 10

10 1. Check the ignition coils for cracks or carbon

tracking.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 11

Step NoYesValue(s)Action

11 1. Check the ECM grounds for the cleanliness,

tightness and proper locations. Refer to the ECM

wiring diagrams in

Electrical Diagnosis

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 12

12 1. Check the exhaust system for possible restriction:

DInspect the exhaust system for damaged or

collapsed pipes.

DInspect the muffler for heat distress or possible

internal failure.

DCheck for a possible plugged three-way

catalytic converter by checking the exhaust

system back pressure. Refer to

Restricted

Exhaust System Check

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 13

13 1. Check the torque converter clutch (TCC) for proper

operation. Refer to

Transmission Diagnosis

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 14

14 1. Check for an engine mechanical problem. Check

for low compression, incorrect or worn camshaft,

loose timing belt, etc. Refer to

Engine Mechanical

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 15

15 1. Review all diagnostic procedures within this table.

2. If all procedures have been completed and no

malfunctions have been found, review/inspect the

following:

DVisual/physical inspection

DTech 2 data

DFreeze Frame data/Failure Records buffer

DAll electrical connections within a suspected

circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair

Contact

Technical

Assistance

Detonation/Spark Knock Symptom

Step Action Value(s) YesNo

1DEFINITION:

A mild to severe ping, usually worse under acceleration.

The engine makes sharp metallic knocks that change

with throttle opening.

Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Perform a bulletin search.

2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom? — Verify repair Go to

Step 3

3Was a visual/physical check performed?

—Go to

Step 4

Go to

Visual/Physic

al Check

4If Tech 2 readings are normal (refer to

Typical Scan

Values

) and there are no engine mechanical faults, fill

the fuel tank with a known quality gasoline that has a

minimum octane rating of 87 and re-evaluate the

vehicle performance.

Is detonation present? —Go to

Step 5

Verify repair

51. Check the transmission range switch circuit. Use a

Tech 2 and be sure the Tech 2 indicates that the

vehicle is in drive with the gear selector in drive or

overdrive.

2. If a problem is found, diagnose and repair the

transmission range switch as necessary.

Was a problem found? — Verify repair Go to

Step 6

61. Check TCC operation.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 7

71. Check for obvious overheating problems:

DLow engine coolant.

DRestricted air flow to radiator, or restricted

water flow through radiator.

DCorrect coolant solution should be a 50/50 mix

of approved antifreeze/coolant and water.

Refer to

Engine Cooling

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 8

81. Check fuel pressure. Refer to

Fuel System

Pressure Test

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 9

91. Check items that can cause an engine to run lean

(long term fuel trim significantly in the positive

range). For a lean condition, refer to

Diagnostic

Aids

DTC P0171 Diagnostic Support

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 10

Step NoYesValue(s)Action

10 1. Spark plugs for proper heat range. Refer to

General

Information

2. If incorrect spark plugs are installed, replace spark

plugs as necessary.

Did any spark plugs require replacement? — Verify repair Go to

Step 11

11 1. Remove excessive carbon buildup with a top engine

cleaner. Refer to instructions on the top engine

cleaner can.

2. Re-evaluate vehicle performance.

Is detonation still present? —Go to

Step 12

Verify repair

12 1. Check for an engine mechanical problem. Perform

a cylinder compression check. Refer to

Engine

Mechanical

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 13

13 1. Review all diagnostic procedures within this table.

2. If all procedures have been completed and no

malfunctions have been found, review/inspect the

following:

DVisual/physical inspection

DTech 2 data

DFreeze Frame data/Failure Records buffer

DAll electrical connections within a suspected

circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair

Contact

Technical

Assistance

Rough, Unstable, or Incorrect Idle, Stalling Symptom

Step Action Value(s) YesNo

1DEFINITION:

Engine runs unevenly at idle. If severe, the engine or

vehicle may shake. Engine idle speed may vary in

RPM. Either condition may be severe enough to stall

the engine.

Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Perform a bulletin search.

2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom? —Go to

Step 13

Go to

Step 3

3Was a visual/physical check performed?

—Go to

Step 4

Go to

Visual/Physic

al Check

41. Check the ECM grounds for cleanliness, tightness

and proper routing. Refer to the ECM wiring

diagrams in

Electrical Diagnosis

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 5

5Observe the long term fuel trim on the Tech 2.

Is the long term fuel trim significantly in the negative

range (rich condition)? —Go to

Step 6

Go to

Step 7

61. Check items that can cause the engine to run rich.

Refer to

Diagnostic Aids

DTC P0172 Diagnostic

Support

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 9

7Is the long term fuel trim significantly in the positive

range (lean condition)? —Go to

Step 8

Go to

Step 9

81. Check items that can cause the engine to run lean.

Refer to

Diagnostic Aids

DTC P0171 Diagnostic

Support

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 9

91. Check for incorrect idle speed. Ensure that the

following conditions are present:

DThe engine is fully warm.

DThe accessories are “OFF.”

2. Using a Tech 2, monitor the IAC position.

Is the IAC position within the specified values?

Between 10

and 50

counts Go to

Step 11

Go to

Step 10

Step NoYesValue(s)Action

10 1. Visually/physically inspect for the following

conditions:

DRestricted air intake system. Check for a

possible collapsed air intake duct, restricted

air filter element, or foreign objects blocking

the air intake system.

DThrottle body. Check for objects blocking the

IAC passage or throttle bore, excessive

deposits in the IAC passage and on the IAC

pintle, and excessive deposits in the throttle

bore and on the throttle plate.

DLarge vacuum leak. Check for a condition that

causes a large vacuum leak, such as an

incorrectly installed or faulty crankcase

ventilation valve or a disconnected brake

booster hose.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 8

11 Check the injector connections. If any of the injectors

are connected to an incorrect cylinder, correct as

necessary.

Was a problem found? — Verify repair Go to

Step 12

12 1. Perform the “Injector Coil/Balance Test” in

Fuel

Metering System

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 13

13 1. Check for fuel in the pressure regulator vacuum

hose.

2. If fuel is present, replace the fuel pressure regulator

assembly. Refer to

Fuel Metering System

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 14

14 1. Check for proper ignition voltage output with spark

tester J 26792 (ST-125). Refer to

Electronic Ignition

System

for the procedure.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 15

15 1. Remove spark plugs. Check for wet plugs, cracks,

wear, improper gap, burned electrodes, or heavy

deposits. Refer to

Electronic Ignition System

NOTE: If spark plugs are gas or oil fouled, the cause of

the fouling must be determined before replacing the

spark plugs.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 16

16 1. Check for a loose ignition coil ground.

Refer to

Electrical Ignition System

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 17

Step NoYesValue(s)Action

17 1. Check ignition coils for cracks or carbon tracking.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 18

18 Using a Tech 2, monitor the throttle position (TP) angle

with the engine idling.

Is the TP angle at the specified value and steady? 0% Go to

Step 19

Refer to

DTC

P0123

for

further

diagnosis

19 1. Check the positive crankcase ventilation (PCV)

valve for proper operation. Refer to

Crankcase

Ventilation System

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 20

20 1. Check the transmission range switch circuit. Use a

Tech 2 and be sure the Tech 2 indicates that the

vehicle is in drive with the gear selector in drive or

overdrive.

2. If a problem is found, diagnose and repair the

transmission range switch as necessary (refer to

4L30-E Automatic Transmission Diagnosis

Was a problem found? — Verify repair Go to

Step 21

21 1. Check for the following engine mechanical items.

Refer to

Engine Mechanical

for diagnosis

procedures:

DLow compression

DSticking or leaking valves

DWorn camshaft lobe(s)

DCamshaft drive belt slipped or stripped

DIncorrect valve timing

DWorn rocker arms

DBroken valve springs

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 22

22 1. Check for faulty motor mounts. Refer to

Engine

Mechanical

for inspection of mounts.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 23

23 1. Review all diagnostic procedures within this table.

2. If all procedures have been completed and no

malfunctions have been found, review/inspect the

following:

DVisual/physical inspection

DTech 2 data

DFreeze Frame data/Failure Records buffer

DAll electrical connections within a suspected

circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair

Contact

Technical

Assistance

Poor Fuel Economy Symptom

Step Action Value(s) YesNo

1DEFINITION:

Fuel economy, as measured by an actual road test, is

noticeably lower than expected. Also, economy is

noticeably lower than it was on this vehicle at one time,

as previously shown by an actual road test. (Larger than

standard tires will cause odometer readings to be

incorrect, and that may cause fuel economy to appear

poor when it is actually normal.)

Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Perform a bulletin search.

2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom? — Verify repair Go to

Step 3

3Was a visual/physical check performed?

—Go to

Step 4

Go to

Visual/Physic

al Check

4Check owner’s driving habits.

DIs the A/C “ON” full time (defroster mode “ON”)?

DAre tires at the correct pressure?

DAre excessively heavy loads being carried?

DIs acceleration too much, too often?

Was a problem found? —Go to

Step 5

Go to

Step 6

5Review the items in Step 4 with the customer and

advise as necessary.

Is the action complete? —System OK —

61. Visually/physically check: V acuum hoses for splits,

kinks, and improper connections and routing as

shown on the “Vehicle Emission Control

Information” label.

2. If a problem is found, repair as necessary.

Was a repair required? — Verify repair Go to

Step 7

71. Remove and check the air filter element for dirt or for

restrictions. Refer to

Air Intake System

2. Replace the air filter element if necessary.

Was a repair required? — Verify repair Go to

Step 8

81. Remove spark plugs and check for wet plugs,

cracks, wear, improper gap, burned electrodes, or

heavy deposits. Refer to

Spark Plug Replacement

NOTE: If spark plugs are gas or oil fouled, the cause of

the fouling must be determined before replacing the

spark plugs.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 9

91. Check for low engine coolant level. Refer to

Engine

Cooling

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 10

Step NoYesValue(s)Action

10 1. Check for an incorrect or faulty engine thermostat.

Refer to

Engine Cooling

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 11

11 1. Check for low engine compression. Refer to

Engine

Mechanical

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 12

12 1. Check the TCC operation. Refer to

Transmission

Diagnosis

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 13

13 1. Check the exhaust system for possible restriction:

DInspect the exhaust system for damaged or

collapsed pipes.

DInspect the muffler for heat distress or possible

internal failure.

DCheck for a possible plugged three-way

catalytic converter by checking the exhaust

system back pressure. Refer to

Restricted

Exhaust System Check

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 14

14 Check for proper calibration of the speedometer.

Does the speed indicated on the speedometer closely

match the vehicle speed displayed on the Tech 2? —Go to

Step 16

Go to

Step 15

15 Diagnose and repair an inaccurate speedometer

condition as necessary. Refer to

Vehicle Speed

Sensor

Electrical Diagnosis

Was a problem found? — Verify repair —

16 1. Check the air intake system and the crankcase for

air leaks. Refer to

Air Intake System

and

Crankcase Ventilation System

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 17

17 1. Review all diagnostic procedures within this table.

2. When all procedures have been completed and no

malfunctions have been found, review/inspect the

following:

DVisual/physical inspection

DTech 2 data

DFreeze Frame data/Failure Records buffer

DAll connections within a suspected circuit

and/or system.

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 18

18 Perform the procedure in

Fuel System Pressure Test

Was the fuel pressure normal? —

Contact

Technical

Assistance Verify repair

Excessive Exhaust Emissions or Odors Symptom

Step Action Value(s) YesNo

1DEFINITION:

Vehicle fails an emission test. Vehicle has excessive

“rotten egg” smell. (Excessive odors do not necessarily

indicate excessive emissions.)

Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Perform a bulletin search.

2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom? —Go to

Step 13

Go to

Step 3

3Was a thorough visual/physical check performed?

—Go to

Step 4

Go to

Visual/Physic

al Check

41. Check for vacuum leaks. Check vacuum lines,

intake manifold, throttle body, etc.

2. If a problem is found, repair as necessary.

Were any vacuum leaks located? —Go to

Step 13

Go to

Step 5

51. Check the fuel cap for proper installation.

2. Secure the fuel cap if necessary.

Was the fuel cap installed properly? —Go to

Step 6

Go to

Step 13

61. Check the fuel pressure. Perform the procedure in

Fuel System Pressure Test

2. If a problem is found, repair as necessary.

Was a problem found? —Go to

Step 13

Go to

Step 7

71. Check for a faulty, plugged, or incorrectly installed

crankcase ventilation valve; also check the

crankcase ventilation system for plugging.

2. If a problem is found, repair as necessary.

Was a problem found? —Go to

Step 13

Go to

Step 8

81. Check the injector connections.

2. If any of the injectors are connected to an incorrect

cylinder, correct as necessary.

Was a problem found? —Go to

Step 13

Go to

Step 9

91. Perform the “Injector Coil/Balance Test” in

Fuel

Metering System

2. If a problem is found, repair as necessary.

Was a problem found? —Go to

Step 13

Go to

Step 10

10 1. Refer to

Engine Cooling

for cooling system

diagnosis.

2. If a problem is found, repair as necessary.

Was a problem found? —Go to

Step 13

Go to

Step 11

11 1. Check EVAP canister for fuel loading. Refer to

Evaporative Emission Control System

2. If a problem is found, repair as necessary.

Was a problem found? —Go to

Step 13

Go to

Step 12

Step NoYesValue(s)Action

12 1. Remove excessive carbon buildup with a top engine

cleaner . Refer to the instructions on the top engine

cleaner can.

2. Perform the exhaust emission test.

Does the vehicle pass the test? —System OK Go to

Step 14

13 Perform the exhaust emission test.

Does the vehicle pass the test? —System OK Go to

Step 14

14 Does the exhaust emission test indicate excessive CO

and HC levels or is long term fuel trim significantly in the

negative range (rich condition)? —Go to

Step 15

Go to

Step 16

15 1. Check items that can cause the engine to run rich.

Refer to

Diagnostic Aids

DTC P0172 Diagnostic

Support

. Make any necessary repairs.

2. Perform the exhaust emission test.

Does the vehicle pass the test? —System OK Go to

Step 17

16 1. Check items that can cause the engine to run lean.

Refer to

Diagnostic Aids

DTC P0171 Diagnostic

Support

. Make any necessary repairs.

2. Perform the exhaust emission test.

Does the vehicle pass the test? —System OK Go to

Step 17

17 1. If a problem is found, repair as necessary.

Was a problem found? —Go to

Step 13

Go to

Step 18

18 1. Check for an engine mechanical problem.

Perform a cylinder compression check (refer to

Engine Mechanical

2. If a problem is found, repair as necessary.

Was a problem found? —Go to

Step 13

Go to

Step 19

19 1. Review all diagnostic procedures within this table.

2. If all procedures have been completed and no

malfunctions have been found, review/inspect the

following:

DVisual/physical inspection

DTech 2 data

DFreeze Frame data/Failure Records butter

DAll electrical connections within a suspected

circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair

Contact

Technical

Assistance

Dieseling, Run-On Symptom

Step Action Value(s) YesNo

1DEFINITION:

Engine continues to run after key is turned “OFF,” but

runs very rough. If engine runs smooth, check ignition

switch and adjustment.

Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Perform a bulletin search.

2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom? — Verify repair Go to

Step 3

3Was a visual/physical check performed?

—Go to

Step 4

Go to

Visual/Physic

al Check

41. Check for a short between B+ and any of the ignition

feed circuits.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 5

51. Review all diagnostic procedures within this table.

2. If all procedures have been completed and no

malfunctions have been found, review/inspect the

following:

DVisual/physical inspection

DTech 2 data

DFreeze Frame data/Failure Records butter

DAll electrical connections within a suspected

circuit and/or system

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair

Contact

Technical

Assistance

Backfire Symptom

Step Action Value(s) YesNo

1DEFINITION:

Fuel ignites in the intake manifold, or in the exhaust

system, making a loud popping noise.

Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Perform a bulletin search.

2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom? — Verify repair Go to

Step 3

3Was a visual/physical check performed?

—Go to

Step 4

Go to

Visual/Physic

al Check

41. Check for proper ignition voltage coil output with

spark tester 5-8840-0383-0. Refer to

Electronic

Ignition System

for procedure.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 5

51. Remove spark plugs and check for wet plugs,

cracks, wear, improper gap, burned electrodes, or

heavy deposits. Refer to

Electronic Ignition

System

NOTE: If spark plugs are gas or oil fouled, the cause of

the fouling must be determined before replacing the

spark plugs. Refer to

DTC P0172

to determine the

cause of a rich condition or

Engine Mechanical

for an oil

fouling condition.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 6

61. Visually/physically inspect the ignition coils for

cracks.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 7

71. Check for an intermittent ignition system

malfunction:

DIntermittent CKP signal.

DIntermittent ignition feed circuit or sensor

ground circuit to the crankshaft position

sensor.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 8

81. Check the fuel pressure. Refer to

Fuel System

Pressure Test

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 9

Step NoYesValue(s)Action

91. Check for the following engine mechanical

conditions.

Refer to

Engine Mechanical

for diagnosis

procedures:

DLow compression

DSticking or leaking valves

DWorn camshaft lobe(s)

DCamshaft drive belt slipped or stripped

DIncorrect valve timing

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 10

10 1. Check the intake and exhaust manifold(s) for

casting flash. Refer to

Engine Mechanical

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 11

11 1. Review all diagnostic procedures within this table.

2. If all procedures have been completed and no

malfunctions have been found, review/inspect the

following:

DVisual/physical inspection

DTech 2 data

DFreeze Frame data/Failure Records butter

DAll electrical connections within a suspected

circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair

Contact

Technical

Assistance

Cuts Out, Misses Symptom

Step Action Value(s) YesNo

1DEFINITION:

Steady pulsation or jerking that follows engine speed;

usually more pronounced as engine load increases.

Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Perform a bulletin search.

2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom? —Go to

Step 13

Go to

Step 3

3Was a visual/physical check performed?

—Go to

Step 4

Go to

Visual/Physic

al Check

41. Check the ECM grounds for clearness, tightness

and proper routing. Refer to the ECM wiring

diagrams in

Electrical Diagnosis

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 5

5Observe the long term fuel trim on the Tech 2.

Is the long term fuel trim significantly in the negative

range (rich condition)? —Go to

Step 6

Go to

Step 7

61. Check items that can cause the engine to run rich.

Refer to

Diagnostic Aids

DTC P0172 Diagnostic

Support

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 9

7Is the long term fuel trim significantly in the positive

range (lean condition)? —Go to

Step 8

Go to

Step 9

81. Check items that can cause the engine to run lean.

Refer to

Diagnostic Aids

DTC P0171 Diagnostic

Support

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 9

91. Check for incorrect idle speed. Ensure that the

following conditions are present:

DThe engine is fully warm.

DThe accessories are “off.”

2. Using a Tech 2, monitor the IAC position.

Is the IAC position within the specified values?

Between 5

and 50

counts Go to

Step 11

Go to

Step 10

Step NoYesValue(s)Action

10 1. Visually/physically inspect for the following

conditions:

DRestricted air intake system. Check for a

possible collapsed air intake duct, restricted

air filter element, or foreign objects blocking

the air intake system.

DThrottle body. Check for objects blocking the

IAC passage or throttle bore, excessive

deposits in the IAC passage and on the IAC

pintle, and excessive deposits in the throttle

bore and on the throttle plate.

DLarge vacuum leak. Check for a condition that

causes a large vacuum leak, such as an

incorrectly installed or faulty PCV valve or

brake booster hose disconnected .

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 8

11 Check the injector connections. If any of the injectors

are connected to an incorrect cylinder, correct as

necessary.

Was a problem found? — Verify repair Go to

Step 12

12 1. Perform the “Injector Coil/Balance Test” in

Fuel

Metering System

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 13

13 1. Check for fuel in the pressure regulator vacuum

hose.

2. If fuel is present, replace the fuel pressure regulator

assembly. Refer to

Fuel Metering System

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 14

14 1. Check for proper ignition voltage output with spark

tester 5-8840-0383-0. Refer to

Electronic Ignition

System

for the procedure.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 15

15 1. Remove spark plugs. Check for wet plugs, cracks,

wear, improper gap, burned electrodes, or heavy

deposits. Refer to

Electronic Ignition System

NOTE: If spark plugs are gas or oil fouled, the cause of

the fouling must be determined before replacing the

spark plugs.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 16

16 1. Check for a loose ignition coil ground.

Refer to

Electronic Ignition System

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 17

Step NoYesValue(s)Action

17 1. Check ignition coils for cracks or carbon tracking.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 18

18 Using a Tech 2, monitor the TP angle with the engine

idling.

Is the TP angle at the specified value and steady? 0% Go to

Step 19

Refer to

DTC

P0123

for

further

diagnosis

19 1. Check the PCV valve for proper operation. Refer to

Crankcase Ventilation System

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 20

20 1. Check the transmission range switch circuit. Use a

Tech 2 and be sure the Tech 2 indicates that the

vehicle is in drive with the gear selector in drive or

overdrive.

2. If a problem is found, diagnose and repair the

transmission range switch as necessary.

Was a problem found? — Verify repair Go to

Step 21

21 1. Check the following engine mechanical items.

Refer to

Engine Mechanical

for diagnosis

procedures:

DLow compression

DSticking or leaking valves

DWorn camshaft lobe(s)

DCamshaft drive belt slipped or stripped

DIncorrect valve timing

DBroken valve springs

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 22

22 1. Check for faulty motor mounts. Refer to

Engine

Mechanical

for inspection of mounts.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 23

23 1. Review all diagnostic procedures within this table.

2. If all procedures have been completed and no

malfunctions have been found, review/inspect the

following:

DVisual/physical inspection

DTech 2 data

DFreeze Frame data/Failure Records butter

DAll electrical connections within a suspected

circuit and/or system

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair

Contact

Technical

Assistance

Hesitation, Sag, Stumble Symptom

Step Action Value(s) YesNo

1DEFINITION:

Momentary lack of response as the accelerator is

pushed down. Can occur at any vehicle speed. Usually

most pronounced when first trying to make the vehicle

move, as from a stop sign. May cause the engine to stall

if severe enough.

Was the “On-Board Diagnostic (OBD) System Check”

performed? —Go to

Step 2

Go to

OBD

System

Check

21. Perform a bulletin search.

2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom? — Verify repair Go to

Step 3

3Was a visual/physical check performed?

—Go to

Step 4

Go to

Visual/Physic

al Check

41. Check the fuel control heated oxygen sensors

(HO2S). The fuel control heated oxygen sensors

(HO2S) should respond quickly to different throttle

positions. If they don’t, check them for silicon or

other contaminants from fuel or use of improper

RTV sealant. The sensors may have a white

powdery coating.

Silicon contamination causes a high but false

HO2S signal voltage (rich exhaust indication).

The ECM will then reduce the amount of fuel

delivered to the engine, causing a severe

driveability problem. For more information, refer

Engine Control Module (ECM) and Sensors

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 5

51. Check the fuel pressure. Refer to

Fuel System

Pressure Test

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 6

6Observe the TP angle display on the Tech 2 while

slowly increasing throttle pedal.

Does the TP angle display steadily increase from 0% at

closed throttle to 100% at WOT? —Go to

Step 7

Go to

Step 18

7Monitor the long term fuel trim on the Tech 2.

Is the long term fuel trim significantly in the negative

range (rich condition)? —Go to

Step 8

Go to

Step 9

81. Check items that can cause the engine to run rich.

Refer to

Diagnostic Aids

DTC P0172 Diagnostic

Support

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 10

91. Check items that can cause the engine to run lean.

Refer to

Diagnostic Aids

DTC P0171 Diagnostic

Support

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 10

Step NoYesValue(s)Action

10 1. Check for proper ignition voltage output with spark

tester J 26792 (ST-125). Refer to

Electronic Ignition

System

for the procedure.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 11

11 1. Check for a loose ignition coil ground.

Refer to

Electronic Ignition System

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 12

12 1. Check the ignition coils for cracks or carbon

tracking.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 13

13 1. Remove spark plugs and check for wet plugs,

cracks, wear, improper gap, burned electrodes, or

heavy deposits. Refer to

Electronic Ignition

System

NOTE: If spark plugs are gas or oil fouled, the cause of

the fouling must be determined before replacing the

spark plugs.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 14

14 1. Check the ECM grounds for clearness, tightness

and proper routing. Refer to the ECM wiring

diagrams in Electrical Diagnosis.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 15

15 1. Check the MAF sensor connections.

2. If a problem is found, replace the faulty terminals as

necessary. Refer to

Electrical Diagnosis

for wiring

repair procedures.

Was a problem found? — Verify repair Go to

Step 16

16 1. Visually/physically check vacuum hoses for splits,

kinks, and proper connections and routing as

shown on the “Vehicle Emission Control

Information” label.

2. If a problem is found, repair as necessary.

Was a problem found? — Verify repair Go to

Step 17

Step NoYesValue(s)Action

17 1. Review all diagnostic procedures within this table.

2. If all procedures have been completed and no

malfunctions have been found, review/inspect the

following:

DVisual/physical inspection

DTech 2 data

DFreeze Frame data/Failure Records butter

DAll electrical connections within a suspected

circuit and/or system

3. If a problem is found, repair as necessary.

Was a problem found? — Verify repair

Contact

Technical

Assistance

18 Replace the TP sensor.

Is the action complete? — Verify repair —

Default Matrix Table

Service Procedure Default Strategy

A referral strategy has been established to assist the

technician with additional information when the cause of

the failure cannot be determined. If no problem is found

after performing diagnostics, then refer to the default

matrix table for further diagnostic information.

Default Matrix Table

Strategy Based Diagnostic Charts Initial Diagnosis Default Section(s)

On-Board Diagnostic (OBD) System

Check Vehicle does not enter diagnostics. Chassis Electrical

On-Board Diagnostic (OBD) System

Check Vehicle enters diagnostics and

communicates with the Tech 2. MIL is

“ON” in diagnostics. Engine does not

start and run.

Ignition System Check

On-Board Diagnostic (OBD) System

Check Engine starts and runs, no ECM codes

set. Customer complains of vibration. —

On-Board Diagnostic (OBD) System

Check Engine starts and runs, no ECM codes

set. Customer complains of harsh or

soft shift, poor performance, delayed or

no engagement into drive or reverse,

transmission fluid leak, transmission

noise or vibration, or improper TCC

operation.

Automatic Transmission

ECM Power and Ground Check On-Board Diagnostic (OBD) System

Check. Chassis Electrical

ECM Power and Ground Check On-Board Diagnostic (OBD) System

Check. ECM power and ground circuits

OK. Data link voltage incorrect.

Chassis Electrical

On-Board Diagnostic (OBD) System

Check Engine starts and runs, no ECM codes

set. Customer complains of harsh or

soft shift, poor performance, delayed or

no engagement into drive or reverse,

transmission fluid leak, transmission

noise or vibration, or improper TCC

operation.

Automatic Transmission

Symptoms Initial Diagnosis Default Section(s)

Intermittents 1. On-board diagnostic (OBD)

system check.

2. Careful visual/physical inspections.

Chassis Electrical

Hard Starts 1. OBD system check.

2. Sensors (ECT, BARO, MAF, TP) ;

BARO output chart.

3. Fuel system electrical test, fuel

system diagnosis.

4. Ignition system.

5. IAC system check.

Engine Mechanical, Ignition

System Check, Exhaust System

Diagnosis

Surges and/or Chuggles 1. OBD system check.

2. Heated oxygen sensors.

3. Fuel system diagnosis.

4. Ignition system.

Calibration ID “Broadcast”

/Service Bulletins, Ignition

System Check, Generator

Output, Exhaust System

Diagnosis

Lack of Power, Sluggish or Spongy 1. OBD system check.

2. Fuel system diagnosis.

3. Ignition system.

Refer to

Exhaust System

Engine Exhaust

, TCC

Operation, Calibration

ID/Service Bulletins

Detonation/Spark Knock 1. OBD system check.

2. Transmission range switch.

3. TCC operation.

4. Fuel system diagnosis.

5. Ignition system.

TCC operation, Cooling System,

Ignition System Check,

Calibration ID/Service Bulletins

Hesitation, Sag, Stumble 1. OBD system check.

2. TP.

3. BARO output check.

4. Fuel system diagnosis.

5. EVAP emission canister purge

valve.

6. Ignition system.

Generator Output Voltage (refer

Chassis Electrical

Calibration ID/Service Bulletins,

Ignition System Check

Cuts Out, Misses 1. OBD system check.

2. Cylinder balance test. Ignition System Check

Rough, Unstable, or Incorrect Idle,

Stalling 1. OBD system check.

2. Fuel injector and fuel injector

balance test.

3. EVAP emission canister purge

valve check.

4. Ignition system.

5. IAC operation.

BARO Output Check, Throttle

Linkage, IAC System Check,

A/C Clutch Control Circuit

Diagnosis, Crankcase

Ventilation System, Calibration

ID/Service Bulletins, Generator

Output Voltage (refer to

Chassis

Electrical

), Exhaust Diagnosis

Poor Fuel Economy 1. OBD system check.

2. Careful visual/physical inspection.

3. Ignition system.

4. Cooling system.

TCC Operation, Exhaust

System (refer to

Engine

Exhaust

)

Engine Cranks But Will Not Run 1. OBD system check. Fuel System Electrical

Diagnosis, Fuel System

Diagnosis, Fuel Injector and

Fuel Injector Balance Test.

Excessive Exhaust Emissions or

Odors 1. OBD system check.

2. Emission test.

3. Cooling system.

4. Fuel system diagnosis.

5. Fuel injector and fuel injector

balance test.

6. EVAP emission canister purge

valve.

7. Crankcase ventilation system.

8. Ignition system.

9. BARO output check.

Exhaust Diagnosis, Calibration

ID/Service Bulletins

Dieseling, Run-On 1. OBD system check.

2. Careful visual/physical inspection.

3. Fuel system diagnosis.

—

Backfire 1. OBD system check.

2. Ignition system.

3. Fuel system diagnosis.

4. Fuel injector and fuel injector

balance test.

Exhaust System Diagnosis,

Intake Casting Flash, Ignition

System Check

Catalyst Monitor 1. OBD system check.

2. Careful visual/physical inspection.

3. Heated oxygen sensors.

Exhaust System

Fuel Trim 1. OBD system check.

2. Careful visual/physical inspection.

3. Fuel system diagnosis.

4. Heated oxygen sensors, MAF

sensors.

Exhaust System Intake Air

System

Evaporative Emissions 1. OBD system check.

2. Careful visual/physical inspection.

3. Fuel system diagnosis.

—

Heated Oxygen Sensors 1. OBD system check.

2. Careful visual/physical inspection. Exhaust System

Camshaft Position (CMP)

Sensor

Removal Procedure

1.Disconnect the negative battery cable.

2.Remove the engine cover.

3.Remove the common chamber assembly.

Refer to Common Chamber in Engine Mechanical.

014RW120

4.Disconnect the electrical connector to the CMP

sensor.

014RV053

5.Remove the CMP retaining bolt from the side of left

cylinder head.

6.Remove the CMP sensor from the cylinder head.

Inspection Procedure

1.Inspect the sensor O-ring for cracks or leaks.

2.Replace the O-ring if it is worn or damaged.

3.Lubricate the new O-ring with engine oil.

4.Install the lubricated O-ring.

Installation Procedure

1.Install the CMP sensor in the cylinder head.

2.Install the CMP sensor retaining bolt.

Tighten

DTighten the retaining screw to 9 N·m

(0.9kg·m/78lbin.).

3.Connect the electrical connector to the CMP sensor.

014RV053

4.Install the common chamber assembly.

Refer to Common Chamber in Engine Mechanical.

060RW044

5.Install the engine cover.

6.Connect the negative battery cable.

Crankshaft Position (CKP)

Sensor

Removal Procedure

1.Disconnect the negative battery cable.

2.Disconnect the electrical connector to the CKP

sensor.

3.Remove one bolt and the CKP sensor from the right

side of the engine block, just behind the mount.

NOTE:Use caution to avoid any hot oil that might drip

out.

TS22909

Inspection Procedure

1.Inspect the sensor O-ring for cracks or leaks.

2.Replace the O-ring if it is worn or damaged.

3.Lubricate the new O-ring with engine oil.

4.Install the lubricated O-ring.

Installation Procedure

1.Install the CKP sensor in the engine block.

2.Install the CKP sensor mounting bolt.

Tighten

DTighten the mounting bolt to 9 N·m

(0.9kg·m/78lbin.).

TS22909

3.Connect the electrical connector to the CKP sensor.

4.Connect the negative battery cable.

Engine Coolant Temperature

(ECT) Sensor

Removal Procedure

NOTE:Care must be taken when handling the engine

coolant temperature (ECT) sensor. Damage to the ECT

sensor will affect proper operation of the fuel injection

system.

1.Disconnect the negative battery cable.

2.Drain the radiator coolant. Refer to

Draining and

Refilling Cooling System

Engine Cooling

3.Disconnect the electrical connector.

014RW127

4.Remove the ECT sensor from the coolant crossover.

014RW086

Installation Procedure

1.Apply sealer or the equivalent to the threads of the

ECT sensor.

2.Install the ECT sensor in the coolant crossover.

Tighten

DTighten the ECT sensor to 30 N·m

(3.1kg·m/22lbft.).

014RW086

3.Connect the electrical connector.

014RW085

4.Fill the radiator with coolant. Refer to

Draining and

Refilling Cooling System

Engine Cooling

5.Connect the negative battery cable.

Heated Oxygen Sensor (HO2S)

Removal Procedure

1.Disconnect the negative battery cable.

2.Locate the four oxygen sensors.

060RW035

DSensor is mounted before the left-hand catalytic

converter.

3.Disconnect the pigtail from the wiring harness.

IMPORTANT:The pigtail is permanently attached to

the sensor. Be careful not to pull the wires out.

NOTE: Do not use a torch to remove an HO2S unless the

sensor is being replaced. Using a torch could damage the

sensor.

4.Remove the sensor from the exhaust pipe.

DBecause of the expansion and contraction of the

metal in the exhaust system over time, this may be

difficult if the engine temperature is below 48°C

(120°F).

060RW114

Inspection Procedure

All four sensors are identical. Inspect each in the same

way.

1.Inspect the pigtail and the electrical connector for

grease, dirt, corrosion, and bare wires or worn

insulation.

2.Inspect the louvered end of the sensor for grease,

dirt, or other contaminations.

060RW114

Installation Procedure

IMPORTANT:

DA special anti-seize compound, P/N 5613695, is used

on the HO2S threads. This compound consists of

glass beads suspended in a liquid graphite solution.

The graphite burns away with engine heat, but the

glass beads will remain, making the sensor easier to

remove.

DNew or service sensors will already have the

compound applied to the threads. If a sensor is

removed and is to be reinstalled for any reason, the

threads must have anti-seize compound applied.

1.Apply anti-seize compound or the equivalent to the

threads of the oxygen sensor, if necessary.

2.Install the oxygen sensor on the exhaust pipe in its

original position.

Tighten

DTighten the oxygen sensor to 55 N·m

(5.5 kg·m/40 lb in.).

060RW114

3.Connect the pigtail to the wiring harness.

4.Connect the negative battery cable.

Intake Air Temperature (IAT)

Sensor

Removal Procedure

1.Disconnect the negative battery cable.

2.Remove the engine cover

3.The IAT sensor is located in the intake air duct, behind

the throttle body.

4.Disconnect the electrical connector from the IAT

sensor.

TS23741

5.Remove the IAT sensor from the intake air duct by

using a rocking motion while pulling the sensor.

Installation Procedure

1.Install the IAT sensor into the grommet in the intake

air duct.

2.Correct the IAT electrical connector.

TS23741

3.Install the engine cover.

4.Connect the negative battery cable.

Mass Air Flow (MAF) Sensor

Removal Procedure

1.Disconnect the negative battery cable.

2.Disconnect the electrical connector from the MAF

sensor.

3.Loosen the MAF sensor bolt (2) and remove the MAF

sensor (1).

060RW071

Installation Procedure

1.Install the MAF sensor on the air duct.

2.Install bolt (2) the MAF sensor.

060RW071

3.Connect the negative battery cable.

Barometric Pressure (BARO)

Sensor

Removal Procedure

1.Disconnect the negative battery cable.

2.Disconnect the electrical connector from the BARO

sensor.

060RW024

3.Remove the BARO sensor from the mounting

bracket.

Installation Procedure

1.Install the BARO sensor in the mounting bracket.

2.Connect the BARO electrical connector.

060RW024

3.Connect the negative battery cable.

Malfunction Indicator Lamp

(MIL)

Removal and Installation Procedure

Refer to Warning light bulb, indicator light valve,

illumination light bulb, A/T indicator light bulb in Meter and

Gauge.

Engine Control Module (ECM)

Service Precaution

NOTE: To prevent possible electrostatic discharge

damage to the ECM, do not touch the connector pins or

soldered components on the circuit board.

Electrostatic Discharge (ESD)

Damage

Electronic components used in the control systems are

often designed to carry very low voltage. Electronic

components are susceptible to damage caused by

electrostatic discharge. Less than 100 volts of static

electricity can cause damage to some electronic

components. By comparison, it takes as much as 4,000

volts for a person to even feel the zap of a static

discharge.

There are several ways for a person to become statically

charged. The most common methods of charging are by

friction and by induction. An example of charging by

friction is a person sliding across a car seat.

Charging by induction occurs when a person with well

insulated shoes stands near a highly charged object and

momentarily touches ground. Charges of the same

polarity are drained off leaving the person highly charged

with the opposite polarity. Static charges can cause

damage, therefore, it is important to use care when

handling and testing electronic components.

NOTE:To prevent possible Electrostatic Discharge

damage, follow these guidelines:

DDo not touch the control module connector pins or

soldered components on the control module circuit

board.

DDo not open the replacement part package until the

part is ready to be installed.

DBefore removing the part from the package, ground

the package to a known good ground on the vehicle.

DIf the part has been handled while sliding across the

seat, or while sitting down from a standing position, or

while walking a distance, touch a known good ground

before installing the part.

NOTE:To prevent internal ECM damage, the ignition

must be in the “OFF” position in order to disconnect or

reconnect power to the ECM (for example: battery cable,

ECM pigtail, ECM fuse, jumper cables, etc.).

IMPORTANT:When replacing the production ECM

with a service ECM, it is important to transfer the

broadcast code and production ECM number to the

service ECM label. This will allow positive identification of

ECM parts throughout the service life of the vehicle. Do

not record this information on the metal ECM cover.

IMPORTANT:The ignition should always be in the

“OFF” position in order to install or remove the ECM

connectors.

Service of the ECM should normally consist of either re-

placement of the ECM. If the diagnostic procedures call

for the ECM to be replaced, the ECM should be checked

first to ensure it is the correct part. If it is, remove the

faulty ECM and install the new service ECM.

DTC P0601 indicates the check sum error.

Removal Procedure

1.Disconnect the negative battery cable.

2.Disconnect the ECM connector.

3.Remove the four bolts.

4.Remove the ECM from the common chamber.

Installation Procedure

1.Install the ECM with four bolts on the common

chamber.

2.Connect the ECM connector.

060RW025

3.Connect the negative battery cable.

If the ECM is replaced, the new ECM will need to be

programmed. EEPROM

General Description

The Electronically Erasable Programmable Read Only

Memory (EEPROM) is a permanent memory that is

physically soldered within the ECM. The EEPROM

contains program and calibration information that the

ECM needs to control powertrain operation.

Functional Check

1.Perform the On-Board Diagnostic System Check.

2.Start the engine and run for one minute.

3.Scan for DTCs using the Tech 2.

Power Steering Pressure (PSP)

Switch

General Description

The Power Steering Pressure (PSP) switch closes when

the hydraulic pressure reaches 3920 ± 690 kpa (570 ± 100

psi). This causes the ECM to actuate the idle air control

valve in order to prevent the additional load from slowing

down the engine. The switch opens when the hydraulic

pressure drops to 2970 ± 560 kpa (430 ± 80 psi).

Removal Procedure

1.Disconnect the PSP switch pigtail from the wiring

harness.

DThe pigtail is permanently attached to the switch.

Do not attempt to remove the wires from the

sensor.

DHave a container ready to catch the power steering

fluid that leaks out of the line when the switch is

removed.

2.Remove the PSP switch from the power steering line.

DPlug the line to prevent excessive loss of fluid and

possible contamination of the power steering

system.

TS23760

Installation Procedure

1.Install the PSP switch in the power steering line.

TS23760

2.Connect the PSP switch pigtail to the wiring harness.

3.Check the power steering fluid level. Refer to

Power

Steering

4.Start the engine. Watch the PSP switch for signs of

fluid leakage.

Throttle Position (TP) Sensor

Removal Procedure

1.Disconnect the negative battery cable.

2.Disconnect the TPS electrical connector.

3.Remove the bolts and the TP sensor from the throttle

body.

060RW112

NOTE:Do not clean the TP sensor by soaking it in

solvent. The sensor will be damaged as a result.

Function Check

Use a Tech 2 to check the TP sensor output voltage at

closed throttle.

DThe voltage should be under 0.85 volt.

DIf the reading is greater than 0.85 volt, check the

throttle shaft to see if it is binding. Check that the

throttle cable is properly adjusted, also. Refer to

Throttle Cable Adjustment

DIf the throttle shaft is not binding and the throttle cable

is properly adjusted, install a new TP sensor.

Installation Procedure

1.Install the TP sensor on the throttle body with the

bolts.

060RW112

2.Connect the TP electrical connector.

3.Install the negative battery cable.

Vehicle Speed Sensor (VSS)

Removal Procedure

CAUTION:The VSS is located on the right side of

the transfer case just ahead of the rear propeller

shaft and very close to the exhaust pipes. Be sure

that the exhaust pipes are cool enough to touch

before trying to remove the VSS. If the pipes are hot,

you could be burned.

1.Disconnect the negative battery cable.

2.Disconnect the VSS electrical connector.

TS23748

3.Remove the bolt and the clamp securing the VSS in

place.

IMPORTANT:Have a container ready to catch any fluid

that leaks out when the VSS is removed from the transfer

case.

TS23780

4.Remove the VSS from the transfer case by wiggling it

slightly and pulling it straight out.

Inspection Procedure

1.Inspect the electrical connector for signs of corrosion

or warping. Replace the VSS if the electrical

connector is corroded or warped.

2.Inspect the VSS driven gear for chips, breaks, or worn

condition. Replace the VSS if the driven gear is

chipped, broken or worn.

3.Inspect the O-ring for wear, nicks, tears, or

looseness. Replace the O-ring if necessary.

Installation Procedure

1.Install the VSS in the transfer case with the notch for

the connector facing the rear.

2.Secure the VSS in place with the clamp and the bolt.

Tighten

DTighten the bolt to 16 N·m (1.6 kg·m/12 lb ft.).

TS23780

3.Connect the VSS electrical connector.

TS23748

4.Check the transfer case oil level. Add fluid if

necessary.

5.Connect the negative battery cable.

Air Cleaner/Air Filter

Removal Procedure

1.Loosen the clamp between the air cleaner lid and the

duct.

2.Release the four latches securing the lid to the air

cleaner housing.

3.Remove the air cleaner lid.

4.Remove the air filter element.

060RW070

5.Remove the retaining bolts and the air cleaner

housing from the vehicle.

Installation Procedure

1.Install the air cleaner housing in the vehicle with the

retaining bolts.

2.Install the air filter element in the air cleaner housing.

060RW070

3.Install the air cleaner lid on the air duct and the air

cleaner housing.

4.Tighten the clamp and secure the four latches

between the lid and the air cleaner housing.

Idle Air Control (IAC) Valve

Removal Procedure

1.Disconnect the negative battery cable.

2.Disconnect the IAC electrical connector.

3.Remove the bolts and the IAC valve from the throttle

body.

NOTE:Do not clean the IAC valve by soaking it in

solvent. The valve will be damaged as a result.

060RW063

Cleaning, Inspection, and

Measurement Procedure

DClean the IAC valve O-ring sealing surface, pintle

valve seat and air passage.

–Use carburetor cleaner and a parts cleaning

brush to remove carbon deposits. Do not use a

cleaner that contains methyl ethyl ketone. This

is an extremely strong solvent and not

necessary for this type of deposit.

–Shiny spots on the pintle are normal and do not

indicate misalignment or a bent pintle shaft.

–If the air passage has heavy deposits, remove

the throttle body for complete cleaning.

060RW115

DInspect the IAC valve O-ring for cuts, cracks, or

distortion. Replace the O-ring if damaged.

DIn order to install a new IAC valve, measure the

distance between the tip of the pintle and the

mounting flange. If that measurement is 28 mm (1.1

in.) or less, the valve needs no adjustment. If the

measurement is greater than 28 mm (1.1 in.), apply

finger pressure and retract the valve. The force

required to retract the pintle on a new valve will not

damage the valve, shaft, or pintle.

NOTE:Do not push or pull on the IAC valve pintle on IAC

valves that have been in service. The force required to

move the pintle may damage it.

IMPORTANT:Use an identical replacement part in

order to replace a valve. IAC valve pintle shape and

diameter are designed for the specific application.

060RW115

Installation Procedure

1.Install the IAC valve on the throttle body with the bolts.

Tighten

DTighten the bolts to 1 N·m (0.1kg·m/9lbin.).

060RW063

2.Connect the IAC valve electrical connector.

3.Install the negative battery cable.

Common Chamber

Removal and Installation Prodedure

Refer to Common Chamber in Engine Mechanical.

Accelerator Cable Assembly

Removal Procedure

1.Loosen the nut on the cable bracket mounting on the

common chamber.

101RW005

2.Remove the accelerator control cable (on the throttle

valve end).

101RW006

3.Remove the accelerator control cable (on the

accelerator pedal end).

TS23982

4.Remove the grommet.

5.Remove the accelerator control cable.

TS23983

Inspection Procedure

Check the following items, and replace the control cable if

any abnormality is found:

DThe control cable should move smoothly.

DThe control cable should not be bent or kinked.

DThe control cable should be free of damage and

corrosion.

Installation Procedure

1.Install the accelerator control cable.

TS23983

2.Install the grommet.

3.Install the accelerator control cable (on the

accelerator pedal end).

TS23982

4.Install the accelerator control cable (on the throttle

valve end).

101RW006

5.Install the nut.

101RW007

Accelerator Pedal Replacement

Removal Procedure

1.Disconnect the cruise control cable from the

accelerator pedal assembly.

TS24053

2.Disconnect the accelerator pedal control cable from

the accelerator pedal assembly.

TS24054

3. Disconnect the wiring harness from the kick-down

switch.

TS24038

4.Remove the two screws from the accelerator pedal

assembly.

TS24055

5.Remove the accelerator pedal assembly from the

bulkhead.

Installation Procedure

1.Install the accelerator pedal assembly on the

bulkhead.

2.Install the two screws to the accelerator pedal

assembly.

TS24055

3.Connect the wiring harness to the kick-down switch.

TS24038

4. Connect the accelerator pedal control cable to the

accelerator pedal assembly.

TS24054

5.Connect the cruise control cable to the accelerator

pedal assembly.

TS24053

Fuel Fillter Cap

General Description

The fuel filler cap includes a vacuum valve and a pressure

valve.

If high vacuum or high pressure occurs in the fuel tank,

each valve works to adjust the pressure in order to

prevent damage to the tank at the EGR valve.

TS23767

Inspection Procedure

NOTE: Replace the fuel filler cap with the same type of

filler cap that was originally installed on the vehicle.

DCheck the seal ring in the filler cap for any abnormality

and for seal condition.

DReplace the filler cap if any abnormality is found.

Fuel Filter

Removal Procedure

1.Disconnect the negative battery cable.

2.Remove the fuel filler cap.

3.Disconnect the fuel line from the fuel filter on the

engine side.

4.Disconnect the fuel line from the fuel filter on the fuel

tank side.

041RW006

5.Remove the bolt on the fuel filter holder.

041RW007

6.Remove the fuel filter.

041RW008

Inspection Procedure

1.Replace the fuel filter when the following occur:

DFuel leaks from the fuel filter body.

DThe fuel filter body is damaged.

DThe fuel filter is clogged with dirt or sediment.

2.If the drain hole is clogged, clean the drain.

Installation Procedure

1.Install the fuel filter in the correct direction.

041RW008

2.Install the bolt on the fuel filter holder.

041RW007

3.Connect the fuel line on the engine side.

4.Connect the fuel line on the fuel tank side.

041RW006

5.Install the fuel filler cap.

6.Connect the negative battery cable.

Fuel Gauge Unit

Removal Procedure

Refer to

Fuel Gauge Unit In Engine Fuel.

060RW068

Fuel Injectors

Removal Procedure

NOTE:If the fuel injectors are leaking, the engine oil may

be contaminated with fuel. Check the oil for signs of

contamination and change the oil and the filter if

necessary.

NOTE:Use care in removing the fuel injectors in order to

prevent damage to the fuel injector electrical connector

pins or the fuel injector nozzles. The fuel injector is an

electrical component and should not be immersed in any

type of cleaner as this may damage the fuel injector.

IMPORTANT:Fuel injectors are serviced as a complete

assembly only.

1.Disconnect the negative battery cable.

2.Remove the upper intake manifold. Refer to

Common Chamber in Engine Mechanical.

3.Remove the fuel rail. Refer to

Fuel Rail

060RW044

4.Remove the injector retainer clip.

F06RW017

5.Remove the fuel injector assembly.

6.Remove the O-ring from the fuel injector.

7.Remove the O-ring backup from the fuel injector .

Inspection Procedure

1.Inspect the O-rings for cracks or leaks.

2.Replace worn or damaged O-rings.

3.Lubricate the new O-rings with engine oil before

installation.

Installation Procedure

1.Install the O-ring backup on the fuel injector.

2.Install the new O-ring on the fuel injector.

3.Install the fuel injector on the fuel rail.

F06RW017

4.Use new fuel injector retainer clips to retain the fuel

injector to the fuel rail.

5.Coat the end of the fuel injector with engine oil.

6.Install the fuel rail. Refer to

Fuel Rail

060RW044

7.Install the upper intake manifold. Refer to

Common

Chamber in Engine Mechanical.

8.Install the engine cover.

9.Connect the negative battery cable.

Fuel Pressure Regulator

Removal Procedure

CAUTION:To reduce the risk of fire and personal

injury, it is necessary to relieve the fuel system

pressure before servicing the fuel system

components.

CAUTION:After relieving the system pressure, a

small amount of fuel may be released when servicing

fuel lines or connections. Reduce the chance of

personal injury by covering the fuel line fittings with

a shop towel before disconnecting the fittings. The

towels will absorb any fuel that may leak out. When

the disconnect is completed, place the towel in an

approved container.

NOTE:Compressed air must never be used to test or

clean a fuel pressure regulator, as damage to the fuel

pressure regulator may result.

NOTE:To prevent damage to the fuel pressure regulator,

do not immerse the pressure regulator in solvent.

1.Depressurize the fuel system. Refer to

Fuel Pressure

Relief Procedure

2.Disconnect the negative battery cable.

3.Remove the fuel pump relay. Refer to

Fuel Pump

Relay

4.Remove the pressure regulator hose from the fuel

pressure regulator.

5.Remove the two bolts from the protector that secures

the common chamber.

060RW066

6.Remove the fuel pressure regulator attaching screw.

060RW116

7.Remove the fuel pressure regulator from the fuel rail.

Disassembly Procedure

1.Remove the O-ring from the fuel pressure regulator.

2.Loosen the swivel nut.

3. Remove the fuel return line from the fuel pressure

regulator.

4.Remove the O-ring from the fuel return line.

DThe O-ring may be left inside the fuel pressure

regulator instead of on the fuel return line.

060RW116

Assembly Procedure

1.Install a new O-ring on the fuel return line.

2.Install the fuel return line on the fuel pressure

regulator.

NOTE: Do not over-tighten the swivel nut on the fuel

pressure regulator. The fuel pressure regulator can be

damaged and fuel may leak if the swivel nut is

over-tightened.

3.Tighten the swivel nut.

4.Install a new O-ring on the fuel pressure regulator.

Installation Procedure

1.Install the fuel pressure regulator attaching screw.

Tighten

DTighten the fuel pressure regulator attaching

screw to 3 N·m (0.3 kg·m/26 lb in.).

060RW116

2.Install the fuel pressure regulator on the fuel rail.

3.Install the two bolts to the protector that secures the

common chamber.

060RW066

4.Install the pressure regulator hose to the fuel

pressure regulator.

5.Install the fuel pump relay. Refer to

Fuel Pump Relay

6.Connect the negative battery cable.

7.Crank the engine until it starts. Cranking the engine

may take longer than usual due to trapped air in the

fuel lines.

Fuel Metering System

Fuel Pressure Relief Procedure

CAUTION:To reduce the risk of fire and personal

injury, it is necessary to relieve the fuel system

pressure before servicing the fuel system

components.

CAUTION:After relieving the system pressure, a

small amount of fuel may be released when servicing

fuel lines or connections. Reduce the chance of

personal injury by covering the fuel line fittings with

a shop towel before you disconnect the fittings. The

towels will absorb any fuel that may leak out. When

the disconnect is completed, place the towel in an

approved container.

1.Remove the fuel cap.

2.Remove the fuel pump relay from the underhood

relay box. Refer to

Fuel Pump Relay

060RW067

3.Start the engine and allow it to stall.

4.Crank the engine for 30 seconds.

5.Disconnect the negative battery cable.

Fuel Pump Assembly

Removal Procedure

Refer to

Fuel Tank In Fuel Pump Relay.

060RW068

Fuel Pump Relay

Removal Procedure

1.Remove the fuse and relay box cover from under the

hood.

2.Consult the diagram on the cover to determine which

is the correct relay.

3.Pull the relay straight up and out of the fuse and relay

box.

060RW067

Installation Procedure

1.Insert the relay into the correct place in the fuse and

relay box with the catch slot facing forward.

060RW067

2.Press down until the catch engages.

DAn audible “click” will be heard.

3.Install the fuse and relay box cover.

Fuel Rail Assembly

Removal Procedure

NOTE:

DDo not attempt to remove the fuel inlet fitting on the

fuel rail. It is staked in place. Removing the fuel inlet

fitting will result in damage to the fuel rail or the

internal O-ring seal.

DUse care when removing the fuel rail assembly in

order to prevent damage to the injector electrical

connector terminals and the injector spray tips.

DFittings should be capped and holes plugged during

servicing to prevent dirt and other contaminants from

entering open lines and passages.

IMPORTANT:Before removal, the fuel rail assembly

may be cleaned with a spray type engine cleaner. Follow

the spray package instructions. Do not immerse the fuel

rails in liquid cleaning solvent.

1.Depressurize the fuel system. Refer to Fuel Pressure

Relief Procedure in this Section.

2.Disconnect the negative battery cable.

3.Remove the engine cover.

4.Disconnect the accelerator pedal cable from throttle

body and cable bracket.

5.Disconnect the connectors from, solenoid valve,

sensing valve.

6.Disconnect the vacuum hose on canister VSV and

positive crankcase ventilation hose.

7.Remove the common chamber Refer to the common

chamber in Engine Mechanical.

1)Lift up carefully on the fuel injectors. Do not

separate the fuel injectors from the fuel rail.

2)If an injector becomes separated from the fuel rail,

the infector O-ring seals and the retainer clip must

be replaced.

3)Drain residual fuel into an approved container.

060RW044

8.If removal of the fuel pressure regulator is necessary,

refer to

Fuel Pressure Regulator

9.If removal of the fuel injectors is necessary, refer to

Fuel Injectors

Installation Procedure

1.If the fuel injectors were removed, install them. Refer

Fuel Injectors

2.If the fuel pressure regulator was removed, install it.

Refer to

Fuel Pressure Regulator

3.Install the common chamber. Refer to common

chamber in engine Mechanical.

060RW044

4.Connect the vacuum hose on Canister VSV and

positive crankcase ventilation hose.

5.Connect the connectors to, solenoid valve.

6.Connect the accelerator pedal cable to throttle body

and cable bracket.

7.Install the engine cover.

8.Connect the negative battery cable.

9.Crank the engine until it starts. Cranking the engine

may take longer than usual due to trapped air in the

fuel rail and in the injectors.

Fuel Tank

Removal Procedure

Refer to

Fuel Tank In Fuel Pump Relay.

060RW068

Throttle Body (TB)

Removal Procedure

1.Disconnect the negative battery cable.

2.Drain the cooling system. Refer to

Cooling System

3.Remove the accelerator cable assembly. Refer to

Accelerator Cable in Engine Speed Control System.

4.Disconnect the electrical connectors:

DThrottle position (TP) sensor.

DIdle air control (IAC) solenoid.

DIntake air temperature (IAT) sensor. Refer to

Intake

Air Temperature Sensor

5.Disconnect the vacuum hose below the air horn.

6.Remove the intake air duct clamp.

7.Disconnect the intake air duct.

8.Disconnect the coolant lines from the throttle body.

9.Remove the bolts from the common chamber.

10.Remove the throttle body from the common chamber.

11.Remove the gasket from the upper intake manifold.

060RW065

12.Remove the IAC. Refer to

Idle Air Control (IAC)

Solenoid

13.Remove the TP sensor. Refer to

Throttle Position

(TP) Sensor

Inspection Procedure

NOTE:Do not use solvent of any type when you clean the

gasket surfaces on the intake manifold and the throttle

body assembly. The gasket surfaces and the throttle

body assembly may be damaged as a result.

DIf the throttle body gasket needs to be replaced,

remove any gasket material that may be stuck to the

mating surfaces of the manifold.

DDo not leave any scratches in the aluminum casting.

Installation Procedure

1.Install the TP sensor. Refer to

Throttle Position (TP)

Sensor

2.Install the IAC. Refer to

Idle Air Control (IAC)

Solenoid

3.Install the gasket on the common chamber.

4.Install the throttle body on the common chamber.

5.Secure the gasket and the throttle body with the four

bolts.

DThe vacuum lines must be properly routed under

the throttle body before tightening the mounting

bolts.

Tighten

DTighten the throttle body mounting bolts to 24

N·m (2.4kg·m/17lbft.).

060RW065

6.Install the coolant lines.

7.Connect all the vacuum lines.

8.Install the intake air duct.

9.Tighten the intake air duct clamp.

10.Connect all the electrical connectors:

DThrottle position (TP) sensor.

DIdle air control (IAC) solenoid.

DIntake air temperature (IAT) sensor. Refer to

Intake

Air Temperature Sensor

11.Install the accelerator cable assembly. Refer to

Accelerator Cable in Engine Speed Control System.

12.Fill the cooling system. Refer to

Cooling System

13.Install the negative battery cable.

Electronic Ignition System

Removal Procedure

1.Disconnect the negative battery cable.

2.Disconnect the electrical connector at the coil

module.

3.Remove the two screws that secure the coil module to

the rocker cover.

014RW108

4.Remove the coil module and the spark plug boot from

the spark plug.

DTwist the coil module while pulling it straight up.

060RW117

5. Use the spark plug socket in order to remove the

spark plug from the engine.

Spark Plug Gap Check

DCheck the gap of all spark plugs before installation.

DUse a round wire feeler gauge to ensure an accurate

check.

DPlugs installed with the wrong gap can cause poor

engine performance and excessive emissions.

Installation Procedure

NOTE:The plug must thread smoothly into the cylinder

head and be fully seated. Use a thread chaser if

necessary to clean the threads in the cylinder head.

Cross-threading or failure to fully seat the spark plug can

cause plug overheating, exhaust blow-by gases, or

thread damage. Do not overtighten the spark plugs. Over

tightening can cause aluminum threads to strip.

1.Install the spark plug in the engine. Use the

appropriate spark plug socket.

Tighten

DTighten the spark plug to 18 N·m

(1.8kg·m/13lbft.).

2.Install the coil module and spark plug boot over the

spark plug.

3.Secure the coil module to the rocker cover with two

screws.

060RW117

4.Connect the electrical connector at the coil module.

5.Connect the negative battery cable.

Catalytic Converter

Removal and Installation Procedure

Refer to

Engine Exhaust in Engine

Air Conditioning Relay

Removal Procedure

1.Remove the fuse and relay box cover from under the

hood.

2.Consult the diagram on the cover to determine which

is the correct relay.

3.Pull the relay straight up and out of the fuse and relay

box.

Installation Procedure

1.Insert the relay into the correct place in the fuse and

relay box with the catch slot facing forward.

2.Press down until the catch engages.

DAn audible “click” will be heard.

3.Install the fuse and relay box cover.

EVAP Canister Hoses

Service Information

To view the routing of the EVAP canister hoses, refer to

Vehicle Emission Control Information

Diagnosis

. Use

6148M or equivalent when you replace the EVAP canister

hoses. EVAP Canister

Removal Procedure

1.Disconnect the negative battery cable.

2.Disconnect the hose from the EVAP canister.

060RW073

3.Remove the EVAP canister to the mounting bracket.

Inspection Procedure

1.Inspect the hoses for cracks and leaks.

2.Inspect the canister for a damaged case.

Installation Procedure

1.Slide the canister into mounting bracket the install the

mounting bracket bolt.

2.Install the EVAP canister to the mounting bracket.

060RW073

3.Connect the two hoses to the EVAP canister.

4.Disconnect the negative battery cable.

EVAP Canister Purge Solenoid

Removal Procedure

1.Disconnect the electrical connector from the EVAP

canister purge solenoid.

2.Disconnect the vacuum hoses from the EVAP

canister purge solenoid.

014RW136

3.Remove the EVAP canister purge solenoid retaining

bolt from the upper intake manifold.

4.Remove the EVAP canister purge solenoid.

014RW137

Installation Procedure

1.Install the EV AP canister purge solenoid on the upper

intake manifold.

2.Install the EVAP canister purge solenoid retaining

bolt.

3.Connect the vacuum hoses to the EVAP canister

purge solenoid.

014RW137

4.Connect the electrical connector to the EVAP canister

purge solenoid.

014RW138

Fuel Tank Vent Valve

Removal and Installation Procedure

Refer to

Fuel Pump

Positive Crankcase Ventilation

(PCV) Valve

Removal Procedure

1.Remove the vacuum hose at the PCV valve.

DSlide the clamp back to release the hose.

2.Pull the PCV valve from the rubber grommet in the

right valve cover.

014RW097

Inspection Procedure

1.Shake the valve and listen for the rattle of the needle

inside the valve.

2.If the valve does not rattle, replace the valve.

Installation Procedure

1.Push the PCV valve into the rubber grommet in the

left valve cover.

2.Install the vacuum hose on the PCV valve and secure

the vacuum hose with the clamp.

014RW097

Wiring and Connectors

Wiring Harness Service

The control module harness electrically connects the

control module to the various solenoids, switches and

sensors in the vehicle engine compartment and

passenger compartment.

Replace wire harnesses with the proper part number

replacement.

Because of the low amperage and voltage levels utilized

in powertrain control systems, it is essential that all wiring

in environmentally exposed areas be repaired with crimp

and seal splice sleeves.

The following wire harness repair information is intended

as a general guideline only. Refer to

Chassis Electrical

for

all wire harness repair procedures.

Connectors and Terminals

Use care when probing a connector and when replacing

terminals. It is possible to short between opposite

terminals. Damage to components could result. Always

use jumper wires between connectors for circuit

checking. NEVER probe through Weather-Pack seals.

Use an appropriate connector test adapter kit which

contains an assortment of flexible connectors used to

probe terminals during diagnosis. Use an appropriate

fuse remover and test tool for removing a fuse and to

adapt the fuse holder to a meter for diagnosis.

Open circuits are often difficult to locate by sight because

oxidation or terminal misalignment are hidden by the

connectors. Merely wiggling a connector on a sensor , or

in the wiring harness, may temporarily correct the open

circuit. Intermittent problems may also be caused by

oxidized or loose connections.

Be certain of the type of connector/terminal before

making any connector or terminal repair. Weather-Pack

and Com-Pack III terminals look similar , but are serviced

differently.

Wire Harness Repair: Twisted

Shielded Cable

Removal Procedure

1.Remove the outer jacket.

2.Unwrap the aluminum/mylar tape. Do not remove the

mylar.

047

3.Untwist the conductors.

4.Strip the insulation as necessary.

048

Installation Procedure

1.Splice the wires using splice clips and rosin core

solder.

2.Wrap each splice to insulate.

3.Wrap the splice with mylar and with the drain

(uninsulated) wire.

049

4.Tape over the whole bundle to secure.

050

Twisted Leads

Removal Procedure

1.Locate the damaged wire.

2.Remove the insulation as required.

051

Installation Procedure

1.Use splice clips and rosin core solder in order to splice

the two wires together.

052

2.Cover the splice with tape in order to insulate it from

the other wires.

053

3.Twist the wires as they were before starting this

procedure.

054

4.Tape the wires with electrical tape. Hold in place.

055

Weather-Pack Connector

Tools Required

5-8840-0388-0 Weather-Pack II Terminal Remover

Removal Procedure

A Weather-Pack connector can be identified by a rubber

seal at the rear of the connector. This engine room

connector protects against moisture and dirt, which could

from oxidation and deposits on the terminals. This

protection is important, because of the low voltage and

the low amperage found in the electronic systems.

1.Open the secondary lock hinge on the connector.

070

2.Use tool 5-8840-0388-0 or the equivalent to remove

the pin and the sleeve terminals. Push on

5-8840-0388-0 to release.

NOTE: Do the use an ordinary pick or the terminal may

be bent or deformed. Unlike standard blade terminals,

these terminals cannot be straightened after they have

been improperly bent.

071

3.Cut the wire immediately behind the cable seal.

072

Installation Procedure

Make certain the connectors are properly seated and all

of the sealing rings are in place when you reconnect the

leads. The secondary lock hinge provides a backup

locking feature for the connector. The secondary lock

hinge is used for added reliability. This flap should retain

the terminals even if the small terminal lock tangs are not

positioned properly.

Do not replace the Weather-Pack connections with

standard connections. Read the instructions provided

with the Weather-Pack connector and terminal packages.

1.Replace the terminal.

2.Slip the new seal onto the wire.

3.Strip 5 mm (0.2”) of insulation from the wire.

4.Crimp the terminal over the wire and the seal.

073

5.Push the terminal and the connector to engage the

locking tangs.

070

6.Close the secondary locking hinge.

Com-Pack III

General Information

The Com-Pack III terminal looks similar to some

Weather-Pack terminals. This terminal is not sealed and

is used where resistance to the environment is not

required. Use the standard method when repairing a

terminal. Do not use the Weather-Pack terminal tool

5-8840-0388-0 or equivalent. These will damage the

terminals. Metri-Pack

Tools Required

5-8840-0632-0 Terminal Remover

Removal Procedure

Some connectors use terminals called Metri-Pack Series

150. These may be used at the engine coolant

temperature (ECT) sensor.

1.Slide the seal (1) back on the wire.

2.Insert the 5-8840-0632-0 tool or equivalent (3) in

order to release the terminal locking tang (2).

060

3.Push the wire and the terminal out through the

connector. If you reuse the terminal, reshape the

locking tang.

Installation Procedure

Metri-Pack terminals are also referred to as “pull-to-seat”

terminals.

1.In order to install a terminal on a wire, the wire must be

inserted through the seal (2) and through the

connector (3).

2.The terminal (1) is then crimped onto the wire.

061

3.Then the terminal is pulled back into the connector to

seat it in place.

General Description (ECM and

Sensors)

Reference ECM Input

The engine control module (ECM) uses this signal from

the crankshaft position (CKP) sensor to calculate engine

RPM and crankshaft position at all engine speeds. The

ECM also uses the pulses on this circuit to initiate injector

pulses. If the ECM receives no pulses on this circuit, DTC

P0337 will set. The engine will not start and run without

using the reference signal.

A/C Request Signal

This signal tells the ECM when the A/C mode is selected

at the A/C control head. The ECM uses this to adjust the

idle speed before turning “ON” the A/C clutch. The A/C

compressor will be inoperative if this signal is not

available to the ECM.

Refer to

A/C Clutch Circuit Diagnosis

for A/C wiring

diagrams and diagnosis for the A/C electrical system.

Crankshaft Position (CKP) Sensor

The crankshaft position (CKP) sensor provides a signal

used by the engine control module (ECM) to calculate the

ignition sequence. The CKP sensor initiates the 58X

reference pulses which the ECM uses to calculate RPM

and crankshaft position.

Refer to

Electronic Ignition System

for additional

information.

0013

Camshaft Position (CMP) Sensor and

Signal

The camshaft position (CMP) sensor sends a CMP signal

to the ECM. The ECM uses this signal as a “syncpulse” to

trigger the injectors in the proper sequence. The ECM

uses the CMP signal to indicate the position of the #1

piston during its power stroke. This allows the ECM to

calculate true sequential fuel injection (SFI) mode of

operation. If the ECM detects an incorrect CMP signal

while the engine is running, DTC P0341 will set. If the

CMP signal is lost while the engine is running, the fuel

injection system will shift to a calculated sequential fuel

injection mode based on the last fuel injection pulse, and

the engine will continue to run. As long as the fault is

present, the engine can be restarted. It will run in the

calculated sequential mode with a 1-in-6 chance of the

injector sequence being correct.

Refer to

DTC P0341

for further information.

0014

Engine Coolant Temperature (ECT) Sensor

The engine coolant temperature (ECT) sensor is a

thermistor (a resistor which changes value based on

temperature) mounted in the engine coolant stream. Low

coolant temperature produces a high resistance of

100,000 ohms at –40°C (–40°F). High temperature

causes a low resistance of 70 ohms at 130°C (266°F).

The ECM supplies a 5-volt signal to the ECT sensor

through resistors in the ECM and measures the voltage.

The signal voltage will be high when the engine is cold and

low when the engine is hot. By measuring the voltage, the

ECM calculates the engine coolant temperature. Engine

coolant temperature affects most of the systems that the

ECM controls.

The Tech 2 displays engine coolant temperature in

degrees. After engine start-up, the temperature should

rise steadily to about 85°C (185°F). It then stabilizes

when the thermostat opens. If the engine has not been

run for several hours (overnight), the engine coolant

temperature and intake air temperature displays should

be close to each other . A hard fault in the engine coolant

sensor circuit will set DTC P0118.

0016

Electrically Erasable Programmable Read

Only Memory (EEPROM)

The electrically erasable programmable read only

memory (EEPROM) is a permanent memory chip that is

physically soldered within the ECM. The EEPROM

contains the program and the calibration information that

the ECM needs to control powertrain operation.

Unlike the PROM used in past applications, the EEPROM

is not replaceable. If the ECM is replaced, the new ECM

will need to be programmed. Equipment containing the

correct program and calibration for the vehicle is required

to program the ECM.

Fuel Control Heated Oxygen Sensors

The fuel control heated oxygen sensor is mounted in the

exhaust stream where they can monitor the oxygen

content of the exhaust gas. The oxygen present in the

exhaust gas reacts with the sensor to produce a voltage

output. This voltage should constantly fluctuate from

approximately 100 mV to 900 mV. The heated oxygen

sensor voltage can be monitored with a Tech 2. By

monitoring the voltage output of the oxygen sensor, the

ECM calculates the pulse width command for the

injectors to produce the proper combustion chamber

mixture.

DLow HO2S voltage is a lean mixture which will result in

a rich command to compensate.

DHigh HO2S voltage is a rich mixture which will result in

a lean command to compensate.

0012

Intake Air Temperature (IAT) Sensor

The intake air temperature (IAT) sensor is a thermistor

which changes its resistance based on the temperature of

air entering the engine. Low temperature produces a high

resistance of 100,000 ohms at –40°C (–40°F). High

temperature causes low resistance of 70 ohms at 130°C

(266°F) . The ECM supplies a 5-volt signal to the sensor

through a resistor in the ECM and monitors the signal

voltage. The voltage will be high when the incoming air is

cold. The voltage will be low when the incoming air is hot.

By measuring the voltage, the ECM calculates the

incoming air temperature. The IAT sensor signal is used

to adjust spark timing according to the incoming air

density.

The Tech 2 displays the temperature of the air entering

the engine. The temperature should read close to the

ambient air temperature when the engine is cold and rise

as underhood temperature increases. If the engine has

not been run for several hours (overnight), the IA T sensor

temperature and engine coolant temperature should read

close to each other. A fault in the IAT sensor circuit will set

DTC P0112 or DTC P0113.

060RW034

Mass Air Flow (MAF) Sensor

The mass air flow (MAF) sensor measures the difference

between the volume and the quantity of air that enters the

engine. “Volume” means the size of the space to be filled.

“Quantity” means the number of air molecules that will fit

into the space. This information is important to the ECM

because heavier, denser air will hold more fuel than

lighter, thinner air. The ECM adjusts the air/fuel ratio as

needed depending on the MAF value. The Tech 2 reads

the MAF value and displays it in terms of grams per

second (gm/s). At idle, the Tech 2 should read between

4-7 gm/s on a fully warmed up engine. Values should

change quickly on acceleration. Values should remain

stable at any given RPM. A failure in the MAF sensor or

circuit will set DTC P0101, DTC P0102, or DTC P0103.

060RW023

Barometric Pressure (BARO) Sensor

The barometric pressure (BARO) sensor responds to

changes in intake manifold pressure (vacuum).

DBarometric pressure (BARO).

If the ECM detects a voltage that is lower than the

possible range of the BARO sensor, DTC P0107 will be

set. A signal voltage higher than the possible range of the

sensor will set DTC P0108. The ECM can detect a shifted

BARO sensor. The ECM compares the BARO sensor

signal to a calculated BARO based on throttle position

and various engine load factors.

060RW033

Engine Control Module (ECM)

The engine control module (ECM) is located on the

common chamber. The ECM controls the following:

DFuel metering system.

DIgnition timing.

DOn-board diagnostics for powertrain functions.

The ECM constantly observes the information from

various sensors. The ECM controls the systems that

affect vehicle performance. The ECM performs the

diagnostic function of the system. It can recognize

operational problems, alert the driver through the MIL

(Service Engine Soon lamp), and store diagnostic trouble

codes (DTCs). DTCs identify the problem areas to aid the

technician in making repairs.

ECM Function

The ECM supplies either 5 or 12 volts to power various

sensors or switches. The power is supplied through

resistances in the ECM which are so high in value that a

test light will not light when connected to the circuit. In

some cases, even an ordinary shop voltmeter will not give

an accurate reading because its resistance is too low.

Therefore, a digital voltmeter with at least 10 megohms

input impedance is required to ensure accurate voltage

readings. T ool J 39200 meets this requirement. The ECM

controls output circuits such as the injectors, IAC, cooling

fan relays, etc., by controlling the ground or the power

feed circuit through transistors or through either of the

following:

DOutput Driver Module (ODM)

060RW025

ECM Components

The ECM is designed to maintain exhaust emission levels

to government mandated standards while providing

excellent driveability and fuel efficiency. The ECM

monitors numerous engine and vehicle functions via

electronic sensors such as the throttle position (TP)

sensor, heated oxygen sensor (HO2S), and vehicle

speed sensor (VSS). The ECM also controls certain

engine operations through the following:

DFuel injector control

DIgnition control module

DEvaporative emission (EVAP) purge

DA/C clutch control

ECM Voltage Description

The ECM supplies a buffered voltage to various switches

and sensors. It can do this because resistance in the

ECM is so high in value that a test light may not illuminate

when connected to the circuit. An ordinary shop

voltmeter may not give an accurate reading because the

voltmeter input impedance is too low . Use a 10-megohm

input impedance digital voltmeter (such as

5-8840-0285-0) to assure accurate voltage readings.

The input/output devices in the ECM include

analog-to-digital converters, signal buffers, counters,

and special drivers. The ECM controls most components

with electronic switches which complete a ground circuit

when turned “ON.”

ECM Input/Outputs

Inputs – Operating Conditions Read

DAir Conditioning “ON” or “OFF”

DEngine Coolant Temperature

DCrankshaft Position

DExhaust Oxygen Content

DElectronic Ignition

DBarometric Pressure

DBattery Voltage

DThrottle Position

DVehicle Speed

DFuel Pump Voltage

DPower Steering Pressure

DIntake Air Temperature

DMass Air Flow

DCamshaft Position

Outputs – Systems Controlled

DEVAP Canister Purge

DIgnition Control

DFuel Control

DIdle Air Control

DElectric Fuel Pump

DAir Conditioning

DDiagnostics

– Malfunction Indicator Lamp (Service Engine

Soon lamp)

– Data Link Connector (DLC)

– Data Output

ECM Service Precautions

The ECM is designed to withstand normal current draws

associated with vehicle operation. Avoid overloading any

circuit. When testing for opens and shorts, do not ground

or apply voltage to any of the ECM’s circuits unless

instructed to do so. These circuits should only be tested

using digital voltmeter 5-8840-0285-0. The ECM should

remain connected to the ECM or to a recommended

breakout box.

Throttle Position (TP) Sensor

The throttle position (TP) sensor is a potentiometer

connected to the throttle shaft on the throttle body. The

ECM monitors the voltage on the signal line and

calculates throttle position. As the throttle valve angle is

changed (accelerator pedal moved), the TP sensor signal

also changes. At a closed throttle position, the output of

the TP sensor is low. As the throttle valve opens, the

output increases so that at wide open throttle (WOT), the

output voltage should be above 4 volts.

The ECM calculates fuel delivery based on throttle valve

angle (driver demand). A broken or loose TP sensor may

cause intermittent bursts of fuel from an injector and

unstable idle because the ECM thinks the throttle is

moving. A hard failure in the TP sensor 5-volt reference

or signal circuits will set either a DTC P0122 or DTC

P0123. A hard failure with the TP sensor ground circuit

may set DTC P0123 and DTC P01 12. Once a DTC is set,

the ECM will use an artificial default value based on

engine RPM and mass air flow for the throttle position,

and some vehicle performance will return. A high idle

may result when either DTC P0122 or DTC P0123 is set.

The ECM can detect intermittent TP sensor faults. The

ECM can also detect a shifted TP sensor. The ECM

monitors throttle position and compares the actual TP

sensor reading to a predicted TP value calculated from

engine speed. If the ECM detects an out-of-range

condition, DTC P0121 will be set.

Vehicle Speed Sensor (VSS)

The ECM determines the speed of the vehicle by

converting a plusing voltage signal from the vehicle speed

sensor (VSS) into miles per hour. The ECM uses this

signal to operate the cruise control, speedometer, and the

TCC and shift solenoids in the transmission. For more

information on the TCC and shift solenoids, refer to

4L30-E Automatic Transmission.

0008

Use of Circuit Testing Tools

Do not use a test light to diagnose the powertrain

electrical systems unless specifically instructed by the

diagnostic procedures. Use Connector Test Adapter Kit J

35616 whenever diagnostic procedures call for probing

connectors.

Aftermarket Electrical and Vacuum

Equipment

Aftermarket (add-on) electrical and vacuum equipment is

defined as any equipment which connects to the vehicle’s

electrical or vacuum systems that is installed on a vehicle

after it leaves the factory. No allowances have been

made in the vehicle design for this type of equipment.

NOTE: No add-on vacuum equipment should be added

to this vehicle.

NOTE: Add-on electrical equipment must only be

connected to the vehicle’s electrical system at the battery

(power and ground).

Add-on electrical equipment, even when installed to

these guidelines, may still cause the powertrain system to

malfunction. This may also include equipment not

connected to the vehicle electrical system such as

portable telephones and radios. Therefore, the first step

in diagnosing any powertrain problem is to eliminate all

aftermarket electrical equipment from the vehicle. After

this is done, if the problem still exists, it may be diagnosed

in the normal manner.

Electrostatic Discharge Damage

Electronic components used in the ECM are often

designed to carry very low voltage. Electronic

components are susceptible to damage caused by

electrostatic discharge. Less than 100 volts of static

electricity can cause damage to some electronic

components. By comparison, it takes as much as 4000

volts for a person to feel even the zap of a static

discharge.

TS23793

There are several ways for a person to become statically

charged. The most common methods of charging are by

friction and induction.

DAn example of charging by friction is a person sliding

across a vehicle seat.

DCharge by induction occurs when a person with well

insulated shoes stands near a highly charged object

and momentary touches ground. Charges of the

same polarity are drained off leaving the person

highly charged with the opposite polarity. Static

charges can cause damage, therefore it is important

to use care when handling and testing electronic

components.

NOTE: To prevent possible electrostatic discharge

damage, follow these guidelines:

DDo not touch the ECM connector pins or soldered

components on the ECM circuit board.

DDo not open the replacement part package until the

part is ready to be installed.

DBefore removing the part from the package, ground

the package to a known good ground on the vehicle.

DIf the part has been handled while sliding across the

seat, while sitting down from a standing position, or

while walking a distance, touch a known good ground

before installing the part.

General Description (Air Induction)

Air Induction System

The air induction system filters contaminants from the

outside air, and directs the progress of the air as it is

drawn into the engine. A remote-mounted air cleaner

prevents dirt and debris in the air from entering the

engine. The air duct assembly routes filtered air to the

throttle body. Air enters the engine by to following steps:

1.Through the throttle body.

2.Into the common chamber.

3.Through the cylinder head intake ports.

4.Into the cylinders.

055RV010

General Description (Fuel Metering)

Acceleration Mode

The ECM provides extra fuel when it detects a rapid

increase in the throttle position and the air flow.

Accelerator Controls

The accelerator control system is a cable-type system.

Battery Voltage Correction Mode

When battery voltage is low, the ECM will compensate for

the weak spark by increasing the following:

DThe amount of fuel delivered.

DThe idle RPM.

DIgnition dwell time.

CMP Signal

The ECM uses this signal to determine the position of the

number 1 piston during its power stroke, allowing the

ECM to calculate true sequential multiport fuel injection

(SFI). Loss of this signal will set a DTC P0341. If the CMP

signal is lost while the engine is running, the fuel injection

system will shift to a calculated sequential fuel injection

based on the last fuel injection pulse, and the engine will

continue to run. The engine can be restarted and will run

in the calculated sequential mode as long as the fault is

present, with a 1-in-6 chance of being correct.

Clear Flood Mode

Clear a flooded engine by pushing the accelerator pedal

down all the way. The ECM then de-energizes the fuel

injectors. The ECM holds the fuel injectors de-energized

as long as the throttle remains above 80% and the engine

speed is below 800 RPM. If the throttle position becomes

less than 80%, the ECM again begins to pulse the

injectors “ON” and “OFF,” allowing fuel into the cylinders.

Deceleration Mode

The ECM reduces the amount of fuel injected when it

detects a decrease in the throttle position and the air flow.

When deceleration is very fast, the ECM may cut off fuel

completely for short periods.

Engine Speed/Vehicle Speed/Fuel Disable

Mode

The ECM monitors engine speed. It turns off the fuel

injectors when the engine speed increase above 6400

RPM. The fuel injectors are turned back on when engine

speed decreases below 6150 RPM.

Fuel Cutoff Mode

No fuel is delivered by the fuel injectors when the ignition

is “OFF.” This prevents engine run-on. In addition, the

ECM suspends fuel delivery if no reference pulses are

detected (engine not running) to prevent engine flooding.

Fuel Injector

The sequential multiport fuel injection (SFI) fuel injector is

a solenoid-operated device controlled by the ECM. The

ECM energizes the solenoid, which opens a valve to allow

fuel delivery.

The fuel is injected under pressure in a conical spray

pattern at the opening of the intake valve. Excess fuel not

used by the injectors passes through the fuel pressure

regulator before being returned to the fuel tank.

A fuel injector which is stuck partly open will cause a loss

of fuel pressure after engine shut down, causing long

crank times.

0003

Fuel Metering System Components

The fuel metering system is made up of the following

parts:

DThe fuel injectors.

DThe throttle body.

DThe fuel rail.

DThe fuel pressure regulator.

DThe ECM.

DThe crankshaft position (CKP) sensor.

DThe camshaft position (CMP) sensor.

DThe idle air control (IAC) valve.

DThe fuel pump.

DThe fuel pump relay.

Basic System Operation

The fuel metering system starts with the fuel in the fuel

tank. An electric fuel pump, located in the fuel tank,

pumps fuel to the fuel rail through an in-line fuel filter. The

pump is designed to provide fuel at a pressure above the

pressure needed by the injectors. A fuel pressure

regulator in the fuel rail keeps fuel available to the fuel

injectors at a constant pressure. A return line delivers

unused fuel back to the fuel tank. Refer to

Section 6C

for

further information on the fuel tank, line filter, and fuel

pipes.

Fuel Metering System Purpose

The basic function of the air/fuel metering system is to

control the air/fuel delivery to the engine. Fuel is delivered

to the engine by individual fuel injectors mounted in the

intake manifold near each intake valve.

The main control sensor is the heated oxygen sensor

(HO2S) located in the exhaust system. The HO2S tells

the ECM how much oxygen is in the exhaust gas. The

ECM changes the air/fuel ratio to the engine by controlling

the amount of time that fuel injector is “ON.” The best

mixture to minimize exhaust emissions is 14.7 parts of air

to 1 part of gasoline by weight, which allows the catalytic

converter to operate most efficiently. Because of the

constant measuring and adjusting of the air/fuel ratio, the

fuel injection system is called a “closed loop” system.

The ECM monitors signals from several sensors in order

to determine the fuel needs of the engine. Fuel is

delivered under one of several conditions called “modes.”

All modes are controlled by the ECM.

Fuel Pressure Regulator

The fuel pressure regulator is a diaphragm-operated

relief valve mounted on the fuel rail with fuel pump

pressure on one side and manifold pressure on the other

side. The fuel pressure regulator maintains the fuel

pressure available to the injector at three times

barometric pressure adjusted for engine load. It may be

serviced separate.

If the pressure is too low, poor performance and a DTC

P0131,DTC P0171 or DTC P1171 will be the result. If the

pressure is too high, excessive odor and/or a DTC P0132,

DTC P0172 will be the result. Refer to

Fuel System

Diagnosis

for information on diagnosing fuel pressure

conditions.

0011

Fuel Pump Electrical Circuit

When the key is first turned “ON,” the ECM energizes the

fuel pump relay for two seconds to build up the fuel

pressure quickly. If the engine is not started within two

seconds, the ECM shuts the fuel pump off and waits until

the engine is cranked. When the engine is cranked and

the 58 X crankshaft position signal has been detected by

the ECM, the ECM supplies 12 volts to the fuel pump relay

to energize the electric in-tank fuel pump.

An inoperative fuel pump will cause a “no-start” condition.

A fuel pump which does not provide enough pressure will

result in poor performance.

Fuel Rail

The fuel rail is mounted to the top of the engine and

distributes fuel to the individual injectors. Fuel is

delivered to the fuel inlet tube of the fuel rail by the fuel

lines. The fuel goes through the fuel rail to the fuel

pressure regulator. The fuel pressure regulator maintains

a constant fuel pressure at the injectors. Remaining fuel

is then returned to the fuel tank.

055RV009

Idle Air Control (IAC) Valve

The purpose of the idle air control (IAC) valve is to control

engine idle speed, while preventing stalls due to changes

in engine load. The IAC valve, mounted in the throttle

body, controls bypass air around the throttle plate. By

moving the conical valve (pintle) in (to decrease air flow)

or out (to increase air flow), a controlled amount of air can

move around the throttle plate. If the RPM is too low , the

ECM will retract the IAC pintle, resulting in more air

moving past the throttle plate to increase the RPM. If the

RPM is too high, the ECM will extend the IAC pintle,

allowing less air to move past the throttle plate,

decreasing the RPM.

The IAC pintle valve moves in small steps called counts.

During idle, the proper position of the IAC pintle is

calculated by the ECM based on battery voltage, coolant

temperature, engine load, and engine RPM. If the RPM

drops below a specified value, and the throttle plate is

closed, the ECM senses a near-stall condition. The ECM

will then calculate a new IAC pintle valve position to

prevent stalls.

If the IAC valve is disconnected and reconnected with the

engine running, the idle RPM will be wrong. In this case,

the IAC must be reset. The IAC resets when the key is

cycled “ON” then “OFF.” When servicing the IAC, it

should only be disconnected or connected with the

ignition “OFF.”

The position of the IAC pintle valve affects engine start-up

and the idle characteristics of the vehicle. If the IAC pintle

is fully open, too much air will be allowed into the manifold.

This results in high idle speed, along with possible hard

starting and a lean air/fuel ratio. DTC P1509 may set. If

the IAC pintle is stuck closed, too little air will be allowed in

the manifold. This results in a low idle speed, along with

possible hard starting and a rich air/fuel ratio. DTC P1508

may set. If the IAC pintle is stuck part-way open, the idle

may be high or low and will not respond to changes in the

engine load.

060RW115

Run Mode

The run mode has the following two conditions:

DOpen loop

DClosed loop

When the engine is first started the system is in “open

loop” operation. In “open loop,” the ECM ignores the

signal from the heated oxygen sensor (HO2S). It

calculates the air/fuel ratio based on inputs from the TP,

ECT, and MAF sensors.

The system remains in “open loop” until the following

conditions are met:

DThe HO2S has a varying voltage output showing that

it is hot enough to operate properly (this depends on

temperature).

DThe ECT has reached a specified temperature.

DA specific amount of time has elapsed since starting

the engine.

DEngine speed has been greater than a specified RPM

since start-up.

The specific values for the above conditions vary with

different engines and are stored in the programmable

read only memory (PROM). When these conditions are

met, the system enters “closed loop” operation. In

“closed loop,” the ECM calculates the air/fuel ratio

(injector on-time) based on the signal from the HO2S.

This allows the air/fuel ratio to stay very close to 14.7:1.

Starting Mode

When the ignition is first turned “ON,” the ECM energizes

the fuel pump relay for two seconds to allow the fuel pump

to build up pressure. The ECM then checks the engine

coolant temperature (ECT) sensor and the throttle

position (TP) sensor to determine the proper air/fuel ratio

for starting.

The ECM controls the amount of fuel delivered in the

starting mode by adjusting how long the fuel injectors are

energized by pulsing the injectors for very short times.

Throttle Body Unit

The throttle body has a throttle plate to control the amount

of air delivered to the engine. The TP sensor and IAC

valve are also mounted on the throttle body. Vacuum

ports located behind the throttle plate provide the vacuum

signals needed by various components.

Engine coolant is directed through a coolant cavity in the

throttle body to warm the throttle valve and to prevent

icing.

060RW063

General Description (Electronic

Ignition System)

Camshaft Position (CMP) Sensor

The camshaft position (CMP) sensor is located on the

timing cover near the camshaft sprocket. As the

camshaft sprocket turns, a magnet in the sprocket

activates the Hall-effect switch in the CMP sensor. When

the Hall-effect switch is activated, it grounds the signal

line to the ECM, pulling the camshaft position sensor

signal circuit’s applied voltage low. This is a CMP signal.

The CMP signals is created as piston #1 is approximately

25° after top dead counter on the power stroke. If the

correct CMP signal is not received by the ECM, DTC

P0341 will be set.

0014

Crankshaft Position (CKP) Sensor

The crankshaft position (CKP) sensor provides a signal

used by the engine control module (ECM) to calculate the

ignition sequence. The sensor initiates the 58X reference

pulses which the ECM uses to calculate RPM and

crankshaft position. Refer to

Electronic Ignition System

for additional information.

Electronic Ignition

The electronic ignition system controls fuel combustion

by providing a spark to ignite the compressed air/fuel

mixture at the correct time. To provide optimum engine

performance, fuel economy, and control of exhaust

emissions, the ECM controls the spark advance of the

ignition system. Electronic ignition has the following

advantages over a mechanical distributor system:

DNo moving parts.

DLess maintenance.

DRemote mounting capability.

DNo mechanical load on the engine.

DMore coil cooldown time between firing events.

DElimination of mechanical timing adjustments.

DIncreased available ignition coil saturation time.

0013

Ignition Coils

A separate coil-at-plug module is located at each spark

plug. The coil-at-plug module is attached to the engine

with two screws. It is installed directly to the spark plug by

an electrical contact inside a rubber boot. A three-way

connector provides 12-volt primary supply from the

15-amp ignition fuse, a ground-switching trigger line from

the ECM, and a ground.

060RW117

Ignition Control

The ignition control (IC) spark timing is the ECM’s method

of controlling the spark advance and the ignition dwell.

The IC spark advance and the ignition dwell are

calculated by the ECM using the following inputs:

DEngine speed.

DCrankshaft position.

DCamshaft position (CMP) sensor.

DEngine coolant temperature (ECT) sensor.

DThrottle position (TP) sensor.

DPark/Neutral position (PRNDL input).

DVehicle speed (vehicle speed sensor).

DECM and ignition system supply voltage.

DThe crankshaft positron (CKP) sensor sends the

ECM a signal related to the exact position of the

crankshaft.

TS22909

DThe camshaft position (CMP) sensor sends a signal

related to the position of the camshaft.

Based on these sensor signals and engine load

information, the ECM sends 5V to each ignition coil.

The ECM applies 5V signal voltage to the ignition coil

requiring ignition. This signal sets on the power transistor

of the ignition coil to establish a grounding circuit for the

primary coil, applying battery voltage to the primary coil.

At the ignition timing, the ECM stops sending the 5V

signal voltage. Under this condition the power transistor

of the ignition coil is set off to cut the battery voltage to the

primary coil, thereby causing a magnetic field generated

in the primary coil to collapse. On this moment a line of

magnetic force flows to the secondary coil, and when this

magnetic line crosses the coil, high voltage induced by

the secondary ignition circuit to flow through the spark

plug to the ground.

TS24047

Ignition Control ECM Output

The ECM provides a zero volt (actually about 100 mV to

200 mV) or a 5-volt output signal to the ignition control (IC)

module. Each spark plug has its own primary and

secondary coil module (”coil-at-plug”) located at the spark

plug itself. When the ignition coil receives the 5-volt signal

from the ECM, it provides a ground path for the B+ supply

to the primary side of the coil-at -plug module. This

energizes the primary coil and creates a magnetic field in

the coil-at-plug module. When the ECM shuts off the

5-volt signal to the ignition control module, the ground

path for the primary coil is broken. The magnetic field

collapses and induces a high voltage secondary impulse

which fires the spark plug and ignites the air/fuel mixture.

The circuit between the ECM and the ignition coil is

monitored for open circuits, shorts to voltage, and shorts

to ground. If the ECM detects one of these events, it will

set one of the following DTCs:

DP0351: Ignition coil Fault on Cylinder #1

DP0352: Ignition coil Fault on Cylinder #2

DP0353: Ignition coil Fault on Cylinder #3

DP0354: Ignition coil Fault on Cylinder #4

DP0355: Ignition coil Fault on Cylinder #5

DP0356: Ignition coil Fault on Cylinder #6

Engine Control Module (ECM)

The ECM is responsible for maintaining proper spark and

fuel injection timing for all driving conditions. To provide

optimum driveability and emissions, the ECM monitors

the input signals from the following components in order

to calculate spark timing:

DEngine coolant temperature (ECT) sensor.

DIntake air temperature (IAT) sensor.

DMass air flow (MAF) sensor.

DPRNDL input from transmission range switch.

DThrottle position (TP) sensor.

DVehicle speed sensor (VSS) .

DCrankshaft position (CKP) sensor.

Spark Plug

Although worn or dirty spark plugs may give satisfactory

operation at idling speed, they frequency fail at higher

engine speeds. Faulty spark plugs may cause poor fuel

economy, power loss, loss of speed, hard starting and

generally poor engine performance. Follow the

scheduled maintenance service recommendations to

ensure satisfactory spark plug performance. Refer to

Maintenance and Lubrication

Normal spark plug operation will result in brown to

grayish-tan deposits appearing on the insulator portion of

the spark plug. A small amount of red-brown, yellow, and

white powdery material may also be present on the

insulator tip around the center electrode. These deposits

are normal combustion by-products of fuels and

lubricating oils with additives. Some electrode wear will

also occur. Engines which are not running properly are

often referred to as “misfiring.” This means the ignition

spark is not igniting the air/fuel mixture at the proper time.

Spark plugs may also misfire due to fouling, excessive

gap, or a cracked or broken insulator. If misfiring occurs

before the recommended replacement interval, locate

and correct the cause.

Carbon fouling of the spark plug is indicated by dry, black

carbon (soot) deposits on the portion of the spark plug in

the cylinder. Excessive idling and slow speeds under

light engine loads can keep the spark plug temperatures

so low that these deposits are not burned off. Very rich

fuel mixtures or poor ignition system output may also be

the cause. Refer to DTC P0172.

Oil fouling of the spark plug is indicated by wet oily

deposits on the portion of the spark plug in the cylinder,

usually with little electrode wear . This may be caused by

oil during break-in of new or newly overhauled engines.

Deposit fouling of the spark plug occurs when the normal

red-brown, yellow or white deposits of combustion by

products become sufficient to cause misfiring. In some

cases, these deposits may melt and form a shiny glaze on

the insulator around the center electrode. If the fouling is

found in only one or two cylinders, valve stem clearances

or intake valve seals may be allowing excess lubricating

oil to enter the cylinder, particularly if the deposits are

heavier on the side of the spark plug facing the intake

valve.

TS23995

Excessive gap means that the air space between the

center and the side electrodes at the bottom of the spark

plug is too wide for consistent firing. This may be due to

improper gap adjustment or to excessive wear of the

electrode during use. A check of the gap size and

comparison to the gap specified for the vehicle in

Maintenance and Lubrication

will tell if the gap is too wide.

A spark plug gap that is too small may cause an unstable

idle condition. Excessive gap wear can be an indication

of continuous operation at high speeds or with engine

loads, causing the spark to run too hot. Another possible

cause is an excessively lean fuel mixture.

TS23992

Low or high spark plug installation torque or improper

seating can result in the spark plug running too hot and

can cause excessive center electrode wear. The plug

and the cylinder head seats must be in good contact for

proper heat transfer and spark plug cooling. Dirty or

damaged threads in the head or on the spark plug can

keep it from seating even though the proper torque is

applied. Once spark plugs are properly seated, tighten

them to the torque shown in the Specifications T able. Low

torque may result in poor contact of the seats due to a

loose spark plug. Overtightening may cause the spark

plug shell to be stretched and will result in poor contact

between the seats. In extreme cases, exhaust blow-by

and damage beyond simple gap wear may occur.

Cracked or broken insulators may be the result of

improper installation, damage during spark plug

re-gapping, or heat shock to the insulator material. Upper

insulators can be broken when a poorly fitting tool is used

during installation or removal, when the spark plug is hit

from the outside, or is dropped on a hard surface. Cracks

in the upper insulator may be inside the shell and not

visible. Also, the breakage may not cause problems until

oil or moisture penetrates the crack later.

TS23994

A broken or cracked lower insulator tip (around the center

electrode) may result from damage during re-gapping or

from “heat shock” (spark plug suddenly operating too

hot).

TS23993

DDamage during re-gapping can happen if the gapping

tool is pushed against the center electrode or the

insulator around it, causing the insulator to crack.

When re-gapping a spark plug, make the adjustment

by bending only the ground side terminal, keeping the

tool clear of other parts.

D”Heat shock” breakage in the lower insulator tip

generally occurs during several engine operating

conditions (high speeds or heavy loading) and may be

caused by over-advanced timing or low grade fuels.

Heat shock refers to a rapid increase in the tip

temperature that causes the insulator material to

crack.

Spark plugs with less than the recommended amount of

service can sometimes be cleaned and re-gapped , then

returned to service. However , if there is any doubt about

the serviceability of a spark plug, replace it. Spark plugs

with cracked or broken insulators should always be

replaced.

A/C Clutch Diagnosis

A/C Clutch Circuit Operation

A 12-volt signal is supplied to the A/C request input of the

ECM when the A/C is selected through the A/C control

switch.

The A/C compressor clutch relay is controlled through the

ECM. This allows the ECM to modify the idle air control

position prior to the A/C clutch engagement for better idle

quality. If the engine operating conditions are within their

specified calibrated acceptable ranges, the ECM will

enable the A/C compressor relay. This is done by

providing a ground path for the A/C relay coil within the

ECM. When the A/C compressor relay is enabled,

battery voltage is supplied to the compressor clutch coil.

The ECM will enable the A/C compressor clutch

whenever the engine is running and the A/C has been

requested. The ECM will not enable the A/C compressor

clutch if any of the following conditions are met:

DThe throttle is greater than 90%.

DThe engine speed is greater than 6315 RPM.

DThe ECT is greater than 119°C (246°F).

DThe IAT is less than 5°C (41°F).

DThe throttle is more than 80% open.

A/C Clutch Circuit Purpose

The A/C compressor operation is controlled by the engine

control module (ECM) for the following reasons:

DIt improvises idle quality during compressor clutch

engagement.

DIt improvises wide open throttle (WOT) performance.

DIt provides A/C compressor protection from operation

with incorrect refrigerant pressures.

The A/C electrical system consists of the following

components:

DThe A/C control head.

DThe A/C refrigerant pressure switches.

DThe A/C compressor clutch.

DThe A/C compressor clutch relay.

DThe ECM.

A/C Request Signal

This signal tells the ECM when the A/C mode is selected

at the A/C control head. The ECM uses this to adjust the

idle speed before turning on the A/C clutch. The A/C

compressor will be inoperative if this signal is not

available to the ECM.

Refer to

A/C Clutch Circuit Diagnosis

for A/C wiring

diagrams and diagnosis for A/C electrical system.

General Description (Evaporative

(EVAP) Emission System)

EVAP Emission Control System Purpose

The basic Evaporative Emission (EVAP) Control System

used on all vehicle is the charcoal canister storage

method. This method transfers fuel vapor from the fuel

tank to an activated carbon (charcoal) storage device

(canister) to hold the vapors when the vehicle is not

operating. When the engine is running, the fuel vapor is

purged from the carbon element by intake air flow and

consumed in the normal combustion process.

Vapor Canister

Gasoline vapors from the fuel tank flow into the tube

labeled tank. Any liquid fuel goes into a reservoir in the

bottom of the canister to protect the integrity of the carbon

bed above. These vapors are absorbed into the carbon.

The canister is purged when the engine is running or

commanded by Engine Control Module (ECM). Ambient

air is allowed into the canister through the air tube in the

top. The air mixes with the vapor and the mixture is drawn

into the intake manifold.

Evap Control System

The solenoid used with this canister uses V acuum Switch

Valve to control purge. The ECM opens and closes the

solenoid to control purge.

The ECM energizes the solenoid valve and allows purge

when:

DEngine is warm above 69°C (156°F).

DAfter the engine has been running a specified time.

060RW118

Legend

(1) Vapor from Fuel Tank

(2) Evaporate Emission Canister Purge Vacuum

(3) Canister Body

(4) Carbon

(5) Filter

(6) Grid

(7) Air Flow During Purge

DThrottle position is above 7% throttle position sensor .

Results of Incorrect Operation

Poor idle, stalling and poor driveability can be caused by:

DInoperative purge solenoid.

DDamaged canister.

DHoses split, cracked and/or not connected to the

proper tubes.

Evidence of fuel loss or fuel vapor odor can be caused by:

DLiquid fuel leaking from fuel lines, or fuel pump.

DCracked or damaged canister.

DDisconnected, misrouted, kinked, deteriorated or

damaged vapor hoses, or control hoses.

If the solenoid is always open, the canister can purge to

the intake manifold at all times. This can allow extra fuel at

idle or during warm-up, which can cause rough or

unstable idle, or too rich operation.

If the solenoid is always closed, the canister can become

over-loaded, resulting in fuel odor.

Diagnosis

060RW113

Legend

(1) Throttle Body

(2) Fuel Vapor Purge Control Solenoid

(3) Fuel Vapor Canister

(4) Check and Relief Valve

(5) Fuel Tank

(6) Pressure/Vacuum Vented

(7) Rollover Valve

Visual Check of Canister

Cracked or damaged, replace canister.

Evaporate Emission Canister Purge Valve Check

060RW108

Circuit Description:

Evaporate emission canister purge is controlled by a

solenoid that allows manifold and/or ported vacuum to

purge the canister when energized. The Engine Control

Module (ECM) supplies a ground to energize the solenoid

(purge “ON”). The purge solenoid control by the ECM is

turned “;ON” or “;OFF” under specific engine conditions.

The purge solenoid is turned “;ON” when all of the

following conditions are met.

DData link connector is ungrounded.

DEngine run time after start more than 20 seconds.

DEngine coolant temperature above 60°C.

DVehicle speed is above 9 mile per hour.

Also, if the diagnostic test terminal is grounded with the

engine stopped, the purge solenoid is energized (purge

“ON”).

Test Description:

Numbers below refer to circled numbers on the diagnostic

chart.

1.Check to see if the solenoid is opened or closed. The

solenoid is normally de-energized in this step, so it

should be closed.

2.Check to determine if solenoid was open due to

electrical CKT problem or defective solenoid.

3.Completes functional check by grounding test

terminal. This should normally energize the solenoid

opening the valve which should allow the vacuum to

drop (purge “ON”).

Diagnostic Aids:

Make a visual check of vacuum hose(s). Check throttle

body for possible cracked, or plugged vacuum block.

Malfunction indicator lamp for possible mechanical

problem.

Special Tools

901RW180

Legend

(1) PCMCIA Card

(2) RS232 Loop Back Connector

(3) SAE 16/19 Adapter

(4) DLC Cable

(5) TECH 2

ILLUSTRATION TOOL NO.

TOOL NAME

5–8840–0285–0

(J 39200)

High Impedance Multi-

meter (Digital Voltmeter

– DVM)

(1) PCMCIA Card

(2) RS232 Loop Back

Connector

(3) SAE 16/19 Adapter

(4) DLC Cable

(5) TECH 2

5–8840–0607–0

(J 34142-B)

Unpowered Test Light

5–8840–0385–0

(J 35616-A/BT-8637)

Connector Test Adapter

Kit

5–8840–0383–0

(J 26792/BT-7220-1)

Spark Tester

5–8840–0378–0

(J 34730-E)

Port Fuel Injection Diag-

nostic Kit

ILLUSTRATION TOOL NO.

TOOL NAME

5–8840–2312–0

(J 37027-A)

IAC Motor Analyzer

5–8840–0279–0

(J 23738-A)

Vacuum Pump with

Gauge

5–8840–2640–0

(J 39194-B)

Heated Oxygen Sensor

Wrench

5–8840–0632–0

(J 35689-A)

Terminal Remover

5–8840–0388–0

(J 28742-A)

Weather Pack II Termi-

nal Remover

5–8840–2635–0

(J 39021-90)

Injector Switch Box

ILLUSTRATION TOOL NO.

TOOL NAME

5–8840–2636–0

(J 39021-65)

Injector Test Light

5–8840–2607–0

(J 41413)

EVAP Pressure/Purge

Diagnostic Station

5–8840–2608–0

(J 41416)

Ultrasonic Leak Detec-

tor

1.5–8840–2607–0 (J 41413) EVAP Pressure/Purge

Diagnostic Station is a multipurpose tool which is

used to perform several diagnostic procedures for

enhanced emission testing. The station will

accommodate a nitrogen gas filled cylinder which is

used to pressurize the vehicle EVAP system for a

leakdown test and leak location test when a vehicle is

repaired for leakage in the enhanced evaporative

emission control system. It also has two additional

gauges (inches of mercury and inches of water) which

are used to measure both source vacuum and EVAP

canister purge vacuum to verify correct operation and

vapor flow within the canister purge circuit.

2.5–8840–2608–0 (J 41416) Ultrasonic Leak Detector

is a microprocessor-based device used to detect

leaks in the enhanced evaporative emission control

system. The evaporative system is pressurized to 30

inches of water using the 5–8840–2607–0 (J 41413)

EVAP Pressure/Purge Diagnostic System. Small

leaks in the EVAP system will emit sound at a high

frequency undetectable by a human ear but

detectable with the 5–8840–2608–0 (J 41416). The

technician traces along the evaporative system and

can pinpoint leaks due to corroded lines, cracked

hoses, or a damaged EVAP component. The

detector includes a high quality set of headphones to

block out surrounding shop noise and the LED

sensitivity meter allows a visual reference for locating

leaks in conjunction with the audio output heard

through the headphones. Powered by (1) nine volt

battery.