SECTI ON 6C 3-1 - GENERAL INFORMATI ON -

GEN III V8 ENGINE

CAUTION:

This vehicle will be equipped with a Supplemental Restraint System (SRS). A SRS will consist of either

seat belt pre-tensioners and a driver's air bag, seat belt pre-tensioners and a driver's and front

passenger's air bags or seat belt pre-tensioners, driver’s and front passenger’s air bag and left and right

hand side air bags. Refer to SAFETY PRECAUTIONS, Section 12M Supplemental Restraint System of the

VT Series II Service Information before performing any service operation on, or around any SRS

components, the steering mechanism or wiring. Failure to follow the SAFETY PRECAUTIONS could result

in SRS deployment, resulting in possible personal injury or unnecessary SRS system repairs.

1. GENERAL DESCRIPTION

The engine used in this vehicle uses an Powertrain Control Module (PCM) to control exhaust emissions while

maintaining excellent driveability and fuel economy. The PCM maintains a desired air/fuel ratio at precisely

14.7 to 1. To maintain a 14.7 to 1 air fuel ratio the PCM m onitors the output signal from two oxygen sensors. The

PCM will either add or subtract fuel pulses based on the oxygen sensors output signal. This method of feed back

fuel control is called CLOSED LOOP.

In addition to fuel cont rol, the PCM also c ontrols the f ollowing systems.

• The ignition dwell

• The ignition timing

• The idle speed

• The engine elec tric cooling fan

• The fuel pump

• The instrument panel Check Powertr ain Lamp (CPL)

• The A / C compress or clu t c h

• The automatic transmission functions

The PCM also interfaces with other vehicle control modules, such as the Powertrain Interface Module (PIM), trip

com put er an d Body Contro l Module ( BC M). Th e f ollowing diagr am con tains a list of the vario us op era ting c ondit ions

sensed by the PCM, and the various systems controlled. Details of basic operation, diagnosis, and service are

covered in this Section.

The PCM has a built-in diagnostic system that identifies operational problems and alerts the driver by illuminating

the Check Powertrain Lamp (CPL) on the instrument panel. If the lamp illuminates while driving, it does not mean

that the engine should be stopped imm ediately, but the cause of the lam p illuminating should be checked as soon

as is reas onably possible. Th e PCM h as built in bac k-u p system s t hat in all but the m os t severe fa ults will allow the

vehicle to operate in a near normal manner un til repair s can be made.

Below the instrument panel is a Data Link Connector (DLC) which is used by the assembly plant for a computer

check-out of the powertrain management system. The DLC is also used in service to help diagnose the system.

Refer to Section 6C3 -2 , DIAGNOSIS in this Section for further details.

Techline

Not e:

Some parameters may travel through one or more controllers for input or output controls.

ENGINE CONTROLS

TRANSMISSION CONTROLS

PCM Operating Conditions Sensed and Systems Controlled

• A/C Pressur e Sensor

• A/C Request "ON" or "OFF"

• Battery Voltage

• Camshaft Po sitio n (CMP)

• Crankshaft Position (CKP)

• DLC Da ta Stream Input

• Engine Coolant Level Switch

• Engine Coolant Temperature (ECT)

• Engine Cooling Fan Response

• Engine Knock (KS)

• Engine Speed (RPM)

• Exhaust Gas Oxygen Cont ent

• Intake A ir T emp era ture (IAT)

• Mass Air Flow (MAF)

• Manifold Abs olute Pre ssure (MAP)

• Oil Pressure Sensor

• Spark Retard Signal

• Stop Lamp Switch

• Thrott l e Positio n ( TP)

• Transmission Gear Position

• Th eft D et errent Signal

• Vehic l e Speed (VSS)

POWERTRAIN

CONTROL

MODULE (P CM)

• Air Conditioning Compressor Clutch

• Canister Purge Solenoid

• Diagnostics

• - Check Powertrain Lamp (CPL)

• - DLC Data Stream Output

• - Field Service Mode

• El ectric Engi n e Cooling Fa n

• Electron i c Spark Con t ro l (ESC)

• Electron ic Spark Timing (EST)

• Fuel C ontrol

- Fuel Injectors

- Fuel Pump

• Idle A ir Cont rol

• Torque Management

OPERATING PA RAMETERS SENSED SYS TEMS CONT RO L L E D

• Battery Voltage

• Economy/ Power Switch

• Engine Speed (Engine RPM)

• Engine Coolant Temperature (ECT)

• Stop Lamp Switch

• Throttle Position (TP Sensor)

• Transmission Fluid Temperature (TFT)

• Transmission Gear Position

• Vehicle Spee d Sensor (VSS)

• Transmission Fluid Pressure (TFP)

• Switch Assembly

• TCC Enable Solenoid

• 3-2 Shift Solenoid

• 1-2 Shift Solenoid

• 2-3 Shift Solenoid

• Diagnostics

• - Check Powertrain Lamp (CPL)

• - DLC Data Stream Out pu t

• - Field Service Mode

POWERTRAIN

CONTROL

MODULE (P CM)

OPERATING PA RAMETERS SENSED SYSTEM CONTROLLED

POWERTRAIN

INTERFACE

MODULE (P IM)

POWERTRAIN

INTERFACE

MODULE (PIM)

BODY

CONTROL

MODULE (B CM)

BODY

CONTROL

MODULE (BCM)

T26C3001

151617 18

20 21

Componen t Lo cations View GEN III V8 Engi ne

1. Engi ne Compar t m ent Fusi ble Link Housing

2. Battery Harness Fusible Link Housing

3. Engi ne Compartment Rel ay Housing

4. Engi ne Compartment Rel ay Housing

5. Fuel Pressure Regulator (in Fuel Tank)

6. A/C Accumulator Tank

7. Brake Hydraulic Failure Switch

8. Fuel Injectors (8)

9. Idle Air Control (IAC) Valve

10. Check Powertrain Lamp (CPL)

11. Ignition Coil/Module Right Bank

12. Ignition Coil/Module Left Bank

13. Engine Fa ns (2)

14. Canis ter Purge Solenoid

15. Mass Air Flow (MAF) Sensor

16. Engine Coolant Temperature (ECT) Sensor

17. Throttle P osition (TP ) Se nsor

18. Intak e Ai r Temperature (IAT) Sensor

19. Vehicle Speed Sensor (VSS)

20. Camshaft Position (CMP) Sensor

21. Heated Oxygen (HO2S) Sensor (2)

22. Crankshaft Position (CKP) Sensor

23. Knock Sensors (KS) (2)

24. ECC In - Car Air Temperature Sensor

25. A/C Refrigerant Pressure Transducer

26. Powertrain Control Module (PCM)

27. Powertrain Interface Module (PIM) - Inside

vehicle behind left kick panel

28. Diagnostic Link Connector (DLC)

29. Oil Pressure Sensor

30. Manifold Absolute Pressure (MAP) Sensor

A Battery

B ABS

C BCM

D Fuel Tank

E Surge Tank (With Low Coolant Level Switch)

F Air Cleaner

GEN III V8 Engine View Left-Hand Side

1. Right -Hand Ignition Coils/Mod ul es

2. Fuel Pu l se Dampe ner

3. Fuel Rail with Injectors

4. Evaporative Canister Purge Solenoid

5. Crankcase Vent

6. Left-Hand Ignition Coils/Modules

7. Engine Coolant Temperature (ECT) Sensor

8. Fuel Pr essure Gauge Test Co nnector

9. Throttle Position (TP) Sensor

10. Idle Air Control (IAC) Valve

11. Throttle Body

GEN III V8 Engine Front View

1. Idle Air Contro l (IAC) Valve

2. Throttle Position (TP) Sensor

3. Generator

4. Throttle Body

GEN III V8 Engine Rear View

1. Manifold Absolute Pressure (MAP) Sensor

2. Cams haft Posi tion (CMP) Sensor

3. Oil Pressure Sensor

4. Connector to Knock Sensor Jumper Harness

Au to m atic Tran s m iss i o n Internal Electr on ic Co m po n en t Lo ca tions

1. Vehicle Speed Sensor (VSS)

2. Shift So l enoid B (SS) Valve

3. Shift So l enoid A (SS) Valve

4. Autom atic Tra nsmission Fluid Pres sure (TFP) Manual Valve Position Switch

5. Shift Solenoid (SS) Valve Assembly

6. To rque Converter Clutch Pulse Width Modulation (TCC PWM) Solenoid Valve

7. Torque Converter Clu tch (TCC) Solenoid Val ve

8. Pressure Control Solenoid (PCS) Valve

Engine Compa rt m ent Fuse/Re l ay Panel

1. Fan 1 Fusible Link FU 15. Start Relay

2. Fan 2 Fusible Link FT 16. Headlamp High Beam Relay

3. Engine Fan Relay (Low Speed) 17. Fuel Pump Relay

4. Lighting Fusible Link FQ 18. Front Wiper Relay

5. ABS Fusible Link FR 19. Headlamp Low Beam Relay

6. Engine Fusible Link FS 20. Injectors / Ignition Fuse F35

7. Main Fusible Link FJ 21. Injectors / Ignition Fuse F34

8. Blower Fusible Link FY 22. Engine Sensors Fuse F33

9. Engine Cont. (EF I) Rel ay 23. Automatic Transmission Fuse F32

10. Horn Relay 24. Engine Control / BCM Fuse F31

11. A/C Relay 25. LH Headl am p Fuse F30

12. Theft Horn Relay 26. RH Headlamp Fu se F29

13. Fog Lamp Relay 27. Fuel Pump Fuse F28

14. Engine Fan Relay (High Speed) 28. Throttle Relaxer Control Module Fuse F36

1.1 POWERTRAIN CONTROL MODULE (PCM)

The Powert ra in Con tr ol Module (P CM), is loc ated in

the engine compartment. The PCM is the control

centr e of the vehicle. It controls the following:

• Fuel metering system.

• Transmission shifting.

• Igni tion timing.

• Knock Sensor (KS) .

• Evaporative Emission Control System (EECS)

Purge.

• Cooling fan.

• A/C system.

• Che c k P owe rtrain L amp (CPL).

• Theft Deterrent (Injector control).

The PCM constantly monitors the information from

various sensors, and controls the systems that

affect vehicle performance. The PCM also

performs diagnostic function of the system. It can

recognise operational problems. The PCM also

alerts the driver through the Check Powertrain

Lamp (CPL) via the Class II serial data

communication line to the Powertrain Interface

Module (PIM). This is where the PIM converts the

Class II serial data communication to Universally

Asynchronous Receiving/T ransmitting (UART).

This UART serial data communication is then sent

from the PIM to the Body Control Module (BCM)

then from the BCM to t he Inst ru ment Panel Clu st er.

When the PCM detects a malfunction, it stores a

Diagnos tic Trouble Code (DTC ) .

GEN3 0004

Pow ertrain Control Module

1. Connector J1 BLUE

2. Connector J2 RED

A stored DTC, will identify the problem areas. This

will aid the technician in making repairs.

The PCM supplies either 5.0 or 12.0 volts to power

various sensors or switches. This is done through

resis tance in the PCM. The r esistance is s o h igh in

value that a test lamp will not illuminate 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.

Ther efore , a digit al mu ltimeter DMM ( J 3920 0) with

at lea st 10 m egaohm s input im pedance is required

to ensure accurate voltage readings.

The PCM controls output circuits such as the

injec tors , IAC, cooling fan r elays , etc. by controlling

the earth or the power feed circuits through

transistors or a device called an Output Driver

Module (ODM).

GEN3 0005

Pow ertrain Control Module

1. Coolant Surge T ank

2. Powertrain Control Module (PCM)

SERIAL DATA COMMUNICATIONS

Serial data is a series of rapidly changing voltage

signals pulsed from high to low. These signals are

typically 5 volts (UART), 7 volts (Class II ) , and 12 or

0 volts (high or low) and are transmitted through a

wire often referr ed to as the Serial Data Cir c uit.

Today’s automotive regulations require that all

automobile manufacturers establish a common

communications system. Class II communication

was selected as the automotive communication

standard.

The GEN III V8 Engine on-vehicle controllers

communicate with both types of se r ial data:

• Universal Asynchronous Receive and Transm it

(UART)

• Class II

UART serial data has been used for many years

(since the beginning of computer control systems

on GM vehicles). With UART serial data,

controlle rs com m unicate o n a single wire by pulling

the voltage on the data circuit low to create

m essages . As a re sult, when c om munic ation is not

occurring, the signal voltage on the data circuit

rem ains high (usually 5 volts).

Class II serial data takes the signal voltage low

when communication is not occurring. Class II

communication differs from UART in 2 main ways.

1. High is 7 volts.

Serial Data Voltage Signal s

2. The signal uses several pulse widths,

compar ed to UART’s fix ed pulse width.

With a variable pulse width, Class II comm unication

saves switching time in its messages. Class II only

needs to lengthe n the voltage duration and anot her

bit can be sent. Class II supports the transmission

of 10,400 bits per second, compared to UART at

8,192 bits per second. This allows Class II

communication between controllers to be more

complex and quicker.

The most significant result of this Class II

communication is that it provides scan tool

m anufact urers with the ca pability of acc essin g data

fr om any make or model vehicle.

For the PCM Class II communication to interface

between all the other vehicle system controllers, a

Powertrain Inter fac e Module ( PIM) has been adde d

as a com munic ation tr anslator fo r UART and Class

II. For further information on the PIM, refer to

Section 1.2 Powertrain Interface Module (PIM ) in

this Sec tion.

THE DIAGNOSTIC EXECUT IVE

The Diagnostic Executive is a unique segment of

the PCM software which is designed to coordinate

and prioritise the diagnostic procedures as well as

define the protocol for recording and displaying

their results. The main responsibilities of the

Diagnos tic Executive are:

• Monitoring the Diagnostic Test Enabling

Conditions

• Requesting the Check Powertrain Lamp (CPL).

• Recording Pending, Current, and History

DTC(s)

• Storing and Erasing Freeze Frame Data

• Monitoring and Recording Test Status

information.

PCM PROGRAMMING

The PCM for this vehicle application does not

contain a removable PROM, instead it uses an

EEPROM (Flash Memory) which is non rem ovable.

From the f actory, the PCM is progr amm ed with the

proper calibrations for vehicle operation. In the

event that the PCM is replaced, or an updated

calibration is required to correct a vehicle's

operating condition, the new PCM or the new

calibration will require the use of the Tech 2 scan

tool for down loading to the EEPROM (Flash

Memory). Down loading is accomplished through

the vehicle Data Link Connector (DLC) using the

Tech 2 scan tool.

The service replacement PCM EEPROM (Flash

Memory) will not be programmed. DTC P0601 and

P0602 indicates the Flash Memory is not

program med or has m alfunc tioned.

Refer to Section 6 C3-3 SERVICE OPERATIONS –

GEN III V8 Engine in this Section for this service

program ming procedure.

PCM / PIM/BC M SECURITY LINK

Once the PCM, PIM or BCM has been replaced,

the new module(s) must be security linked to each

other . If the pr ocedure is not perf orm ed, th e engin e

will not crank or run.

This linking procedure is found under the BODY

CONTROL MODULE of TECH 2 and has to be

performed as follow s:

Connect TECH 2 to DLC and select:

Diagnostic / (X) 1999 / VT Commodore / Body /

Body Control Module / Security / BCM Link to

PCM/PIM.

The procedu re ”BCM Link to PCM/PIM” will first ask

to select the installed engine. If Gen III V8 is

selected a TIS program approval is required.

Connect TECH 2 to TIS terminal and select

”Pro gr am Approve”.

GEN3 0005

Powertrain Control Module Location

1. Coolant Surge Tank

2. Powertrain Co ntrol Module (PCM)

After returning to the vehicle select again the link ing

procedure. Now first BCM and PIM are linked and

afterwards the PCM – PIM linking is performed

automatically.

For additional information regarding TECH 2 and

TECH 2 test modes (including this linking

procedure), refer to TECH 2 DIAGNOSIS FOR

BCM in Section 12J-1 LOW SERIES BCM or

Section 12J-2 HIGH SERIES BCM in the VT

Series II Service Information.

PCM MEMORY FUNCTIONS

The following list contain the two types of memory

wi th in th e PCM.

• RAM

• EEPROM (Flash Memory)

RAM

Random Access Memory (RAM) is the

microprocessor scratch pad. The processor can

write into, or read from this memory as needed.

This memory is volatile and needs a constant

supply of B+ voltage to be retained. If the B+

voltage is lost, the memory is lost.

EEPROM (Flash Memory)

A new Service Programming System (SPS) has

been inco rporated with th is Gen III PCM. This SPS

enables technicians to directly update the data

stored in the Powertrain Control Module (PCM).

The part of the PCM which contains the specific

calibration data for a particular vehicle and engine

combination is commonly refered to as the

EEPROM. EEPROM is an acronym for Electrically

Erasable Programmable Read Only Memory. In

eff ect, the dat a in the mem ory m atches the PCM to

the vehicle to provide optimum performance,

driveability, and emissions control.

Sometimes EEPROM data is updated to modify

engine operations. For example, the EEPROM

calibration data may be changed to adjust ignition

timing in order to eliminate a potential detonation

condition or improve idle quality. Before the SPS

was implemented, the procedure for updating

EEPROM data was to simply replace the PCM

EEPROM unit.

The relative ease of changing engine data has led

to inc reased use of af term ark et EPROMs des igned

to enhance performance. Unfortunately, such HOT

EEPROMs often cause engine emissions to

exceed regulated standards. In such instances,

installation of an aftermarket EEPROM is

considered tampering. Governing bodies ruled that

emission-related control modules must be tamper

resistant. These tamper-resistant EEPROMs are

soldered in place as an integral part of the PCM.

Updating the EEPROM data is accomplished

through flash programming.

Flash programming refers to the SPS used to

transfer (or download) PCM data from a computer

terminal and compact disk-read only memory (CD-

ROM) to the vehicle’s PCM. The system is

design ed so that the veh icle verificatio n p roc ed ure s

are required to eliminate EEPROM tampering that

could inc r ease engine emission levels.

There are three main flash programming

techniques listed below:

1. Direct Programming

This is where the vehicle’s Data Link Connector

(DLC) is connected directly to a computer

terminal. On screen directions are then

followed for downloading.

2. Remote Programming

Reprogramming information is downloaded

fr om a computer t er minal to a Tec h 2 scan tool.

The Tech 2 scan tool is then connected to the

vehicle’s Data Link Connector (DLC). On

screen directions are then followed for

downloading.

3. Off-Board Programming

The off-board programming method is used

when a reprogrammable PCM must be

programmed separate from the vehicle. For

example, an independent repair facility may

find it necessary to replace a faulty PCM. On

flash programming equipped vehicles, the

replacement PCM must be programmed with

data for the specific Vehicle Identification

Number (VIN) or the vehicle may not operate

properly.

1.2 POWERTRAIN INTERFACE MODULE (PIM)

The Powertrain Interface Module (PIM), is located

at the left ’A’ pillar behind the kick panel. The PIM

acts as a communication translator between the

PCM and other onboard controllers that use a

different serial data protocol. The GEN III PCM

uses the new Class II serial data to communicate,

while other controllers on the vehicle are designed

to transmit serial data via the conventional

Universal Asynchronous Receive Transm it (UART)

protocol. Since these two types of serial data are

not compatible, a translator or PIM is required to

transmit data in either direction between the PCM

and other controllers. The PIM will interpret the

serial data inform ation and translate UART to Class

II or Class II to UART to support the appropriate

vehicle controller operation. The PIM is the serial

data communication translator for vehicle

operations. It interprets and supplies the following

information in the proper direction for operation of:

• A/C Request.

• Che c k P owe rtrain L amp (CPL).

• Starter Motor Control.

• Theft Deterrent (Starter Motor Cont rol).

• Oil Warning Lamp.

• Power/Ec onom y Lamp.

• Low Co olant La mp.

• Gear Indica to r Lamps.

• Cooling Fan Relay (Low Speed).

A PIM malfunction may affect vehic le operation and

may interrupt starter motor operation. For PIM

diagnosis refer to Section 6C3-2A –

DIAGNOSTICS TABLES – GEN III V8 Engine of

this Ser v ice Inf ormation CD for PIM DTC diagnosis.

There are four (4) PIM DTCs that will set. Each of

thes e DTCs have corr esponding diagnostic tables.

The f our (4) DTCs that will set are:

• DTC B2002: Low Speed Fan No BCM

Response

• DTC B2006: No Serial Data From PCM

• DTC B2007: Starter Relay Voltage High

• DTC B2009: EEPROM Checksum Error

GEN3 0007

Powertrain Interface Module (PIM) Location

GEN3 0006

Powertrain Interface Module (PIM)

1. Throttl e Re laxer Control Mod ule

2. Power train Interface Module

3. Left ‘A’ pillar

There are twenty other PIM DTCs that may set

along with a PCM DTC. If any of the following PIM

DTC s ar e s et, dia gnose the on e or more PCM DTC

first, then clear all PCM and PIM DTC and retest:

• DTC B2017: No Throttle Position Sensor

(TPS) Information

• DTC B2018: No A/C Clutch Information

• DTC B2019: No Engine Speed Information

• DTC B2020: No Vehicle Speed Information

• DTC B2021: N o Commanded Gear

Information

• DTC B2022: No Transmission Type

• DTC B2023: No Low Speed Fan Run On

Information

• DTC B2024: No Low Speed Fan Request

Information

• DTC B2025: No Engin e Coolant Temp

(ECT) Information

• DTC B2026: No Fuel Flow Rate Information

• DTC B2027: No Fuel Used Counter

Information

• DTC B2028: No A/C Pressure Information

• DTC B2029: No PRNDL Inf or ma tion

• DTC B2030: No Engine Oil Information

• DTC B2031: No O il Pressure Information

• DTC B2032: N o Shift Information

• DTC B2033: No Check Powertrain Lamp

(CPL) Information

• DTC B2034: No Low Coolant Level

Information

• DTC B2035: No Barometric Pressure

Information

• DTC B2036: No PCM Informat ion

Thes e additio nal PIM DT C s m ay set if a f ault exis t s

with a r elated s ensor or with the Class II serial dat a

circu it. In either c ase, the PCM will also identify this

fault and set a PCM DTC. All information for these

PIM DT Cs is supplied fr om the PCM to the PIM on

the Class II serial data circuit. If there is a problem

with the Class II serial data circuit, the PIM will not

receive this information and set a DTC B2006 and

or one or more of the ot her twenty PIM DTCs.

The Powertrain OBD System Check will identify a

problem with the ser ial data c irc uit or other circuits,

and direct the technician in the proper direction for

diagnosis. There are no PIM DTC tables

asso ciated with thes e twenty PIM DTCs, so always

diagnos e the PCM fir st.

1.3 ENGINE INFORMATION SENSORS AND SIGNALS

ENGINE COOLANT T EMPERATURE (ECT) SENSOR

The Engine Coolant Temperature (ECT) sensor is

a ther mis tor (a r esistor which changes value base d

on temperature) mounted in the left cylinder head.

Low coolant temperature produces a high

resistance (100,000 ohms at -38°C) while high

temperature causes low resistance (70 ohms at

130°C).

The PCM supplies a 5.0 volt signal to the engine

coolant temperature sensor through a resistor in

the PCM and measures the voltage. The voltage

will be high when the engine is cold. The voltage

will be low when the engine is hot. The PCM

calculates the engine coolant temperature by

measuring the voltage. The engine coolant

temperature affects most systems the PCM

controls.

The Tech 2 scan tool displays engine coolant

temperature in degrees. When the engine starts

the engin e cool ant tem peratur e should rise s teadily

to about 90°C then stabilise when thermostat

opens. The engine coolant temperature and intake

air t em peratur e s hould be clos e to e ach other if the

engine has not been run for several hours

(overnigh t). T he following D TCs set when t he PCM

detects a malfunction in the engine coolant

temperature sensor circuit:

• DTC P0117: ECT Sensor Circuit Low

Voltage.

• DTC P0118: ECT Sensor Circuit High

Voltage.

• DTC P0125: ECT Excessive Time to Closed

Loop Fuel Control.

• DTC P1114: ECT Sensor CKT Intermittent

Low Voltage.

• DTC P1115: ECT Sensor CKT Intermittent

High Voltage.

GEN3 0008

Engine Coolant Temperature (ECT) Sensor

1. ECT Electrical Connector

2. Connector Tab

3. Engine Coolant Tem perature (ECT ) Sensor

Section 6C3-4 SPECIFICATIONS – GEN III V8

Engine of this Service Information CDcontains a

table to chec k for sensor resistanc e values rela tive

to temperature.

T6B3047

Engine Coolant Temperature (ECT) Sensor

Location

1. ECT Sensor

2. Left Cylinder Head

ENGINE COOLANT LEVEL SWITCH

The engine coolant level switch is used to inform

the PCM when the coolant level is at a calibrated

low level.

When the engine coolant is at normal operating

level, the engine coolant level switch float inside the

surge tank will rise and close the sensor contacts

pulling the PCM supplies buffered B+ low.

When the coolant level is low, the engine coolant

level switch will remove the earth signal, causing

the PCM o utput B+ signal to go high. T he PCM will

then send a serial data message to the instrument

panel cluster instructing the instrument panel

cluster to turn ON the Lo w Co o l an t Warning La mp.

For diagnosis of the engine coolant level switch,

refer to Section 6C3-2C FUNCTIONAL CHECKS

– GEN III V8 Engine in this Section.

The engine coolant level switch is located in the

coolant surge tank . T he engine coolan t level switch

is serviceable only by replacing the surge tank.

Refer to Section 6B3 ENGINE COOLING of the

VT Series II Service Information, for surge tank

replacement.

GEN3 0153

Engine Coolant Level Switch Location

1. Engine Coolant Level Switc h Ele c trical Connector

2. Power train Control Mod ule (PCM)

MASS AIR FLOW (MAF) SENSOR

The Mass Air Flow (MAF) sensor measures the

amount of air which passes through it. The PCM

uses this information to determine the operating

condition of the engine in order to control the fuel

delivery. A large quantity of air indicates

acceleration. A small quantity of air indicates

decele ration or idle.

The Tech 2 scan tool reads the MAF value and

displays it in grams per second (g/s). The MAF

sensor displays between 6 g/s and 9 g/s at idle on

a fully warmed up engine. The MAF sensor values

should change quickly on acceleration, but the MAF

sens or values sho uld re m a in relat ively st able at any

given RPM. When the PCM detects a malfunction

with the MAF senso r, the PCM will switch to Speed

Density for fuel control.

The following DT Cs are se t when the PCM detec ts

a m alfunction in the MAF sens or circu it:

• DTC P0101: Mass Air Flow System

Performance.

• DTC P0102: MAF Sensor Circu it Low

Frequency.

• DTC P0103: MAF Sensor Circuit High

Frequency.

Mas s Air Fl ow (MAF) Se nsor

Three sensing elements are used in this system.

One senses the amb i ent air tem perature. T he other

two sensing elem ents are heat sensing elem ents.

The ambient air temperature sensor is mounted in

the lower half of the sens or housing.

The two heater sensing elements are heated to a

calculated temperature that is significantly above

the ambient air temperature. The two heater

sensing elements are connected electrically in

parallel and mounted directly in the air f low stream

of the sensor hous ing. One se nsor is in the top and

the other sensor is in the bottom of the sensor

housing. This is done so that the air meter is less

sensitive to upstream ducting configurations that

could skew the flow of air through the housing.

As the air passes over the heater sensing

elements, the elements begin to cool. By

measuring the amount of voltage required to

maintain the heater sensing elements at the

calculated temperature above ambient, the

incoming air flow rate can be calculated.

After the Mass Air Flow sensor has developed a

signal related to the mass air flow rate, the MAF

sensor then sends the signal to the PCM. In order

to pr eserve the a ccuracy of the voltage s ignal from

the mass air flow sensor, the voltage is converted

to a frequency signal then sent to the PCM.

GEN3 0010

Sensing E l em e nts

1. Heater Sensing Elements

2. Ambient Temperature Sensor

T26C3002

MAF Sensor Location1. Air Cleane r Housing

2. Mass Air Flow (MAF) Senso r

INTAKE AI R TEMPERATURE (I AT) SENSOR

The Intake Air Temperature (IAT) sensor is a

thermistor which changes value based on the

temperature of air entering the engine. Low

temperature produces a high resistance (100,000

ohms at -38°C/-39°F). A high temperature causes

low resistance (70 ohms at 130°C/266°F). The

PCM supplies a 5.0 volt signal to the sensor

through a resistor in the PCM and measures the

voltage. T h e voltage will b e high when the inc om ing

air is cold, and low when the air is hot. The PCM

calculates the incoming air temperature by

m easuring the IAT voltage. T he IAT sensor signal is

used to adjust spark timing according to incoming

air density.

The Tech 2 scan tool displays temperature of the

air entering the engine, which should read close to

ambient air temperature when engine is cold. The

temperature should rise as underhood temperature

increases. If the engine has not been run for

several hours (overnight) the IAT sensor

temperature and engine coolant temperature sho uld

read close to each other. The following DTCs are

set if the PCM detects a malfunction in the IAT

sens or circuit:

• DTC P0112: IAT Sensor Circuit Low Voltage.

• DTC P0113: IAT Sensor Circuit High Voltage.

• DTC P1111: IAT Sens or C KT I nter m it te nt Hi gh

Voltage.

• DTC P1112: IAT Sensor CKT Intermittent Low

Voltage.

Intake Air Temperature (IAT) Sensor

T26C3004

IAT Sensor Loc ation

1. Air Cle aner Housin g

2. Intake Air Temperature (IAT) Sensor

3. A/C Re frigerant Pres sure Tr ansducer

MANIFOLD ABSOLUTE PRESSURE (M AP) SENSOR

The Manifold Absolute Pressure (MAP) sensor

responds to changes in the intake manifold

pressure. The pressure changes as a result of

engine load and speed. The map sensor converts

this to a voltage output.

A closed throttle on engine coast down produces a

relatively low MAP output voltage. A wide open

throttle produces a high MAP output voltage. This

high output voltage is produced because the

pressure inside the m anifold is the same as outside

the manifold. The MAP is inversely proportional to

what is measured on a vacuum gauge. The MAP

sens or is used for the following:

• Altitude determ i nation.

• Ignition timing control.

• Speed density fuel management default.

Manifold Absolute Pressure (MAP) Sensor Location

1. Manifold Abso lute Pressure (MAP) Sensor

2. Camshaft Position (CMP) Sensor

3. Oil Pressure Sensor

4. Connector to Knock Sensor Jumper Harness

SPEED DENSITY SYSTEM

Three specific data sensors provide the PCM with

the basic information for the fuel management

portion of its operation. That is three specific

signals to the PCM esta blish the en gine speed and

air density factor s. Th e engine s peed signal come s

from the ignition system. The PCM uses this

information to determine engine speed (RPM). Air

density is der ived from IAT and MAP sensor input s.

The IAT sensor measures the air temperature that

is entering the engine. The IAT signal works in

conjunction with the MAP sensor to determine air

density. As the intake manifold also increases and

additional f u el is req uire d. This inf o rmation from the

IAT and MAP sensors is used by the PCM to

control injector pulse width.

The Speed Density system is only needed when

there is a Mas s Air Flow ( MAF) s ens or m alf un ction.

If the PCM detects a malfunction with the MAF

sens or circuit, the PC M will default to speed density

fuel management.

When the PCM detects a malfunction in the MAP

sensor circuit, DTC P0107: MAP Sensor Circuit

Low Voltage or DTC P0108: MAP Sensor Circuit

High Volta ge will set.

Manifold Absolute Pressure (MAP) Sensor Location1.

Manifo ld Absolute Pressure (MAP) Sensor

2. MAP Sensor Harness Connector

HEAT ED OXYGEN SENSORS (HO2S)

The Heated Oxygen Sensors are mounted in the

exhau st syst em where t hey can mo nitor he oxygen

content of the exhaust gas stream. The oxygen

present in t he exhaust gas reac ts with the s ensor to

produce a voltage ou tput.

This voltage should constantly fluctuate from

approximately 100mV (high oxygen content - lean

mixture) to 900 mV (low oxygen content - rich

m ixtur e) . T he hea te d oxygen senso r vo ltage ca n be

monitored with a scan tool. The PCM calculates

what fuel mixture command to give to the injectors

(lean mixture - low HO2S voltage = rich com mand,

rich m ix ture - high HO2S volt age = lean com mand )

by monitoring the voltage output of the oxygen

sensors.

These oxygen sensors ar e mounted in the exhaust

pipes and are referred to as Bank 1 Sensor 1 (left

exhaust pipe) Bank 2 Sensor 1 (right exhaust pipe).

The PCM sets the following DTCs when the PCM

detec ts an HO2S signal circuit that is low:

• DTC P0131: Bank 1 Sensor 1 HO2S.

• DTC P0151: Bank 2 Sensor 1 HO2S.

The PCM sets the following DTCs when the PCM

detec ts an HO2S signal circuit that is high:

• DTC P0132: Bank 1 Sensor 1 HO2S.

• DTC P0152: Bank 2 Sensor 1 HO2S.

The PCM sets the following DTCs when the PCM

detects no HO2S activity:

• DTC P0134: Bank 1 Sensor 1 HO2S.

• DTC P0154: Bank 2 Sensor 1 HO2S.

A fault in the heat ed oxygen se nsor heater elem ent

or its ignition feed o r earth results in an increa se in

time to Closed Loop fuel control. This may cause

increased emissions, especially at start-up. The

following DTCs are set when the PCM detects a

malfunction in the HO2S heater circui ts:

• DTC P0135: Bank 1 Sensor 1 HO2S heater.

• DTC P0155: Bank 2 Sensor 1 HO2S heater.

RESPONSE TIME

The PCM also has the ability to detect HO2S

response, switching, transition time, and incorrect

ratio voltage problems. The PCM stor es a DTC that

indicates degraded HO2S performance if a HO2S

response switching , transition time , or ratio pr oblem

is detected.

OXYGEN SENSOR CONT AMINANTS

Carbon

Carbon or soot deposits result from an extremely

rich air-fuel mixture. Carbon does not harm an O2

sensor. Deposits can be burned off in the vehicle

by running the engine at least part throttle for two

minutes.

GEN3 0013

Heated Oxyg en Sensor (HO2S) Cut away

1. Four Wire In-Line Connector

2. Heater Termination

3. Water Shield Assembly

4. Sensor Lead

5. Flat Seat Shell

6. Seat Gasket

7. Out er Electrode an d Pr otective Co ating

8. Rod Heater

9. Inner Electrode

10. Zirconia Element

11. Insulator

12. Clip Ring

13. Gripper

Silica

Certain RTV silicone gasket materials give off

vapours that may contaminate the oxygen sensor.

The sand like particles from the RTV silica embed

them selves in t he oxygen se nsor elem ent and plug

the sur face. T his will result in a lazy oxygen sensor

respo nse tim e. T he sens or will also have a whitis h

appearance.

Silica co ntam ination c an also be ca used by silicone

in the f ue l. Car eless f ue l handling pr a ctice s with th e

transport containers can result in unacceptable

concentrations of silicone in the fuel at the fuel

pump.

There is also a possibility of silica contamination

caused when installing vacuum hoses or fittings.

Do not use silicone sealers on the gaskets or the

exhaust joints.

Lead

Lead glazing of the oxygen sensor can occ ur when

leaded fuel is burned.

Other Substances

Oil deposits will ultimately prevent oxygen sensor

operation. The O2 sensor will have a dark brown

appearance. Causes of high oil consumption

should be c hec k e d. The a dditives in ethylene glycol

can also affect the oxygen sensor performance.

This produces a whitish appearance. If antifreeze

enter s the exhaus t s ys tem , you will likely encounter

other, more obvious, symptoms of cooling system

trouble.

Multiple Faul ts

If you encounter multiple or repeat oxygen sensor

faults on the s ame vehicle, consider contamination.

Leaded fuel, silica contamination from uncured,

low-grade (non approved) RTV sealant, and high oil

cons umpt ion are possible.

A problem in the either oxygen sensor circuits or

fuel system should set a DTC( s).

THROTTL E POSITION (TP) SENSOR

The Throttle Position (TP) sensor is a

potentiometer. The TP sensor is connected to the

throttle shaft on the throttle body. The PCM

calculates throttle position by monitoring the

voltage on the signal line. The TP sensor signal

changes as the throttle valve angle is changed

(accelerator pedal moved). The TP sensor signal

voltage is low at a closed throttle position. The TP

sens or signal voltage inc r eases as the throttle valve

opens so that at Wide Open Throttle (WOT), the

output voltage should be above 4.0 volts.

The PCM 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. This may cause an unstable idle

becau se the PCM detect s the thrott le is moving.

The following DT Cs are se t when the PCM detec ts

a malfunction with the TP sensor circuits:

• DTC P0121: TP Sensor Circuit Insufficient

Activity.

• DTC P0122: TP Sensor Circuit Low Voltage.

• DTC P0123: TP Sensor Circuit High Voltage.

• DTC P1121: TP Sensor CKT Intermittent

High Voltage.

• DT C P112 2: T P Sens or CKT Inte rmitt ent Low

Voltage.

Throttle Position (TP) Sensor1. TP Sensor

2. Throttle Body

3. IAC Valve

GEN3 0015

TP Sensor - Typ i cal

1. TP Sensor

2. Throttle Plate

3. Power train Control Mod ule (PCM)

KNOCK SENSORS (KS)

A Knock Sensor (KS) system is used in order to

control engine spark knock. The KS system is

designed to retard spark t i ming up to 20° in order to

reduce spark knock in the engine. This allows the

engine to use m axim um spark ad vance to improve

driveability and fuel economy.

The knock sensor system is used to detect engine

detonation. The knock sensors produce an AC

voltage which is s ent t o the PCM. The PC M r etard s

the spark timing based on signals from the KS

sensors. The amount of AC voltage produced by

the sensors is determined by the amount of knock.

This AC signal voltage t o the PCM is proc essed by

a Signal Noise Enhancement Filter (SNEF) module.

The SNEF module is used to determine if the AC

signal coming in is noise or detonation. This SNEF

m odule is part o f the PC M and ca nnot be re placed.

The PCM then adjusts t he ignition tim ing to reduce

the spark advance. How much the timing is

retarded is based upon the amount of time knock

that is detected and is limited to a maximum value

of 20° degrees. After the detonation stops, the

timing will gradually return to its calibrated value of

spark advance.

Knock (KS) Sensor

The Knock Sensor system will only retard timing

after the f ollowing conditions are met:

• The engine run time is greater than 20

seconds.

• The engine speed is greater than 16 50 RPM.

• The engine coolant temperature is greater

than 70°C (158°F).

• The MAP is less than 60 kPa.

The Tech 2 scan tool has several positions for

diagnos ing the KS circuit:

• Knock Retard indicates the amount of spark

the PCM is removing from the IC spark

advance in response to the signal from the

Knock Sensors.

• Spark indicates the amount of spark advance

being commanded by the PCM on the IC

circuit.

DTC P0325 indicates an internal PCM malfunction

related to the KS system. DTCs P0327 and P0332

indicate that a Knock Sensor or Knock Sensor

circuit is malfunctioning. If these DTCs are set,

ref er to applicable DTC table.

Knock Sensor Location

1. Fr ont Knock Sensor

2. Rear Knock Se nsor

3. Left Cylinder Head

PARK, REVERSE, NEUTRAL, DRIVE, LOW (PRNDL) SWITCH

The transmission PRNDL module is a multi-signal

switch which sends a signal to the PCM to indicate

gear selection. The PCM will then determine the

signal from the PRNDL module and send a

command via serial data communication to the

instrument panel clust er to turn ON the correct gear

indicator lamp for the gear that is be ing selected.

The PRNDL module uses four discrete circuits to

pull four PCM voltag es low in various co mbinations

to indicate each gear range. The voltage level of

the circuits is represented as CLOSED = earthed,

and OPEN = open cir c uit. Th e fou r st ates displa yed

represents decoder P, A, B, and C inputs.

The Tech 2 scan tool will display all four circuits

(P, A, B, C ) and the ap pro pria te open and clos ed to

represent the gear selected. If the gear selected

does not match the OPEN/ CLOSED state as

displayed in the table on the scan tool, or the

instrument panel cluster gear lamp (if fitted) does

not light up for the gear selected, there is a fault in

the PR NDL select c irc uit or in the Instru m ent Panel

(IP) cluster.

The PRNDL operation indicates to the PCM what

gear the shift selec tor is in. Th is inf ormatio n is used

for the IAC valve operat i on.

Important: Idle quality will be af fect ed if the vehicle

is driven with the PRNDL switch disconnected.

Having the switch disconnected may also cause a

VSS DTC to set.

For additional details of the PRNDL switch location

and adjustment, refer to Se ct ion 7C 4 AUTOMA TIC

TRANSMISSION, On-Vehicle Servicing of the VT

Series II Service Information.

A/C REQUEST SIGNAL

When received, this signal tells the PCM that the

driver want s t he air condit ioning to operat e. On non

ECC equipped vehicles the signal originates at the

instrument panel A/C s witch, but must pass thr ough

the BCM, which sends a serial communications

message to the PIM, which in turn passes the

switch state on to the PCM.

If the vehicle is equipped with Electronic Climate

Control, this A/ C re quest signa l comes dir ec tly from

the ECC module via a serial message to the PIM

which then passes the request to the PCM. The

PCM uses th is signal to - adjust the Idle Air Control

(IAC) po sition to com pe nsat e for the additional load

placed on the engine by the air conditioning

compressor, and then - energises the A/C control

relay, to operate the A/C compressor.

TRANSMISSION RANGE / PRNDL SWITCH VALID

INPUT COMBINATIONS

GEAR

POSITION

SELECTED

SCAN TOOL PRNDL DISP L A Y

(P, A, B, C)

P A B C

PARK (P) CLOSED CLOSED OPEN OPEN

REVERSE (R) OPEN CLOSED CLOSED OPEN

NEUT RA L (N) CLOSED OPEN CLOSED OPEN

DRIVE 4 (D) OPEN OPEN CLOSED C LOSED

DRIVE (3) CLOSED CLOSED CLOSED CLOSED

DRIVE 2 (2) OPEN CLOSED OPEN CLOSED

DRIVE 1 (1) CLOSED OPEN OPEN CLOSED

A/C REFRIGERANT PRESSURE TRANSDUCER

This signal is used by the PCM in order to enable

the cooling fans when the A/C compressor head

pressure reaches a predetermined value. DTC

P0530 sets if a fault is present in the A/C

refrigerant pressure sensor circuit.

The PCM disables the A/C compres s or clutc h when

the PCM sets an A/C system DT C. Refer to the A/C

Refrigerant Pressure Transducer Circuit Diagnosis

in Section 6C3-2C FUNCTIONAL CHECKS –

GEN III V8 Engine of this Service Inform ation CD, if

the A/C Refrigerant Pressure Transducer is faulty.

T26C3004

A/C Refrigerant Pressure Transducer Location

1. A/C Re friger ant Pressure Transducer

VEHICLE SPEED SENSOR (VSS)

The Vehicle Speed Sensor (VSS) is a pulse

counter type input that informs the PCM how fast

the vehicle is traveling. The VSS system uses an

inductive sensor mounted in the tail housing of the

transmission and a toothed reluctor wheel on the

tailshaft. The teeth of the reluctor wheel alternately

interfere with the magnetic field of the sensor

creating an induced voltage pulse as the reluctor

rotates. Each brake in the field sends a pulse to the

PCM.

For automatic transmission equipped vehicles 40

pulses per tailshaft revolution are generated. This

results in 100196 pulses per mile (62260 PPK)

input to the PCM.

For manual transmission equipped vehicles 17

pulses per tailshaft revolution is generated. This

results in 47992 pulses pe r mile (29820 PPK) input

to the PCM.

For both transmissions the output is 10020 pulses

per m ile (6226 PPK). A f ault with th e spe ed sensor

will cause DTC P0608 to set.

The PCM uses the signal from the vehicle speed

sens or to determine the following:

• The vehicle spe ed.

• The control sh ift points .

• Calc ulate transmission slip.

• The engine fueling modes.

• Chime Module.

IMPORTANT: The automatic transmission VSS

resistance should be 1470-2220 ohms when

measured at 20°C (68°F). Output voltage of the

VSS varies with s peed fr om a minim um of 0.5 volts

AC at 10 0 RPM to m ore than 100 volt s AC at 8000

RPM.

GEN3 0019

Vehicle Speed Sensor (VSS)

1. Automatic Transmission Tail Housing

2. Vehicle Speed Sensor (VSS) Reta ining Bolt

3. Vehicle Speed Sensor (VSS)

A Diagnostic Trouble Code will set if a fault exists

in the Vehicle Speed Sensor circuit.

For automatic transmission: as the vehicle is

acce lerated, the PCM will shift the transm ission into

second gear at approximately 50 km/h. If the

vehicle speed signal is not present while in second

gear, a DTC will set .

The PCM will substitute a default value for the

vehicle speed if the fault occurred in fourth gear. If

the f ault occurred in park , neutral, or f irst gear, the

PCM will allow 1-2 shifts to occur. If a DTC is set,

then the PCM will default into third gear. If the

conditions for a DTC no longer exist, then normal

operation will r esume after the next ignition cycle.

For manual transmission: as the vehicle is

accelerated in any forward gear from a closed

throttle, and no vehicle speed is indicated to the

PCM, a DTC will set.

GEN3 0020

Vehicle Speed Sensor To Reluctor Wheel

1. Reluctor Wheel (Rotor)

2. O-Ring

3. Electrical Connector

4. Magnetic Pickup

CRANKSHAFT POSITION (CKP) SENSOR

The Crank sh af t Position (CKP) senso r provides the

PCM with crankshaft speed and crankshaft

position.

The PCM monitors the CKP sensor signal circuit

for m alfun ctions. The PCM sets a DTC P0335 or a

DTC P0336 when the CKP sensor is out of the

normal operating range.

Crankshaft Position Sensor (CKP) Location

1. Starter Mounting Pad on Engine Block

2. CKP Sensor

3. CKP Mounting Bolt

CA MSHAFT POSITION (CMP) SENSOR

The Camshaft Position (CMP) sensor is mounted

through the top of the engine b lock at the rear of the

valley cover and works in conjunction with a 1X

reluctor wheel on the camshaft. The reluctor wheel

is inside t he engine, imme diately in fron t of the rear

cam bearing. The PCM provides a 12 volt power

supply to the CMP sensor as well as a earth and a

signal circ uit.

The PCM uses the camshaft position sensor in

order to determine whether a cylinder is on a firing

or exhaust stroke. The reluctor wheel interrupts a

magnetic field produced by a magnet within the

CMP sensor as the camshaft rotates. The CMP

sensor’s internal circuitry detects this and produces

a signal which the PCM reads. The PCM uses this

1X signal in combination with the Crankshaft

Position s ens or 24 X s ignal in or der to det er mine the

Crankshaft Position and stroke. This diagnostic for

the Camshaft Position sensor checks for Camshaft

Position sensor signal. The PCM also monitors the

CMP sensor signal circuit for malfunctions. The

following DTCs set when the PCM detects a CMP

sens or that is out of the normal operating r ange:

• DTC P0341: Camshaft Position ( CMP)

Sens o r Cir cu i t P e rfor mance .

• DTC P0342: Camshaft Position ( CMP)

Sensor Circuit Low Voltage.

• DTC P0343: Camshaft Position ( CMP)

Sensor Circuit High Voltage.

GEN3 0022

Camshaft Posi tion Senso r (CMP) Location

1. CMP Mounting Bolt

2. CMP Sensor

3. Top Rear of Engine Block

BATTERY VOLTAGE

The PCM continually monitors battery voltage.

When the battery voltage is low, the ignition system

may deliver a weak spark and the injector

mechanical movement takes longer to open the

injector.

The Powert rain Control Module will compensate by:

1. Increasing the ignition coil dwell time if the

batte r y voltage is les s than 12 volts.

2. Increasing the engine idle RPM if battery

voltage drops below 10 volts.

3. Increasing the injector pulse width if the

battery voltage drops below 10 volts.

On vehicles equipped with automatic transmission,

Diagnostic Trouble Code (DTC) P0563 will set

when the ignition is ON and PCM voltage is more

than 17 volts for about 5 seconds.

Diagnostic Trouble Code (DTC) P0562 will set

when the ignition is ON and PCM voltage is less

than 5 volts f or about 5 s econds.

TRANSMISSION ECONOMY/POWER SWITCH

The Economy/Power switch is used to modify

upshifts and shift t imes. The driver can select either

Economy or Power mode with the switch (1)

located on the centre console. A third mode,

Cruise, is available via a switch located on the

indicat or stalk (where fitt ed).

Two green indicator lamps of 1.2 watts at 12 volts

are located in the instrument cluster and display

POW E R or CRUISE when illumina ted to inform the

driver of the mode that is en abled.

The PCM provides a voltage signal of about 12

volts, and monitors the status of this circuit. In the

Econom y position, the switch is open and the PCM

voltage status signal remains high, about 12 volts.

The PCM does not allow shift point changes in the

Economy mode. When the transmission switch is

pressed to the Power position the switch is

momentarily closed and the PCM voltage status

signal is mom entarily pulled low, to about 0.5 volts.

The PCM senses this voltage momentary voltage

drop and enables Power mode (alternate shift

pattern tab les to be utilised).

GEN3 0154

Transmission Econ omy/Power Switch

1. Automatic Tr ansmission Economy/Power Switch

In the Power mode, the Torque Converter Clutch

(TCC) can be applied in 3rd and 4th gears. When

the TCC is applied in 3rd gear it will stay applied

until the normal 4th gear upshift criteria is met.

When the 3-4 upshift occurs, the TCC will be

released momentarily. Also, in the Power mode

while in D gear select position, the PCM will delay

the 1-2 and 2-3 shift while under light throttle. The

shift patterns will be the sam e in the Economy and

Power m odes if the Th rottle Pos ition (TP) sensor is

between 80% - 100%. The Power mode should be

used when towing, as applying the TCC in 3rd and

4th gear reduces slippage in the TCC and thus

reduces heat build up.

In Cruise mode operation, when the driver ac tivates

the cruise control, the POWER lamp and Power

mode will turn OFF (if vehicle was in power mode)

and a CRUISE lamp will illuminate on the

instr ument panel. T he tr ansmis sio n shif t patter n will

switch to cruise shift pattern. W hen in cruise mode

the PCM will m odify the trans miss ion calibration so

that transmission shift activity is reduced.

W hen the key is turned ON, the PCM shift mode is

set to the last mode that was previously selected

(Economy/Power). The cruise control is set to OFF

at every key ON cycle.

For replacement of the Economy/Power switch,

refer to Section 7C4 AUTOMATIC

TRANSMISSION On Vehicle Service of the VT

Series I Service In formation.

THEFT DETERRENT SYSTEM

The thef t deter rent system on VT Series Models uses a remote coded key to arm and disar m the system , as well as

electrically lock or unlock all doors and tailgate (station wagon), or operate the boot unlock mechanism (sedan

models).

The th eft deter rent alert indicat or LED is used to indicate the state of the system . A flashing LED indicates that the

system is ar m ed and cons equen tly the vehicle cannot be s tart ed. When the LED is turned off , the BCM is disarm ed

and the engine can be started. The theft deterrent LED is incorporated into the trip computer module in the

instrument panel fa cia.

W hen the GEN III V8 ignition switch is turned to the ON position, the BCM polls the PIM and sends an encrypted

BCM/Key security code (The security code is received via the BCM slip ring or remote receiver in the event of no

slip ring communication). The PIM compares the received security code with its stored security code and if the

codes match, the PIM will continue engine cranking and send a separate encrypted security code on the Class II

serial data circuit to the PCM. The PCM compares this code with its stored security code and if the codes match,

the PC M will enable injection of fue l to continue. The PIM will return an O K TO ST ART messag e on the UART serial

data c ir cuit, which t ells the BCM to jump from SHORT LOOP mode to the LONG LOOP mode.

NOTE 1: Regardless of the engine configuration, it is very important that the remote coded key reader is aligned

correctly with the ignition lock assembly. Misalignment with the remote coded key contact may occur resulting in

intermitt ent or no engine c r anking or starting.

NOTE 2: Should the engine crank briefly when the ignition switch is turned to the START position (ie. due to

m isaligned or a fault y remo te code d key reader) then pr essing t he unlock butto n on the r emot e coded k ey will also

disarm the theft deterrent system.

Refer to Section 12J-1 LOW SERIES BODY CONTROL MODULE or 12J-2 HIGH SERIES BODY CONTROL

MODULE in the VT Series II Service Inform ation for further information and diagnosis.

GEN 3 0024

11 97

Theft Deterrent Sy stem

1. Remote Coded Key

2. Remote Receiver Module

3. R emote Coded K ey Reader Asse m bly

4. Signal from Remote Receiver Modul e t o BCM

5. Signal from Key Reader to BCM

6. Body Control Module (BCM)

7. Starter Relay

8. Starter Motor

9. Signal from PIM to Start Relay

10. Powertrain Interface Module (PIM)

11. Signal from BCM to PIM for Starter

12. Theft Deterrent Alert Indicator LED Control

13. OK to Start from BCM

14. Is It OK To Start Request from PCM

15. Signal from PCM for Injector Control

16. Fuel Injectors (8)

17. Powertrain Control Module (PCM)

OIL PRESSURE SENSOR

The engine oil pressure sensor is a resistor which

changes value based on pressure and is mounted

to the rear left top of the engine.

The PCM su pplie s a 5 volt signal to the oil pres sur e

sensor through a resistor in the PCM and

measures the voltage on the signal circuit. By

measuring the voltage, the PCM calculates the

engine oil pressure and determines when to turn

ON the low oil warning lamp .

If t he low oil warning lamp st ays ON all the tim e, or

does not illuminate, more than likely there is a

problem with the instrument panel cluster or the

bulb. Using the Tech 2 scan tool to control the low

oil warning lamp will determine its operation.

When the PCM detects a malfunction in the oil

pressure sensor circuit, the following DTCs will set:

• DTC P0522: Engine Oil Pressure Circ uit

Low Voltage

• DTC P0523: Engine Oil Pressure Circ uit

High Voltage

Oil Pressure Sensor

1. Manifold Abso lute Pressure (MAP) Sensor

2. Camshaft Position (CMP) Sensor

3. Oil Pressure Sensor

4. Connector to Knock Sensor Jumper Harness

MANUAL TRANSMISSION REVERSE LOCKOUT SOLENOID

When the key is ON the PCM supplies an earth

signal to the reverse lockout solenoid, allowing

shifting into reverse. When the reverse lockout

solenoid is energised, the driver can shift the

transmission into reverse. The PCM enables the

reverse lockout solenoid whenever the vehicle

speed is below 3 km/h. When the vehicle speed is

above 5 km/h, the PCM will de-energise the

solenoid, which pr events t he driver from shifting the

transm ission into reverse.

GEN3 0147

Reverse Lockout Sol enoid

1. Reverse Lockout Solenoid

2. Reverse Lockout Harness Conn ector

BRA KE PEDAL SWITCHES

There are two electrical switches mounted on the

brake pedal support br acket.

Stop Lamp Switch

The stop lamp switch (4) is a normally open switch

that supplies B+ from fuse F5 to the rear brake

lamps when the brake pedal is depressed. It also

supplies 12 volts to the cruise control actuator and

a brake applied 12 volt input signal to terminal 14 of

the ABS or ABS/ETC control mod ule.

If the ABS or ABS/ETC control module does not

receive this sign al at star t up, t he ABS or ABS/ETC

self test will begin when vehicle speed is

approx imately 6k m/h. Should th e bra k es b e applied

before this initial ABS or ABS/ETC cycle, the self

test will not occur until the vehicle speed is

approximatel y 18 km/h.

Should the brake switch signal be received at any

time during Traction Control mode, the ABS/ETC

control module will inhibit Traction Control and

allow for manual braking. Engine torque

m anagem ent m ay still occ ur if necessary.

This stop lamp switch 12 volt signal is also used to

signal the cr uise c ontrol m odule to disengag e when

the brake pedal is depressed. For all service

operations on the stop lamp switch, refer to

Section 12B LIGHTING SYSTEMS of the VT

Series II Service Information.

Cruise Control Release Switch

The cruise electrical release switch (2) is a

normally closed switch, and supplies a 12 volt

signal from the Low Traction Lamp (through a

resistor adjacent to the Low Traction Lamp) to the

PCM, Cruise Control Actuator, and the ABS or

ABS/ETC module. When the brake pedal is

depressed, the 12 volt supply signal is removed

fr om th e PC M and the Cruise Control Actuator.

When the PCM determines that this 12 volt signal

has been removed, the PCM will disengage the

automatic transmission Torque Converter Clutch

(TCC) until this 12 volt signal is re-established to

the PCM. Also, the cruise control actuator will

deactivate the cruise control operation (the cruise

set speed will be retained in memory). Once the

brake pedal is released, the cruise set speed can

be re-established by selecting the cruise resume

switch.

GEN3 0181

Stop Lamp Switch Location

1. Cruise Electrical Re lease Switch Connector

2. Cruise Elect rical Release Switch

3. Stop Lamp Electrical Connector

4. Stop Lamp Switch

5. Brake Peda l Supp or t B r ac ket

6. Brake Pe da l A rm Asse mbly

Also, associated on this cruise electrical release

switch (2) circuit is the ABS/ETC module Low

Traction Lamp control. The ABS or ABS/ETC

module will supply an earth signal to the Low

Traction Lamp when traction control is being

requested. When the PCM receives this earth

signal the PCM will inhibit TCC operation and

activate the engine torque management operation.

The cruise control will also deact iva te operation.

If there is a problem with the circuit between the

Low Traction Lamp and the PCM, DTC P0719 or

P0724 will set.

Both switches are used to signal the cruise control

m odule s o th at if one sho uld f ail, the sec ond switc h

will still generate a signal to the cruise control

module to disengage the cruise control operation.

For all service operations on the cruise electrical

release switch, Refer to Section 12E CRUISE

CONTROL of the VT Series II Service Information.

1.4 FUEL CONTROL SYSTEM

SYSTEM OVERVIEW

An electric fuel pump, located in the fuel tank with

the fuel sender assembly, pumps fuel through an

in-line f uel f ilter t o the fu el rail a ssem bly. The pum p

provides fuel at a pressure greater than is needed

by the inject or s. The fuel pr es su re re gulator, pa rt of

the fuel sender assembly, keeps fuel available to

the injectors at a regulated pressure. A separate

pipe ret ur ns unused fuel to the fuel tank.

COMPONENTS

Fuel Tank Vent Valve

The f uel ta nk vent valve is loc ated in the r ear of the

vehicle near the fuel tank. The fuel tank vent valve

is a pressure/vacuum relief valve. When the fuel

tank pressure exceeds a specified pressure, the

valve opens allowing the tank pr essur e to bleed off.

When the fuel tank is in a vacuum condition, the

vent valve opens when the vacuum is within a

spec ified rang e allowing fresh air to be pulled in.

Fuel Tank

The fuel tank is constructed from a special plastic

and is located under the rear compartment floor. It

is secured to the vehicle by three metal straps that

attach to the fram e.

Fuel Tank Filler Pipe

The fuel tank filler pipe has a built-in resistor and

deflector in order to prevent refueling with leaded

fuel.

Fuel Filler Ca p

NOTE: If a fuel filler ca p requires replac ement , use

only a fuel filler cap of the s ame type. Failure to use

the correct fuel filler cap can result in a serious

m alfunc tion of the fuel and evaporative systems.

The fuel filler cap incorporates a torque-limiting

device which prevents the cap from being over

tightene d. T o ins tall the cap, t urn the cap clock wise

until you hear three audible clicks. This indicates

that the cap is correctly torqued and fully seated.

Fuel Filler Cap

Fuel Sender Assembly

The fuel sender assembly, mounted inside the fuel

tank, is att ached t o th e top of t he fu el tank . The f uel

sender assembly consists of the following major

components:

• The fuel level sensor

• The fuel pump

• The fuel pressure regulator

• The fuel pump strainer

NOTE: The only serviceable part of the fuel sender

assembly is the fuel lever sensor. All other

components require replacement of the complete

fuel sender assem bly.

Fuel Pump

The fuel pump attaches to the fuel sender

asse m bly inside the f uel ta nk an d is an elec t ric high

pressure gear rotor pump. The fuel pump provides

fuel t o the fuel r ail as sem bly at a sp ecified flow and

pressure. Excess fuel returns to the fuel tank by the

return pipe.

The fuel pump delivers a constant flow of fuel to the

engine even during low fuel conditions and

aggres sive vehicle m anoeuvres. T he PCM controls

the electric fuel pump operation through a fuel

pump relay. The fuel pump flex pipe has a quick-

connect f itting . T he fu el r eturn hose a ttaches to the

fuel pressure regulator. The fuel pump flex pipe

acts to dampen the fuel pulses and noise

generated by the fuel pump.

T26C3007

T8A1001

Fuel Se nder Assembly

1. Primary Umbrella Valve

2. Reservoir

3. Floating J e t Pump (“a” High Fuel / “b” Low Fuel)

4. Internal Filter Screen

5. Secondary Umbr ella Valve

6. Gerotor Fuel Pum p

7. Diverter Pipe

8. External Filter Screen

9. Jet Pump Filter Screen

10. Pressure Re lief Valve

Fuel Pres s ur e Re gula tor Assembly

The fuel pressure regulator is a part of the fuel

sender assem bly fuel r eturn pipe . It is a diaphragm

operated relief valve. A soft ware bias com p ensat es

the injector on-time because the fuel pressure

regulator is not referenced to manifold vacuum.

The fuel injector pulse width varies with the signal

fr om the MAP s ensor . Wit h the ignitio n ON and the

engine OFF, system fuel pressure at the pressure

test connection should be 380- 440 kPa ( 55-62 psi).

If the pressure is too low, poor performance could

result. If the pressure is too high, excessive odor

and a Diagnostic Trouble Code (DTC) P0132,

P0152, P0172, or P0175 may result. Refer to Fuel

System Diagnosis in Section 6C3-2A

DIAGNOSTIC TABLES – GEN III V8 Engines of

this Service Information CD for information on

diagnos ing fuel pr essure conditions.

Fuel Pump Stra ine r

The f uel pum p s trainer attac hes to the lower end of

the fuel pump and the lower end of the fuel return

pipe. The fuel pump strainer is made of woven

plast ic. T h e funct ions of t he fu el pump s trainer is to

filter contaminant s and to wick fuel.

The fuel pump strainer is self-cleaning and

normally requires no maintenance. Fuel stoppage

at this point ind icates tha t the fuel tank contains an

abnormal amount of sediment or water. Clean the

fuel tank and replace fuel sender assembly.

In-Line Fuel Filter

The fuel f eed pipe has a steel filter installed ahead

of the fuel injection system. The paper filter

element (2) traps particles in the fuel that may

damage the injection system. The filter housing (1)

is made to withstand maximum fuel system

pressure, exposure to fuel additives, and changes

in temperature. The inlet fitting is a quick-

disconnect and a the outlet is a threaded fitting

which is sealed with an O-ring. The fuel filter is to

be changed at prescribed service intervals, refer to

Section OB, Lubrication & Service of the VT

Series II Service Information. A restricted fuel filter

shou l d be replac ed.

Fuel Feed and Return Pipes

The fu el fee d pipe car ries f uel f rom the f uel tank to

the fuel rail assembly. The fuel return pipe carries

fuel from the T -connector located on the outlet side

of t he fuel f ilter back to t he fu el ta nk . The fu el pipes

cons ist of three sections:

• The rear fue l pipe assemblies are located from

the top of the fuel tank to the chassis fuel

pipes. The rear fuel pipes are constructed of

nylon.

• The chassis fuel pipes are located under the

vehicle and connect the rear fuel pipes to the

engine compartment connecting fuel pipe.

These pipes are constructed of steel.

• The engine compartment connecting fuel pipe

connects the chassis fuel pipe to the engine

fuel rail. T his fu el pi pe is constructed of nylon.

In-line Fuel Filter

1. Fuel Filter Housing

2. Paper Filter Element

Nylon Fuel Pipes

CAUTION: In order to Reduce the Risk of Fire

and Personal Injury:

• If nylon fuel pipes are nicked, scratched or

damaged during installation, Do Not

attempt to repair the sections of the nylon

fuel pipes. Replace them.

• When installing new fuel pipes, Do Not

hammer directly on the fuel harness body

clips as it may damage the nylon pipes

resulting in a pos sible l eak.

• Always cover nylon vapour pipes with a

wet towel before using a torch near them.

Also, never expose the vehicle to

temperatures higher than 115°C (239°F) for

more than one hour, or more than 90°C

(194°F) for any extended period.

• Before connec ting fuel pipe fittings, alw ays

apply a few drops of clean engine oil to the

male pipe ends. This will ensure proper

reconnection and prevent a possible fuel

leak. During normal operation, the O-rings

located in the female connector will swell

and may prevent proper reconnection if not

lubricated.

Nylon fuel pipes are designed to perform the sam e

job as the steel or flexible fuel pipes or hoses that

they replace. Nylon pipes are constructed to

withstand maximum fuel system pressure,

exposure to fuel additives, and changes in

temperature. There are three sizes of nylon pipes

used: 3/8” ID for the fuel feed, 5/16” ID for the fuel

return, and 1/2" ID for the vent

Heat resistant rubber hose and/or corrugated

plastic con duit pro tect the section s of the pipes that

are exposed to chafing, high temperature or

vibration.

NOTE: Nylon fuel pipes are som ewhat flexible and

can be formed around gradual turns under the

vehicle. Howeve r, if nylon f uel pipes a re forc ed into

sharp be nds, the pipes will kin k and restric t the fuel

flow. Also, once exposed to fuel, nylon pipes may

become stiffer and are more likely to kink if bent

too far. Take special care when working on a

vehicle with nylon fuel pipes.

Fuel Filte r Locati on View

1. Q uick Connect, F uel Tank Vapour Line to Caniste r

2. Hos e, Filler Neck Breather

3. Flexible Line, Fuel Feed to Engine

4. Quick Connect, Fuel Feed Line

5. Q uick Connect, F uel Filter T-piece

6. Ret aining Tangs, Fuel Filter Strap

7. Filter, Fuel

8. Quick Connect, Fuel Fee d Line fro m Fue l Tank

Quick-Connect Fittings

Quick -co nnect f ittings provide a sim plif ied m eans of installing and conn ecting f uel system com ponents . The fit tings

cons ist of a unique female connector and a compatible male pipe end. O-rings, located inside the f emale c onnecto r ,

provide the fuel s eal. Integral locking tabs or fingers hold the f ittings toge ther.

Fuel Pipe O-Rings

O-r ings s ea l the thr eade d c on nec tio ns in the f uel system and are mad e of sp ec ial m a ter ial. Ser vice the O -r ing s eals

with the correct servic e part.

Evapo rativ e Pipes and Hoses

The evaporative pipes extend from the fuel sender assembly and the evaporative canister vent solenoid to the

evaporative canister. The evaporative purge pipe extends from the evaporative canister to the evaporative purge

valve in the engine compartment. The rear pipes and the engine compartment pipe are constructed of nylon. The

chas sis evapora tive purge pipe is constructed of steel.

FUEL MET ERING MO DES OF O PERATION

Modes Of Ope ration

The PCM looks at voltages from several sensors to determine how much fuel to give the engine. The fuel is

delivered under one of several conditions called modes. The PCM controls all modes.

Starting Mode

Wit h the ign ition s witch in the O N po sition (b ef ore en gaging the st arter ), t he PCM ene rgis es the fuel pum p relay f or

two seconds, allowing the fuel pump to build system pressure. The PCM first checks speed density, then switches

to t he Mass Air Flow (MAF) sensor. T he PCM als o uses th e Engine Coolant T em perature (E CT), T hrottle Posit ion

(TP) , and Manif old Absolute Pres sure (MAP) sensors to dete rmine the proper air/fue l ra tio f or star ting. This ranges

from 9.7:1 to 14.7:1 depending on coolant temperature. The PCM controls the amount of fuel delivered in the

star ting mo de by changing the pulse width of the injectors. This is done by pulsin g the injectors for very short times.

Clear Flood Mode

If t he engine floods, clear the engine by press ing the accele rator pedal down all the way. The PCM then pu lses the

injec tor s at an air/ f uel ratio of 2 0: 1. T he PC M ho lds this inj e ctor r ate a s long as the thr ot tle stays wide open an d the

engine speed is below 300 RPM. If the throttle position becomes less than 80 percent, the PCM returns to the

starting mo de.

Run Mode

The r un m ode has two conditions called Open Loop, and Close d Loop. When th e engine is firs t sta rted, and engine

speed is above a predet ermined RPM, the system begins O pen Loop opera tion. The PCM ignores t he signal fr om

the Hea ted O xygen Senso r (HO 2S) and c alculates the air /f uel rat io based on inputs f rom the ECT , MAF, MAP, and

TP sensors. The sy stem stays in Open Loop until meeting the following conditions:

• Both HO 2S have varying voltage output, showing that they are hot enoug h to operate prope rly. (T his depends

on te mperature.)

• The Engine Collan t Temperature (ECT) s ensor is above a specified temperatur e.

• A spec ific amount of time has elapsed after starting the engine.

Specific values for the above conditions exist for each different engine, and are stored in the Electrically Erasable

Programmable Read Only Memory (EEPROM). The system begins closed loop operation after reaching these

values. In Closed Loop, the PCM calculates the air/fuel ratio (injector on-time) based on the signal from various

sensors, but mainly the HO 2S. T his allows th e air /fuel r atio to stay very close to 14.7:1.

Acceleration Mode

W he n the drive r presse s on the ac celerator pedal, air flow into the cylinder s increases rapidly, while fuel flow tends

to lag behind. To prevent possible hesitation, the PCM increases the pulse width to the injectors to provide extra

fuel ac celerat ion. The PCM det erm ines the am ount of fuel requir ed based on throttle pos ition, coola nt tempe ratur e,

m anifold air pr essure, mass air flow and engine speed.

Decele r ation Mode

When the driver releases the accelerator pedal, air flow into the engine is reduced. The PCM looks at the

corresponding changes in throttle position, manifold air pressure and mass air flow. The PCM shuts OFF fuel

com pletely if the decelerat ion is very rapid, or f or long p eriods (such as long c losed throttle c oast- down). T he fuels

shuts O FF in order to protect the warm-up three-way catalytic converters .

Battery Voltage Correct ion Mode

When battery voltage is low, the PCM compensates for the weak spark delivered by the ignition system in the

following ways:

• Inc r easing th e amoun t of fuel delivered.

• Increasing the idle RPM.

• Increasing ignit ion dwell time .

Fuel Cut OFF Mode

To prevent possible engine damage from over-speed, the PCM cuts off fuel from the injectors when the engine

speed is above approximately 6200 RPM. Also, see Rapid Deceleration in Deceleration Mode.

FUEL METERING SYSTEM COMPONENT DESCRIPTION

The fuel m ete ring s ystems c onsist s of the following

parts:

• The fuel supply components(fuel tank, pump,

pipes).

• The fuel pump elec trical circuit.

• The fuel rail.

• The fuel injectors.

• The fuel pr essur e regulat or.

• The throttle body.

• The Idle Air Contro l (IAC) valve.

• The Throttle Position Sensor.

System Overview

An electric fuel pump, located in the fuel tank with

the fuel sender assembly, supplies fuel through an

in-line fuel filter at a pressure greater than is

needed by the injectors. The fuel pressure

regulator, part of the fuel sender assembly, keeps

fuel available to the injectors at a regulated

pressure. A separate pipe returns unused fuel to

the fuel tank.

Fuel Pump Electrical Circuit

When the ignition switch is in the ON position

(before engaging the starter), the PCM energises

the fuel pump relay for two seconds, causing the

fuel pump to pre ss ur is e the f u el system . If the PCM

does not receive ignition reference pulses (engine

cranking or running) within two seconds, it shuts

OFF the f uel pump relay, c ausing the fuel pum p to

stop.

Fuel Rail Assembly

The fuel rail as sembly attaches to the en gine intak e

m anifold and performs the following functions:

• It positions the injectors (1) in the intake

manifold.

• It distr ibutes fuel evenly to the injectors.

• It integrates the fuel pulse dampener into the

fuel me tering system.

GEN3 0029

Fuel Rail Assembly

1. Fuel Injector

2. Fuel Pulse Dampener

3. Fuel Rail

Fuel Injec tors

The top-feed fuel injector assembly is a solenoid

operated device, controlled by the PCM, that

m eters p ressu rised f uel to a single en gine cylinder.

The PCM energises the injector solenoid, which

opens a ball valve, allowing fuel to flow past the ball

valve, and through a recessed flow director plat e.

The director plate has multiple machine holes that

control the fuel flow, generating a conical spray

pattern of finely atomised fuel at the injector tip.

Fuel is directed at the intake valve, causing it to

become further atomised and vaporised before

enter ing the co mbustio n cha mber . An injec to r st uc k

partly open can cause a loss of pressure after

engine shutdown. Consequently, long cranking

tim es would be notic ed on som e engines.

GEN3 0030

Fuel Inje ctor

Fuel Puls e Da mpe ner

The fu el puls e dam pener att aches inside a housing

on the f uel rail as sem bly. The fue l pulse dam pener

is diaphr agm operate d, with f uel pum p pres sure o n

one s ide and spr ing pre ssur e of th e other side. T he

function of the dampener is to reduce fuel

pulsat ion.

GEN 3 00 31

Fuel Pul se Dampener

Accelerator C ontrol s

The accelerator control system is cable operated.

Two different type of accelerator control cable

systems are used, one where Electronic Traction

Control (ETC) is fitted and the other without ETC.

Therefore use the specific cable for each

application. Cable adjustment is provided on the

throttle cable, refer to Section 6C3-3 SERVIE

OPERATIONS – G EN III V8 Engine of this Servic e

Information CD.

Throttle Body Assembly

The throttle body assembly attaches to the intake

manifold and controls air flow into the engine,

there by c ontrolling engine output . The dr iver opens

the throttle valve within the throttle body through the

acce lerator c ontrols. During engine idle, t he throttle

valves are almost closed. A fixed air bypass orifice

and the Idle Air Control (IAC) valve (3) control the

air f low.

Engine c oolant f lows thr ough a coolant cavity in the

bottom of the throttle body and prevents throttle

valve icing during cool weather operation. The

throt tle body also provid es the locati on for mount in g

the Throttle Position (TP) sensor ( 1).

Throttle Body Assembl y

1. TP Sensor

2. Throttle Body Assembly

3. IAC Valve

Throttle Position (TP) Sensor

The T hr ot tle Position ( TP) s ens or is m o unted to th e

throttle shaft on the throttle body. The T P sensor is

a potentio m e ter which is s upp lied a 5 volt reference

and an earth circuit from the PCM. The signal

circuit connects from a sliding contact in the TP

sensor to the PCM. This allows the PCM to

measure the voltage from the TP sensor. As the

throttle is depressed, the output of the TP sensor

changes. At a closed throttle position, the outp ut of

the T P sen sor is be low 1.25V. As t he throttle valve

opens, the output increases. At a wide-open

throttle, the TP sensor output voltage should be

greater than 4 volts.

Speed Density System Description

Three specific data sensors provide the PCM with

the basic information for the fuel management

portion of its operation. That is, three specific

signals to the PCM esta blish the en gine speed and

air density factor s. Th e engine s peed signal come s

fr om the ignition system .

The PCM us es this infor mation to determine eng ine

speed (RPM). Air density is derived from IAT and

MAP sensor inputs. The IAT sensor measures the

air tem per ature that is enter ing the eng ine. Th e IAT

signal works in conjunction with the MAP sensor to

determine air density. As the intake manifold also

increases and additional fuel is required. This

inform ation f rom the IAT an d MAP sensors is used

by the PCM to control injector pulse width.

The speed density system is used to :

1. Monitor Mass Air Flow (MAF) sensor operation

(to determine if there is a MAF sensor

malfunction).

2. T ake over f ueling manage m e nt oper atio n when

there is a Mass Air Flow (MAF) sensor

malfunction.

GEN3 0032

Throttle Position ( T P) Se nsor

1. Throttle Body

2. IAC Valve O-Ring

3. IAC Valve

4. IAC Valve Attaching Screws

5. TP Sensor Attaching Screws

6. TP Sensor

7. TP Sensor Seal

Short Term Fuel Trim Description

The short term fuel trim is a PCM erasable memory register. The neutral value for the short term fuel trim is 0%.

Any deviation from 0% indicates the short term fuel trim is changing the injector pulse width. The amount of pulse

width c hange de pends on how far the short term fuel trim valu e is from 0%. The short term fu el trim is rich when the

scan tool indicates -99%.

The short fuel trim is lean when the scan tool indicates 99%. The short term fuel trim changes the pulse width by

varying the Closed Loop factor of the base pulse width e quation.

As the PCM monitors the oxygen sensors input it, is constantly varying the short term fuel trim vale. The value is

updated very quickly, therefore, the shor t ter m fuel trim only corrects for short te rm mixture tre nds. T he corr ection of

long ter m mixture tren ds is the f unction of long term fuel trim.

When the PCM determines t hat the Short Term Fuel T r im is ou t of the operating range, the following DTCs will s et:

• DTC P0171: Bank 1 Too Lean

• DTC P0172: Bank 1 Too Rich

• DTC P0174: Bank 2 Too Lean

• DTC P0175: Bank 2 Too Rich

Long Term Fuel Trim Description

The long term fuel trim is a matrix of cells arranged by RPM and MAP. Each cell of the long term fuel trim is a

register like t he s hor t t erm f u el tr im . As the engin e ope rat ing c ondition s ch ang e, the PCM will switch fr om c ell to ce ll

to determine what long term fuel trim factor to use in the base pulse width equation.

While in any given cell, the PC M also m onitors the short term fuel t rim . If the shor t term f uel trim is f ar enoug h from

0%, the PCM will change the long term fuel trim value. On ce the long term fuel trim value is chan ged, it shou ld force

the short term fuel trim back toward 0%. If the mixture is still not correct (as judged by the HO2S), the short term

fuel trim will continue to have a large deviation from the ideal 0%.

In this case, the long term fuel trim value will continue to change until the short term fuel trim becomes balanced.

Both the short term fuel trim and long term fuel trim have limits which vary by calibration. Both the short term fuel

trim and long term fuel trim have limits that var y by calibration. If the mixt ur e is so far out of range that the long term

fuel trim reaches th e lim it of control withou t correcting the condition, the shor t term f uel trim will also go to its lim its

of control in the same direction. If the mixture is still not corrected by both short term fuel trim and long term fuel

trim at their extreme values, a Fuel T rim Diagnost ic Trou ble Code (DTC) will likely result .

When the PCM determines t hat the Long Term Fuel Trim is out of the operating ra nge, the following DTC s will s et:

• DTC P0171: Bank 1 Too Lean

• DTC P0172: Bank 1 Too Rich

• DTC P0174: Bank 2 Too Lean

• DTC P0175: Bank 2 Too Rich

Under the conditions of power enrichment, the PCM sets the short term fuel trim to 0% and freezes it there until

power en richment is no longer in effe ct. This is done so the Closed Loop factor and the long term fuel trim will not

try to correct for the com man ded richness of power enrichment.

1.5 IDLE AIR CONTROL (IAC) VALVE

The purpose of the Idel 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 a portion of

the bypass air . An orifice loc ated in th e throt tle body

also supplies a constant amount of bypass air.

By moving a conical valve, known as a pintle, in

towards the seat ( to decre ase air f low); or out away

from the seat (to increase air flow), a controlled

amount of air can be bypassed. If engine speed is

too low, more air is bypassed to increase RPM. If

engine speed is too high, less air is bypassed to

decrease RPM.

The PCM moves the IAC valve in small steps,

called counts. These can be measured and

displayed by a Tech 2 scan tool, which plugs into

the Data Link Connector (DLC). The PCM

calculates the proper position of the IAC valve

during idle, based on battery voltage, coolant

temperature, engine load, and engine RPM. If the

RPM drops below specification and the throttle

valve is closed, the PCM senses a near stall

condition and calculates a new valve position in

order to prevent stalling.

• Engine idle speed is a func tion of total air flo w

into the engine. Idle speed is based on IAC

valve pintle position + crankcase ventilation

valve flow + throttle valve opening + bypass

orifice air flow + calibrated vacuum loss

thr ough accessories.

• Controlled idle speed is programmed into the

PCM, which determines the correct IAC valve

pintle position to maintain the desired idle

speed for all engine operating conditions and

loads.

GEN3 0033

Idle Air Cont rol (IAC) Valve Air Flow

1. IAC Valve

2. Throttle Plate

3. IAC Valve Pintle

• The minim um idle air rate is set at the factory

with a stop screw. This setting allows enough

air flow by the throttle valve to cause the IAC

valve pintle to be positioned a calibrated

number of steps (counts), from the seat,

durin g controlled idle operation.

IDLE AIR VALVE POSITION RESET

If the IAC valve is disconnected and reconnected

with the engine running, the idle speed may be

wrong. If this occurs, reset the IAC valve by

depressing the accelerator pedal slightly, start and

run the engine for five seconds, then turn the

ignition OFF for ten seconds.

IAC Valve Location

1. TP Sensor

2. Throttle Body

3. IAC Valve

1.6 ELECTRONIC IGNITION SYSTEM

IGNITION SYSTEM OVERVIEW

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 PCM controls the spark advance of the ignition system. The Electronic ignition system has the

following advantages over a mechanical distributor system:

• No moving parts.

• Les s maintenanc e.

• Remote mounting capability.

• No mechanical load on the engine.

• More coi l cool down time be t w e en firing events.

• Elim ination of mec hanical timing adju s tments.

• Incr eased available ignition coil satur at ion time .

The ele ctr on ic ignit ion s ystem d oes not us e the co nventi onal dis t ribu to r a nd c oil. The ignitio n system co ns ists of the

following components/circuits:

• Eight ignition coils/modules

• Eight Ignition Control (IC) circuits

• Camshaft Position (CMP) sensor

• 1X Camshaft reluctor wheel

• Cranksh aft P os ition (CKP) se ns or

• 24X Crankshaft reluctor wheel

• Related connecti ng wire s

• Powertrain C ontrol Module (PCM)

COMPONENTS

Crankshaft Position Sensor (CKP) and Reluctor Wheel

The Crankshaft Position (CKP) sensor is located in

the right r ear of the engine, behind the s tarter and is

a dual m agnet o re sis tive type sens or . T his sens or is

not speed dependent. The dual micro switches

monitor both notches of the reluctor wheel for

greater accuracy. The CKP sensor works in-

conjunction with a 24X reluctor wheel.

The reluctor wheel is mounted on the rear of the

crankshaft. The 24X reluctor wheels use two

different width notches that are 15 degrees apart.

This pulse width encoded pattern allows cylinder

position identification within 90 degrees of

crankshaft rotation. In some cases, cylinder

identification can be located in 45 degrees of

crankshaft rotation. This reluctor wheel also has

dual track notches that are 180 degrees out of

phase. The dual track design allows for quicker

starts and accuracy.

The PCM also receives a 4X signal from the

crankshaf t pos it ion se nso r. T h e PCM u tilis es the 4X

signal for the following:

• Misfire

• Tachometer output

• Spark control

• Fuel Control

• Certain diagnostics

The CKP signal m ust be available for the engine to

start. The CMP signal is not needed to start and

operate the engine. T he PCM can determine when

a particular cylinder is on either a firing or exhaust

stroke by the 24X signal. The CMP sensor is to

determine what stroke the engine is on. The

system will attempt to synchronise and look for an

increa se in the MAF s ignal. An increase in the MAF

signal indicates the engine has started. If the PCM

does not detect an increase in the MAF signal, a

re-sync will occur to the opposite cam position. A

slightly longer cranking time may be a symptom of

this condition.

Crankshaft Positi on Sensor and Rel uctor Wheel

1. CKP Sensor

2. Reluctor Wheel

Camshaft Position Sensor (CMP)

The Camshaft Position (CMP) sensor is mounted

through the top of the engine block at the rear of

the valley cover. The CMP sensor works in-

conjunction with a 1X reluctor wheel. The reluctor

wheel is located at the rear of the camshaft. The

CMP sensor is used to determine whether a

cylinder is on the firing or the exhaust stroke. As

the cam s ha f t rot ates , t he relu ctor wheel interr u pts a

magnetic field produced by a magnet within the

sensor. The CMP sensor internal circuitry detects

this and produces a signal which is used by the

PCM. The PCM uses this signal in combination

with the CKP 24X signal to det ermine to crank shaft

posit ion and stroke.

The CKP signal m ust be available for the engine to

start. The CMP signal is not needed to start and

operate the engine. T he PCM can determine when

a particular cylinder is on either a firing or exhaust

stroke by the 24X signal. The CMP sensor is to

determine what stroke the engine is on. The

system will attempt to synchronise and look for an

increa se in the MAF s ignal. An increase in the MAF

signal indicates the engine has started. If the PCM

does not detect an increase in the MAF signal, a

re-sync will occur to the opposite cam position. A

slightly longer cranking time may be a symptom of

this condition.

GEN3 0022

Camshaft Position (CMP) Sens or

1. CMP Mou nting Bolt

2. CMP Sensor

3. Top Rear of Engine Block

Ignition Coils/ Module

The ignition system on this engine features a

m ultiple coil ignition and is k nown as coil near plug.

The secondary ignition wires are short compared

with a distributor ignition system wire. Eight ignition

coils/m odules are individually mounted above each

cylinder on the rocker covers and fire sequentially.

There is an Ignition Control (IC) circuit for each

ignition coil/module. The eight ignition control

circuits are connected to the PCM. All timing

decisions are made by the PCM, which triggers

each co il/module individually.

The ignition coil/ modules are supplied with the

following circuits:

• Ignition feed circuit

• Ignition control circuit

• Earth circuit

• Reference low circuit

Ignition Coils/Module Location

Ignition Coils

The ignition feed circuits are fused separately for

each bank of the engine. Th e two f uses also supply

the injectors for that bank of the engine. Each

coil/module is serviced separat ely.

This system puts out very high ignition energy for

plug firing. Because the ignition wires are shorter,

less energy is lost to ignition wire resistance. Also,

since the f iring is sequen tial, each coil has f ar m ore

tim e to s aturate as oppos ed to the t hree in a waste

spark arrangement. Furthermore, no energy is lost

to the resistance of a waste spark sy stem.

CIRCUITS AFFECTING IGNITION CONTROL

To properly control ignition timing, the PCM relies

on the following informa tion:

• Engine load ( manifold pressure or vacuum )

• Atmospher ic ( barometric) pressure

• Engine temper ature

• Intake air t empe rature

• Cranksh aft posit i on

• Engine s peed (RPM)

The Ignition Control (IC) system consists of the

following components:

• Ignition coil/modules

• 24X crankshaft position sensor

• Powertrain C ontrol Module (PCM)

• All connect ing wir es

Ignition Coils/Modules

1. Ignition Coils/Modules

2. Engine Valve Cover

The Ignition Control utilises the following to control

spark timing functions:

• 24X signal: The 24X crankshaft position

sensor sends a signal to the PCM. The PCM

uses this signal to determine crankshaft

position. The PCM also utilises this signal to

trigger th e fuel injectors.

• Ignition Control (IC) circuits: The PCM uses

these circuits to trigger the ignition

coil/modules. The PCM uses the crankshaft

reference signal to calculate the amount of

spark advance need ed.

NOTEWORTHY IGNITION INFORMATION

Ther e are import ant c on side rat ion s to point o ut when s er vic ing the ignit ion s ystem . The f ollowing inf or m a tion will list

some of these, to help technician in servicing the ign ition system.

• Th e ignition coil’s se condar y voltage outp ut capa bility is very high - m ore than 40,000 volts. Avoid body contact

with ignition hig h voltage secondary c ompon ents when the engine is running, or personal injury may result.

• Th e 24X cr ank sha ft p osition sens or is the m ost critic al part of the ignition system . If the sens or is dam ag ed so

that pulses are not generated, the engine will not start.

• Crankshaft position sensor clearance is very important. The sensor must not contact the rotating interrupter

ring at any time, or sensor damage will result. If the interrupter ring is bent, the interrupter ring blades will

destroy the sensor.

• Ignition timing is not adjusta ble. There are no timing marks on the crankshaft balancer or timing chain cover.

• Be care fu l not t o dam ag e th e sec on dar y ignition wires or bo ots when serv icing the ignition system. Rota te each

boot to dis lodge it f r om t he pl ug or c oil t ower bef o re pullin g it fr om eith er a spark plug or the ignition coil. Never

pierc e a sec ondar y ignition wire or boot f or any testing purpose s! Futu re problem s will occur if pin points or tes t

lights are pushed through the insulating fo r testing.

POWERTRAIN CONTROL MODULE (PCM )

The PCM is respons ible for maintaining correc t spark and fue l injection timing for all d riving conditions. To pro vide

optimum driveability and emissions, the PCM monitors input signals from the following components in calculating

Ignition Control (I C) spark timing:

• Engine Coolant Temp er ature (ECT) sensor

• Intake Air Temperature (IAT) sensor

• Mass Air Flow (MAF) sensor

• Automatic Transmission R ange inputs from the T r ansmission Range switch

• Throttle Position (TP) sensor

• Vehicle Speed Sensor (VSS)

RESULTS OF INCORRECT OPERATION

An ignition control circuit that is open, earthed, or short circuited will set an ignition control circuit DTC. If a fault

occu rs in the IC output circuit when the eng ine is running, the engine will experienc e a mis fir e. DT Cs P0351-P0358

will set when a m alfun ction is dete cted with an Ignit ion Co ntrol cir cui t. When an Ignit ion c ontrol DT C s ets , th e PCM

will disabled the injector for the appropriate cylinder.

The PCM uses information from the engine coolant temperature sensor in addition to RPM to calculate spark

advance values as follows:

• High RPM = m ore advance

• Cold engine = more advance

• Low RPM = less advance

• Hot engine = less advance

Therefore, detonation could be caused by high resistance in the engine coolant temperature sensor circuit. Poor

performance could be caused by low resistance in the engine coolant temperature sensor circuit.

If the e ngine c rank s b ut will not run o r im m ediately sta lls, Engine Crank s But Will Not Run diagnost ic table m us t be

used to determine if the failure is in the ignition system or the fuel system. If DTC P0341, P0342, P0343, P0335,

P0336 is set, the appropriate diagnostic trouble code table must be used for diagnosis.

1.7 CRANKCASE VENTILATION SYSTEM

A closed crankcase ventilation system is used to

provide a more complete scavenging of crankcase

vapours . F re sh air f ro m t he thr o ttle bod y is supplied

to the crankcase, mixed with blow-by gases and

then passed through a crankcase ventilation valve

into the intake manifold.

The primary control is through the crankcase

ventilation valve which meters the flow at a rate

depending on manifold vacuum. To maintain idle

quality, the crankcase ventilation valve restricts the

flow when intake manifold vacuum is high. If

abnormal operating conditions arise, the system is

designed to allow excessive amounts of blow-by

gases to back flow through th e cr ank case vent tube

into the engine air inlet to be consumed by normal

combustion.

The engine ventilation system was developed to

minimise oil consumption and ensure that oil

ingestion could not occur during high speed

cornering manoeuvres. Filtered fresh air is routed

from up stream of the throttle blade to the front of

the right rocker cover via a form ed rubber hose.

To reduce the potential of oil pullover into the

throt tle bor e area due to back flow of t he ventilat ion

system, the fitting in the right side rocker cover is

located between a shield from the rocker arms.

Blow-by gases are routed from the rear of both

rock er cover s, th rough m oulde d nylon lines to a tee

fitt ing located o n the centr eline of th e engin e at th e

rear of the intake manifold. From there, a single

nylon line carries the gases through an externally

mounted, horizontal PCV valve and enters the

intake manifold behind the throttle body.

The dual draw system was developed to meet

vehicle m anoeuvre requirements. During sustained

m ax im u m later al acc ele rat ions , the outb oar d roc k e r

cover may fill with oil. The dual draw system

pass ively switches , allowing the PCV valve to draw

on the rocker cover with the least resistance. This

results in the system drawing on the air filled, or

inboard rocker cover and eliminates oil pullover due

to drawing on th e oil-fil led outboard rocke r co v e r.

T20B009

Crankcase Ventilation System Routing

1. PCV Valve

2. Throttle Body

3. Fresh air

4. Return air

1 4

RESULTS OF INCORRECT OPERATION

A plugged PCV valve or hose may cause:

• Rough idle.

• Stalling or slow idle speed.

• Oil leaks.

• Sludge in engine.

A leaking valve or hose would cause:

• Rough idle.

• Stalling.

• High idle s peed.

For re placement of the PCV and related crank case

hoses, refer to Section 6E3 Emission Control -

GEN III V8 Engine of the VT Series II Service

Information.

GEN3 0038

PCV Cutawa y

1. Check Valve

1.8 EVAPORATIVE EMISSION

The Evaporative Emission Control System (EECS)

used on this vehicle is the charcoal canister

storage met hod. T his m ethod tran sfers f uel vapour

fr om the f uel t ank to an activat ed carb on (c harcoa l)

storage device (canister located under the rear of

the veh icle) to hold t he vapour s when the vehic le is

not oper ating. W hen the engine is running, the fuel

vapour is purged from the c arbon element by intake

air flow and consumed in the normal combustion

process.

The EECS purge solenoid valve allows manifold

vacuum to purge the canister. The Powertrain

Control Module (PCM) supplies an earth signal to

energise the EECS purge solenoid valve (purge

ON). The EECS purge solenoid control is Pulse

Width Modulated (PWM) or turned ON and OFF

several times a second.

The PCM controlled PWM output is commanded

when the appr opriate conditions have been met:

• Engine coolant temperature is below 30°C at

cold st art up.

• Engine has been running longer than 2

minutes.

• Engine coolant temperature is above 30°C at

warm star t up.

• Engine has been running longer than 30

seconds.

• Engine is not in Decel Fuel Cutoff Mode.

• Throttle opening is less than 96%.

• Engine is in Closed Loop mode or Open Loop

mode.

A higher purge rate is used under conditions that

are likely to produce large amounts of vapour,

when the fo llowing conditions have been met:

GEN3 0039

Fuel Vapour Canister

1. Air Vent Port

2. Canis ter Purge Port

3. Vapour From Fuel Tank Po rt

4. Vapour Canister

• Intake Air Temperature (IAT) is above 50 °C.

• Engine Coolant Temperature (ECT) is above

100°C.

• Engine has been running for more than 15

minutes.

EECS purge PWM duty cycle varies according to

operating conditions determined by mass air flow,

fuel trim and intake air temperature. The EECS

purge will be re-enabled when TP angle decreases

below 96%.

The canister ( loca ted u nder the re ar of the vehicle)

cannot be repaired, and is serviced only as an

assembly. Periodically check the canister at the

time or distance intervals specified in

Section OB LUBRICATION & SERVICE of the VT

Series II Service Information or the Owner’s

Handbook.

Canister Purge Solenoid Location

1. Evaporative Purge Solenoid

The fuel vapour canister is mounted in a bracket

underneath the vehic l e, located by the fuel filter.

This canister is a three port design. Fuel vapour is

absor bed by the c harc oal within the canist er. Whe n

the engine is running at idle speed and above idle,

air is drawn into the canister through the air vent

port (atmospheric port) at the top of the canister

assembly. The air mixes with the fuel vapour and

the mixture is drawn int o the in take manifold via the

canister purge line.

The Up perm ost port on t he canis ter is con trolled by

a PCM controlled canister purge solenoid. The

canister purge solenoid controls the manifold

vacuum signal from the throttle body. The port

below the canister purge port is the vapour inlet

from the fuel tank. The fresh air inlet port (air vent

port) on the canister is open to the atmospher e via

a hose t hat vents und er the vehicl e.

RESULTS OF INCORRECT OPERATION

• Poor idle, stalling and poor driveability can be

cause d by:

- Inoperative canister purge solenoid

- Damaged canister.

- Hoses split, cracked and/or not connected

to the

proper tubes.

- Throttle body and canister hoses

interchanged on the purge solenoid

connections.

NOTE: The canister connection is marked with

CAN.

• Evidence of fuel los s or fuel vapour odour can

be caused by:

Canister Location

1. Evaporati ve Canister ( Under Vehicle by Fuel T ank)

2. Fuel Filter

- Liquid fuel leaking fr om f uel lines.

- Cr acked or damaged c anister.

- Disconnected, incorrectly routed, kinked,

deteriorated or damaged vapour hoses, or

control hoses.

If th e solenoid is s tuck open, or the co ntrol cir cuit is

shorted to earth, the canister will purge to the

intake manifold all the time. This can allow extra

fuel at idle or during warm-up, which can cause

rough or unstable idle or a rich fuel operation.

If the canister purge solenoid is always closed, the

canister can become over loaded with fuel,

resulting in fuel odour.

A failure in the canister purge solenoid or circuit

may result in DTC P0443.

GEN 03 0042

123

Sectioned View of Canister

1. Air Vent Por t

2. Canister Purge Port

3. Vapour From Fuel Tank Port

4. Evaporative Canister

5. Volume Compensator

6. Charcoal Bed

GEN 3 0043

Typical Evaporative Emission Control Schematic

1. Throttle Body

2. Atmospheric Port Hose

3. Evaporative Emission Canister

4. Fuel Vapour Hose

5. Fuel Tank

6. Pressure/Vacuum Vented Fuel Filler Cap

7. Evaporative Purge Hose

8. Canister P ur ge Solenoid (Norm ally Close d)

1.9 ELECTRI C COOLING FANS

The GEN III engine has two, two speed electric

engine cooling fan assemblies that provide the

primary means of moving air through the engine

radiator. The cooling fans are used to cool engine

coolant flowing through the radiator and the

refrigerant flowing through the A/C condenser (if

fitted).

Each engine cooling fan motor has four terminals;

two negative and two positive. The two negative

terminals are the relay controlled circuits for fan

operation. The two positive terminals are the direct

power feed from a fusible link to the fan motors.

When an earth signal is applied to one of the

negative t erminals, the f an m oto r will operat e at low

speed. When an earth signal is applied to both

negative terminals, both fans will operate at high

speed.

The engine cooling fan high speed and low speed

relays are used to control the earth signal to the

electric motors.

The high speed relay is controlled by the PCM,

which cont rols the eart h path for the engine cooling

fan high speed relay.

The low speed of the electric fan is controlled by

the PC M through a spec ial Data Com m unication t o

the BCM. The BCM controls the earth path for the

engine cooling fan low speed relay.

The PCM determines operation of the two, two

speed engine cooling fans based on A/C request,

engine coolant temperature, A/C Refrigerant

Pressure Transducer, and vehicle speed signal

inputs.

There are also four (4) suppression capacitors

incorporated into the fan motor wiring circuits.

These suppression capacitors help eliminate fan

motor noise through the radio speakers. If these

capacitors are open, then noise will be present

through the radio speakers. If shorted to earth, the

fan motors could continuously run, or the fuse or

fusible link could fail.

For replacement of the cooling fan motor, refer to

Section 6B3 ENGINE COOLING of the VT Series

II Service Information.

T6B3001

Engine Cool in g Fan Assembly

1. Top of Radiator

2. Cooling Fan Mot ors

3. Cooling Fan Shroud

ENGINE COOLING FAN LOW SPEED

The engine cooling fan low speed relay is

energis ed by the BCM. Th e PCM det ermine s when

to enable the low speed fan based on inputs from

the BCM serial data, Engine Coolant Temperature

(ECT) sensor and the Vehicle Speed Sensor

(VSS).

The cooling fan low speed relay will be turned ON

when:

• The A/C requ est indicated ( YES) and either

• the vehicle speed is less than 30 km/h

• A/C pr essure is greater than 1500 kPa

• The coolant tem perature is greater than 98°C.

• If the coolant temperature is greater than

113°C when the ignition is switched OFF, the

relay is ener gised for up to approximately four

minutes.

• If an engine coolant temperature sensor fault

is detected, such as DTC P0117, P0118,

P1114, P1115.

The cooling f an low speed relay will be turned OFF

when any of the following conditions have been

met:

• The A/C requ est is not indicated (NO)

• The A/C request is indicated (YES) and the

vehicle speed is greater than 50 km/h, A/C

pressure is less than 1170 kPa, and coolant

temperature less than 98°C.

NOTE: T he low speed c ooling fan has a minim um,

run on time of 30 seconds.

Engine Fa n Low Speed Relay Locati on

1. Engine Fan Low Speed Relay

2. Engine Fan High Speed Relay

ENGINE COOLING FAN HIGH SPEED

The engine cooling fan high speed relay is

controlled by the PCM based on input from the

Engine Coolant Temperature (ECT) sensor.

The PCM will only turn ON the engine cooling fan

high speed relay fan if the engine cooling fan low

speed relay has been ON for 2 seconds and the

following co nditions are s atisfied:

• An Engine Coolant Temperature sensor fault

is detected such as DTC P0117, P0118,

P1114, P1115.

• Coolant temperature greater than 108°C.

The engine cooling fan high speed relay can also

be enabled by the A/C Refrigerant Pressure

Transducer. When the A/C Refrigerant Pressure

transducer determines the A/C system pressure is

too high (greater than 2400 kPa) and this will

instruct the PCM to enable the high speed fan.

If th e low speed fan was O FF when th e criteria was

met to turn the high speed fan ON, the high speed

fan will come ON 5 seconds aft er the low speed f an

is turned ON.

If both the engine cooling fan relays are ON, the

PCM will turn OFF the high speed re lay when:

• The engine coolant temperature is less than

102°C.

• A/C request not indicated (NO ).

• A/C r eques t indica ted ( YES) and A/C pres sur e

is less than 1900 kPa.

NOTE: The high speed coo ling fan has a minimu m,

run on time of 30 seconds.

1.10 A/C CLUTCH CONTROL

This vehicle uses two types of A/C clutch controls;

one with standard A/C and the other uses an

Electronic Climate Control (ECC) module.

ECC SYSTEM

With the ECC system, when the A/C is requested

the electronic climate control module will supply a

signal to the BCM. T he BCM will then send a serial

data request to the PCM. W hen the PCM receives

the serial data request on PCM terminal J1-58, it

indicates that air conditioning has been requested

and approximately 1/2 second after the PCM

receives this signal, it will energise the A/C control

relay. This serial data signal to the PCM is also

used to a djus t the idle sp eed bef ore tu rning O N the

A/C compressor relay. If this signal is not available

to the PCM, t he A/C compress or will be inoperative.

The BCM also supplies the earth signal from BCM

terminal 7 to the low speed cooling fan relay.

This A/C system also incorporates an A/C

Refrigerant Pressure Transducer. The A/C

Refrigerant Pressure Transducer signal indicates

high side refrigerant pressure to the PCM. The

PCM uses this information to adjust the idle air

control valve to compensate for the higher engine

loads present with high A/C refrigerant pressures.

A fault in the A/C Refrigerant Pressure T ransducer

signal will cause DTC P0530 t o set.

The PCM will not energise the A/C control relay if

any of the following conditions are present:

• High coolant temperature

• Low A /C sy stem pressure

• High A/C system pressure

• Wide open thrott l e

• High engine RPM

T26C3004

A/C Refrigerant Pressure Transducer Location

1. A/C Re frigerant Pres sure Tr ansducer

STANDARD A/C SYSTEM

On vehicles equipped with non-ECC systems the

power flow is different. With the blower fan

switche d O N, a nd the air c ond itioning swit ch ed ON,

switched ignition voltage is supplied from fuse F13

through the A/C master switch, and then to the

BCM. T he BCM will t hen s upply a serial data signal

to the PCM requesting A/C. If the BCM does not

receive a earth signal from the blower switch to

BCM terminal 3, the BCM will not supply the serial

data request for A/C. Once the PCM receives this

serial data signal, the PCM will energise the A/C

com press or re lay. T he BCM also supplies the earth

signal from BCM terminal 7 to the low speed

cooling fan relay.

This serial data signal to the PCM is also used to

adjust the idle speed before turning ON the A/C

compressor relay. If this signal is not available to

the PCM, the A/C compr essor will be inoperative.

This system, like on the ECC system also

incorporates an A/C Refrigerant Pressure

Transducer. The A/C Refrigerant Pressure

Transducer signal indicates high side refrigerant

pressure to the PCM. The PCM uses this

information to adjust the idle air control valve to

compensate for the higher engine loads present

with high A/C refrigerant pressures. A fault in the

A/C Refrigerant Pressure Transducer signal will

caus e DTC P0530 to set.

A/C Relay L ocation

1. A/C Relay

1.11 ELECTRONIC TRACTION CONTROL

PURPOSE

The Electronic Traction Control (ETC) system is

designed to maintain traction and reduce wheel

over- spin at the drive wheels on slippery surfaces

during acceleration. This system is designed to

operate at all vehicle speeds and reduces wheel

slip by use of the engine torque management

system, throttle relaxer control module and anti-

lock brake (ABS) system.

The ABS/ET C module m onitors both front and rea r

wheel speeds through the wheel speed sensors. If

at any time during acceleration the ABS/ETC

module detects drive wheel slip, it will request the

Powertrain Control Module (PCM) to bring excess

engine torque into a specific range, refer to

Section 12L ABS & ABS/ETC of the VT Series II

Serv i c e In format i on .

If the ABS/ETC cont inues to detect the rear wheels

are rotating faster than the front it will request the

throt tle relax er c ont ro l module to r edu ce t he thr o ttle

angle. The last measure taken to control the rear

wheels is for the ABS/ETC module to apply the rear

brakes, thus reducing torque to the r e ar wheels.

Once the rear wheels begin to rotate at the same

speed as the front wheels, the system will return full

control to the driver. During traction control mode, if

the brake is applied to only one drive wheel, most

of the torq ue fr om the engine will be dir ecte d to th e

other drive wheel which will improve the traction of

the vehicle .

ABS/ETC Module Loc at io n

1. ABS/ETC Hydraulic Modulator

2. Nut (2 Places) 5.0 - 12.0 Nm

The trac tion c ontrol b raking is accom plis hed by the

ABS/ETC module closing the isolation valves,

turning on the ABS pump motor and supplying

brake pres sure to the over spinning wheel(s ) .

The isolation valves isolate the front brake

hydraulic circuits from the m aster cylinder and rear

brake hydraulic circuits. Once the rear brake

hydraulic circuits are isolated, pressure can be

applied to the rear wheels without affecting any

other brake hydraulic circuits. The ABS/ETC

module turns on the ABS pump motor to apply

pressure, and begins cycling the ABS assembly's

inlet and outlet valves.

The inlet and outlet valve cycling aids in obtaining

maximum road surface traction in the same

manner as the anti-lock brake mode. The

difference between electronic traction control and

anti-lock br ake m ode is that brake fluid pres sure is

increased to lessen wheel spin (traction control

mode), rather then reduced to allow greater wheel

spin (anti-lock brake mode).

If at any time during traction control mode, the

brakes are manually applied, the brake switch

signals the ABS/ETC module to disable traction

contr ol mode and allow manu al br aking.

If there is a malfunction between the ABS/ETC

module and the PCM, DTC will set. If there is a

m alfunctio n between the ABS/ETC m odule a nd the

throttle relaxer control module, refer to

Section 12L ABS & ABS/ETC of the VT Series II

Serv i c e In format i on .

For further description on the Anti-Lock Brake

(ABS) system, Electronic Traction Control (ETC)

system and Throttle Relaxer Control Module

operation and DTC diagnosis, refer to

Section 12L ABS & ABS/ETC of the VT Series II

Serv i c e In format i on .

GEN3 0006

Throttle Relaxer Control Module

1. Throttle Re l ax e r Co nt ro l M od ule

2. Powertrain Inter fac e Module

3. Left F r ont Kick Pa nel

1.12 AIR INTAKE SYSTEM

The air intak e system draws out side air th rough th e

front of the air cleaner assembly and filter element

of the forward mounted air cleaner. The air is then

route d th rou gh the MAF sens or and in to the t hro tt le

body to the intak e m anif old. T he air is then direct ed

into the intake manifold runners, through the

cylinder heads and int o the cylinders.

If the Mass Air Flow (MAF) sensor is installed

backwards, the system will run rich. An arrow

marked on the plastic portion of the sensor

indicates correct air flow direction. The arrow must

point towar d the engine.

T26C3002

Air Cleane r Location

1. Air C leaner Housing

2. Mass Air Flow (MAF) Sensor

Air Cleaner Housing Assembly

1. Air Cleane r Ho usi n g U pp er Body

2. Air Cleaner Housing Top Cover Retaining

Screws (3)

3. Air Cleaner Filter

4. Air Cleane r Ho usi n g Lower Body

5. Mass Air Flow (M AF) Sensor

6. Air Intake to Throttle Body

7. Air Cleaner Housing Retaining Screws (3)

8. Air Inlet to Air Cleaner Housing Duct

9. Intake Air Temperature (IAT) Sensor

10. Intake Air Temperature (IAT) Sensor Clip

1.13 AUTOMATIC TRANSMISSION SENSORS & SIGNALS

1-2 (A) AND 2-3 (B) SHIFT SOLENOID VALVES

IMPORTANT: The shift solenoid valve resistance

should measure 19-24 ohms minimum when

measured at 20°C (68°F). The shift solenoid current

flow should not exceed 0.75 amps. The shift solenoid

should energise at a voltage of 7.5 volts or more

(measured across the terminals). The shift solenoid

should de-energise when the voltage is one volt or

less.

If both solenoid s lose power, only third gear engages.

The 1-2 and 2-3 shift solenoid valves (also called A

and B solenoids) are identical devices that control the

m oveme nt of t he 1-2 and 2- 3 shift valve s (the 3- 4 s hift

valve is n ot dir ectly controlled by a sh ift solenoid) . T he

solenoids are normally open exhaust valves that work

in four combinations to shift the transmission into

differen t ge a rs.

The PCM energises each solenoid by grounding the

solenoid through an internal quad driver. This sends

current through the coil winding in the solenoid and

m oves the internal plunger ou t of the exhau st position .

When ON, the solenoid redirects fluid to move a shift

valve.

IMPORTANT: The manual valve can hydraulically

override the shift solenoids. Only in D4 do the shift

solenoid states totally determine what gear the

tra nsmissio n is in. In the other m anual valve positions ,

the transmission shifts hydraulically and the shift

solenoid states CATCH UP when the throttle position

and the vehicle speed fall into the correct ranges.

Diagnostic trouble codes P0753 and P0758 indicate

shift solenoid circuit voltage faults.

The PCM-controlled shift solenoids eliminate the need

for throttle valve and governor pressures to control

shift valve operat ion.

8885

3-2 SHIFT SOLENOID VALVE ASSEMBLY

IMPORTANT: The 3-2 shift solenoid valve assembly

resistance should be a minimum of 20-24 ohms at

20°C (68°F).

The 3-2 shift solenoid valve assembly is an ON/OFF

solenoid that is used in order to improve the 3-2

downshift. The solenoid regulates the release of the 3-

4 clut ch and the 2-4 band apply.

If a voltage fault is detected in the 3-2 shift solenoid

circuit, diagnostic trouble co de P0785 will set.

325350

TRANSMISSION PRESSURE CONTROL SOLENOI D

IMPORTANT: Transmission pressure control solenoid

resistance should measure 3-5 ohms when measured

at 20°C (68°F).

The transmission pressure control solenoid is an

electronic pressure regulator that controls pressure

bas ed on the c urrent flow throug h its coil winding . The

magnetic field produced by the coil moves the

solenoid's internal valve which varies pressure to the

pressure regulator valve.

The PCM controls the pressure control solenoid by

comm an ding c urr ent between 10 0 and 1100 m illiamps .

Th is changes th e duty cycle of the so lenoid, which can

rang e between 5 per cent and 95 per cent ( typically less

than 60 percent). 1100 milliamps corresponds to

minimum line pressure, and 100 milliamps

corresponds to m aximum line pressure If the solenoid

loses power, the transmission defaults to maximum

line pressure.

The PCM commands the line pressure values, using

inputs such as the throttle position sensor. The

pres su re c ont ro l solen oid ta k e s the plac e of the throttle

valve or the vacuum modulator that was used on the

past model transmissions.

If the duty cycle drops below 5 percent or rises above

95 per cent, DT C P0748 will set.

325352

TORQUE CONVER TER CLU TCH SOLE N OID V ALVE

IMPORTANT: Th e TCC solenoid r esistanc e should be

21-2 6 ohm s m inimum when m easu red at 20°C (68°F).

If a fault is detected in the TCC solenoid circuit, code

P0740 will set.

The torque converter clutch solenoid valve is a

normally open exhaust valve that is used to control

torque converter clutch apply and release. When

grounded (energised) by the PCM, the TCC solenoid

valve stops converter signal oil from exhausting. This

causes converter signal oil pressure to increase and

shifts the TCC solenoid valve into the apply position.

Th e brake switc h is an input to the PCM, and the PCM

directly controls the TCC apply based on the brake

switch status.

8882

TORQUE CONVERTER CLUTCH PWM SOLENOID VALVE

IMPORTANT: TC C PWM solen oid valve resista nce

should be 10-11 ohms when measured at 20°C

(68°F), and 13-15 ohms when measured at 100°C

(212°F).

The torque converter clutch PWM solenoid valve

controls the fluid acting on the converter clutch

valve, which then controls the TCC apply and

release. This solenoid is attached to the control

valve body assembly within the transmission.

The TCC PWM solenoid valve provides smooth

engagement of the torque converter clutch by

operating on a negative duty cycle a variable

percent of ON time.

If a fault is detected in the TCC PWM circuit, code

P1860 will set.

325355

TRANSMISSION FLUID PRESSURE (TFP) MANUAL VALVE POSITION SWITCH

IMPORTANT: Seven valid combinations and two

invalid combinations are available from the TFP

manual valve position switch. Refer to the TFP

Manual Valve Position Switch Logic table below for

valid/invalid combinations for range signal circuits

A, B and C.

Gear Positi on Range Sig nal A Range Signa l B Range Signal C

Park Open 12 V Closed 0 V Open 12 V

Reverse Closed 0 V Closed 0 V Open 12 V

Neutral Open 12 V Closed 0 V Open 12 V

D Open 12 V Closed 0 V Closed 0 V

3 Op en 12 V Open 12 V Closed 0 V

2 Open 12 V Open 12 V Open 12 V

1 Closed 0 V Open 12 V Open 12 V

Invalid Closed 0 V Open 12 V Closed 0 V

Invalid Closed 0 V Closed 0 V Closed 0 V

The Transmission Fluid Pressure (TFP) manual

valve position switch is a set of five pressure

switches on the control valve body that sense

whether fluid pressure is present in five different

valve body passages. The combination of which

switches are open and closed is used by the PCM

in order to determine actual m anual valve position.

The TFP manual valve position switch, however,

cannot distinguish between PARK and NEUTRAL

because the monitored valve body pressures are

identical in both cases.

The switch es are wir ed to provide thr ee signal lines

that are monitored by the PCM. These inputs are

used to help co ntrol line press ure, tor que converter

clutch apply and shift solenoid valve operation.

Voltage at each of the signal lines is either zero or

12 volts.

In order to monitor the TFP manual valve position

switch operation, the PCM compares the actual

voltage combination of the switches to a TFP

com bination tab le stored in its mem ory. If the PCM

sees one of two illegal voltage combinations, a

DTC P1810 will result. A DTC P1810 indicates a

short circuit condition in either the range signal A or

the ra nge signal C circuits.

The TFP manual valve position switch signal

voltage can be measured from each pin-to-ground

and compared to the combination table. On the

automatic transmission wiring harness assembly,

pin N is rang e sig nal A, pin R is range signal B, and

pin P is range signal C. With th e A/T wiring harness

assembly connected and the engine running, a

voltage measurement of these three lines will

indicate a high reading (near 12 volts) when a

circ uit is open, and a low r eading (zero volt s) when

the c ircuit is switched to ground.

8889

The transm issio n fluid tem perature (TFT ) s ensor is

part of the TFP manual valve position switch

assembly.

VEHICLE SPEED SENSOR

IMPORTANT: The sensor resistance is model

dependent and varies with speed from a minimum

of 0.5 volts AC at 100 RPM to mor e than 1 00 volts

AC at 8000 RPM.

The vehicle speed sensor (or transmission output

speed sensor) controls shift points and calculates

the TCC slip. The speed sens or contains a coil that

gives off a continuous magnetic field. A rotor

rotates past the sensor and the rotor teeth break

the m agnetic field. Each break in the field sends a

pulse to the VSSB (Vehicle Speed Sensor Buffer).

The VSSB sends two signals to the PCM. T he first

is a 2002 pulse per mile (PPM) signal that is used

by the engine. The second is the

transmission/transfer case 40 pulse per revolution

(PPR) signal that is used in order to control the

transmission.

The vehicle speed sensor is located on the

transmission extension housing. Trans Output

Speed = Transfer Case Speed.

DTC P0502 will set if a fault exists in the vehicle

speed sensor circuit 40 PPR line.

62801

AUTOMATIC TRANSMISSION FLUID TEMPERAT URE SENSOR

The Automatic Transmission Fluid Temperature

(TF T ) s ens or is pa rt o f th e Auto m at ic T r ansmis sion

Fluid Pressure (TFP) manual valve position switch

assembly. This sensor helps control torque

converter clutch apply and shift quality. The TFT

sensor is a resistor, or thermistor, which changes

value based on temperature. At low temperatures

the r esistance is high, and at high temperatu r es the

resistance is low.

The PCM sends a 5 volt signal to the TFT sensor

and the PCM measures the voltage drop in the

circuit. You will measure a high voltage when the

transmission is cold and a low voltage when the

transmission is hot. Refer to the Temperature vs

Resistance table in Section 6C3-4 Specifications

of this Service Information CD.

If th e TFT sensor cir cuit has a f ault, DT C P0712 or

P0713 is set. A DTC P0712 ind icates a sho rt circ uit

condition, while a DTC P0713 indicates an open

circuit condition. DTC P0218 is set if the

transm ission is oper ating at a high tem peratur e for

a period of time.

ELECTRICA L CONNECTOR

The transmission electrical connector is an important

part of the transmission operating system. Any

interference with the electrical connection can cause

the transmission to set Diagnostic Trouble Codes

(DTCs) or affect proper operation.

The following items can affect the electrical

connection:

• Bent pins in the connector from rough handling

during co nnection and disconnection.

• Wires backing away from the pins or coming

uncrimped (in either the internal or the external

wiring har ness) .

• Dirt contamination entering the connector when

disconnected.

• Pins in the internal wiring conne ctor back ing out of

the connector or pushed out of the connector

during reconnec tion.

• Excessive transmission fluid leaking into the

connector, wicking up into the external wiring

harness and degr ading the wire insulation.

• Moisture intrusion in the connector.

• Low pin retention in the external connector from

excessive connection and disconnection of the

wiring connector assembly.

• Pin corrosion from cont amination.

• Damaged connector assembly.

13265

Remember the following points:

• In or der to r em ove the co nnector , squee ze the two

tabs toward ea ch other and pull st raight up without

pulling by the wires.

• Limit twisting or wiggling the connector during

removal. Bent pins can occur.

• Do not pry the connector off with a screwdriver or

other tool.

• Visually inspect the seals to ensure that they are

not damaged du ring handling.

• In order to reinstall the external wiring connector,

first align the pins by lining up the arrows on each

half of the connector. Push the connector straight

down into the transmission without twisting or

angling the m ating parts.

• The connector should click into place with a

positive feel and/o r noise.

IMPORTANT: Whenever the transmission external

wiring connector is disconnected from the internal

harness and the engine is operating, DTCs will set.

Clear these DTCs after reconnecting the external

connector.

1.14 ABBREVIATIONS AND GLOSSARY OF TERMS

Abbreviations used in this Service Information CD are listed below in alphabetical order with an explanation of the

abbreviation.

POWERTRAIN MANAGEMENT

AC - ALTERNATING CURRENT - A current whose polarity is constantly chang ing between positive and negative.

A/C - AIR CONDITIONING

A/F - AIR/FUEL (A/F RATIO)

AN ALOG SIGNAL - An electrical signal that varies in voltage within a given param eter.

BAROMETRIC PRESSURE - Atmospheric pr essure. May be called BARO, or barometric absolute pressure.

BATTERY - Stores chemical energy and converts the chemical energy into electrical energy. This provides DC

current for the vehicle’s electrical systems.

CAT. CONV - CATALYTIC CONVERTER - A muffler-shaped device fitted in the exhaust system, between the

engine and the m uf fler . The purpo se of the cat alytic con verte r is to c hem ically conver t eng ine pro ducing gases into

environmentally safe gases. HC, CO, and NOx emitted by the engine, are converted to water vapour, carbon

dioxide, and nitrogen.

CHECK POWERTRAIN LA MP (CPL) - A W arning indic ator loc ated on the instr ument panel, and controlled by the

PCM. The lamp is illuminated by the PCM when it detects a fault in the engine management system, or when the

ignition is ON with the engine not runnin g (bulb che ck).

CKT - CIRCUIT

CLOSED LOOP - A fuel cont rol m ode of ope ration that us es the signal f rom the ex haus t oxygen sens or, in order to

control the air/fuel ratio pr ecisely at a 14.7 to 1 ratio. This allows maxi mum efficienc y of the catalytic converter.

CO - CARBON MONOXIDE - One of the pollutants found in the engine exhaust.

DIAGNOSTIC TROUBLE CODE - The PC M can det ect f aults in t he engine mana geme nt system . If a fault occur s,

the PCM m ay turn on the Ch eck Power train Lam p (CPL) and a four digit code num ber will set. A diagnos tic trouble

code can be read with the Tech 2 scan tool. This DTC will indicate the area of the fault.

DIAGNOSTIC TEST ENABLE TERMINAL - A terminal in the Data Link Connector(DLC) that is earthed to get a

Diagnos tic Tr ouble Code.

DIGITAL SIGNAL - An electrical signal t hat is either ON or OFF .

DLC - DATA LINK CONNECTOR - Used at the assembly plant to evaluate the engine management system. For

service to flash the Check Powertrain Lamp (CPL), use of Tech 2 scan tool and performing other system checks.

DLC DATA STREAM - An output from the PCM, initiated by the Tech 2 scan tool. This output is a digital signal,

used by assembly plant test equipment and the Tech 2 scan tool. This signal is transmitted from the PCM to the

Dat a Link Connector(DLC).

DMM (10 Meg Ohm) - MULTIMETER - A mult ipurpos e m eter t hat ha s cap ability of m eas uring Voltag e, Am ps , and

Ohms.

DRIVER - An elect r onic device, usua lly a power transistor, that op erates like an electr ical switch turning a circ uit ON

and OFF.

DUTY CYCLE - The tim e, in perce ntage, that a circuit is ON versus OF F .

FIELD SERVICE MODE - A PCM mode of operation that is used during service. It is operational when the engine is

running and the DLC diagnostic te st enable ter minal is earthe d.

ENGINE COO LAN T TEM PERATUR E (ECT ) SENSOR - A sens or that sense s the engine coo lant temp erature and

sends that information to the powertrain control module.

EECS - EVAPORATIVE EM ISSIONS CONT ROL SYST EM - Used t o prevent petrol vapo urs from the fuel tank from

enter ing into the atmosphere. The vap ours are stor ed in a canister, located under th e vehicle. The caniste r contains

an act ivat ed char coal element. The petrol vapour s are pur ged fro m the caniste r into the manif old to be burned in the

engine.

EMI OR ELECT RICAL NO ISE - An unwanted sign al int erf er ing with ano th er ne ede d signal. Comm on ex ample s are

an electric razor's effect on a te levision, or AM rad io r eception while dr iving under high voltage power lines.

EPROM - ERASABLE PROGRAMMABLE READ ONLY MEMORY - Type of Read Only Memory (ROM) that can

be erased with ultra vio let light and rep rogrammed.

ESD - ELECTROSTATIC DISCHARGE - The discharge of static electricity, which has built up on an insulated

material.

EEPROM - ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY - T ype of rea d o nly memo ry

(RO M) th at c an be electr ically program m ed, eras ed and re progra mme d using a sc an to ol. Also refe rre d to as F lash

Memory.

FIELD SERVICE MODE - A PCM mode of operation that is used during service. The field service mode is

operat ional when the engine is r unning and the DLC diagnost ic test enable terminal is earthed.

FUSE - A thin metal strip which melts through when excessive current flows through it, creating an open circuit,

protecting a circuit from damage.

HC - HYDROCARBONS (HC) - Any unburnt fuel leaving th e engine fr om inco mplet e combustion.

IAC VALVE - IDLE AIR CONTROL VALVE - Installed on the throttle body unit and controlled by the PCM to

regulate idle air flow, and thus idle RPM.

IAT SENSOR - INTAKE AIR TEMPERATURE SENSOR - A sensor that enses intake manifold incoming air

temperature, and sends the information to the PCM.

IDEAL M IXTURE - The air/fuel ratio which pr ovides the best pe rform ance , while m aintaining max imum c onversion

of exhaust emissions, typically 14.7 to 1 on petr ol engines.

IGN - IGNITION

INPUTS - Information from sensors (MAF, TPS, etc.) and switches (A/C request, etc.) used by the PCM to

determine how to control its outputs.

INTERMITTENT - An electrical signal that occurs now and then; not continuously. In electrical circuits, refers to

occa sional open, short, or earth in a circuit.

IPC - INS TRU MENT PANEL CLUSTER

LOW - A voltage les s t han a s pec if ic t hr es hold. Ope rat es t he s ame as an e art h and m a y, or m ay not, be conn ect ed

to chassis earth.

MAF - MASS AIR FLOW SENSOR - A device tha t monitor s t he amount of air f low coming in th e eng ine intake. T he

MAF sens or sends a signal to the PC M.

N.C. - NORMALLY CLOSED - Switch contac ts that are closed, when they are in the normal operating position.

N.O. - NORMALLY OPEN - Switch contacts that are normally open when in the normal operating position.

NOx - NITROGEN OXIDE - One of the pollutants found in spark ignition engine exhaust. The are formed from

normal combustion and increase in severity with combustion temperatures.

OXYGEN SEN SOR - T he exh aust gas oxygen sens or is locat ed in the exhaus t m anif old. T he O2 s ensor mea sur es

the oxygen in the ex haust m anif old af ter the c om bust ion pr ocess . T he O2 sens or produce s a sm all elect rical signa l

based on the amount of oxygen in the exhaust gas.

OPEN LOOP - The PCM control of the fuel control system witho ut the use of the oxygen sensor information.

OUTPUT - Functions, typic ally include solenoids and relays, that are controlled by the PCM.

PIM - POWERT RAIN INT ERFACE MODU LE - The PI M acts as a com m unica tion tr anslator between the PCM and

other onboar d c ontrolle rs t hat use a dif fe rent serial data prot ocol. T he GEN III V8 PCM uses the new Class II serial

data t o c om mun icate, while o th er cont rolle rs on the vehic le ar e desig ned to tran smit seria l data via the convent iona l

Universal Asynchronous Receive Transmit (UART) protocol. Since these two types of serial data are not

compatible, a translator or PIM is required to tr ansm it data in either direct ion between the PCM and ot her controller.

PCM - POWERTRAIN CONTROL MODULE - A metal cased box containing electronic circuitry which electrically

monitors and controls the transmission system and emission systems on the engine management system. It also

turns ON the Ch eck Power train Lamp (C PL) when a malfunction occurs in the system.

PCV - POSITI VE CRANKCASE VENTIL ATI ON - Method of rebur ning crankcase f umes , ra ther than pass ing them

directly into the atmosphere.

PROM - PROGRAMMABLE READ ONLY MEMORY - An electronic term used to describe the engine calibration

unit. A plug-in memory unit that instr ucts the PCM how to operate for a particular vehicle.

PULSE WIDTH MODULATED (PWM) - A digital sign al turned O N and OF F for a p ercentage of available o n-plus-

off cycle tim e. A signal that is 30% ON and 70 % OFF would be c alled a 30% ON PWM signal.

QUAD DRIVER - A transistor in the PCM, capable of operating four separate outputs. Outputs can be either ON-

OFF or pulse width modulate d.

RAM - RA NDOM A CCESS MEMORY - Is the m icr oproce ssor s "s cratc h pad". T he proc esso r can write int o, or read

from t his mem ory as neede d. This mem ory is volatile and needs a constan t supply of volta ge to be retained. If the

voltage is lost or removed, this memory is lost.

SERIAL DATA - Serial data is a series of rapidly changing voltage signals pulsed from high to low. These signals

are typically 5 volts (UART), 7 volts (Class II), and 12 or 0 volts (high or low) and are transmitted through a wire

often referred to as the Serial Data Circuit.

SFI - SEQUENTIAL FUEL INJECTION - Method of inj ecting f uel into the eng ine. Places a fuel inje ctor at each inlet

port of a cylinder head, directly in front of the intake valve, mount ed in the intak e manifold.

SOLENOID - An electromagnetic coil which creates a magnetic field when current flows through it and causes a

plunger or ball to m ove.

SWITCH - Opens and closes circuits , thereb y controlling current flow.

TCC - TORQUE CONVERTER CLUTCH - A PCM c ont rolled sole noid in an aut om at ic tr ans miss ion which pos itively

couples the transmission input shaft to the engine.

TECH 2 SCAN TOOL - The Tech 2 scan tool is a hand held computer designed to aid in diagnosis and repair of

automotive systems with electronic controls/interfaces. The Tech 2 scan tool connects to the vehicle’s Data Link

Connector (DLC ).

TP SENSOR - THROTTLE POSITION - A sensor that sends a signal to the PCM. The PCM can determine from

this signal the current throttle position, and th e rate of throttle opening / closing.

VACUUM, M ANIFOLD - A vacuum source from below the thrott le plate.

VACUUM, PORTED - Vacuum source from a small port in the throttle body. With the throttle closed, there is no

vacuum, because the port is on the air c leaner side of the throttle blade, and is exposed to engine vacuum only after

the throttle is open.

VSS - VEHICLE SPEED SENSOR - A perm anen t m agnet type senso r which produ ces an AC voltag e which is sent

to the PCM to determine vehicle speed.

UART - UNIVERSAL ASYNCHRONOUS RECEIVE AND TRANSMIT - A method of communicating between

electr onic devices.WOT - WIDE OPE N TH ROTTLE - A throttle position opening greater than 80%.

AUTOMATIC TRANSMIS SION

AT - Automatic Transmission

BUMP - A sudden and forceful app ly of a clut ch or a band.

CHUGGLE - A bucking or jerking. This c ondition m ay be most noticeable when the converte r clutch is engaged. It is

sim ilar to the feel of towing a trailer.

DC - Direc t Current

DELAYED - A condition wher e a shift is expected but does not occur fo r a perio d of time. This could be descr ibed

as a clutch or band engagement that does not occur as quickly as expected during a part or wide open throttle

application, or during manual downshifting to a lower range. This term is also defined as LATE or EXTENDED.

DOUBLE BUMP (DOUBLE FEEL) - T wo sudden and f orcef ul applications of a clutc h or a band when downshifting

during a zero throttle c oastdown.

DRIVE LINK NOI SE - A whine or gr owl that in creases or f ades with vehicle speed, and is m ost not iceable u nder a

light throttle acceleration. It may also be noticeable in PARK or NEUTRAL operating ranges with the vehicle

stationary.

EARLY - A condition where the shift occurs before the vehicle has reached proper speed. This condition tends to

labour t he engine aft er the upsh ift.

END BUMP - A firm er feel at the end of a shift than at the start of the shift. This is also defined as END FEEL or

SLIP BUMP.

ENGINE BR AKING - A con dition where the engine is used to slow the vehicle on clos ed throttle or low gear.

ETC - Electronic Traction Control

FINAL DRIVE NOISE - A hum r elated to vehicle sp eed which is most notice able under a light throttle acceleration.

FIRM - A notice ably quick apply of a clu tch or band that is co nsidered nor mal with a m edium to heavy throttle. T his

apply should not be confused with HAR SH or ROUGH.

FLARE - A quic k increase in engine RPM along with a mom entary loss o f torque. This most generally occur s during

a shift . This condition is also defined as SLIPPING.

FULL THROTTLE DETENT DOWNSHIFT - A quick apply of the accelerator pedal to its full travel, forcing a

downshift.

HARSH (ROUGH) - A more noticeable apply of a clutch or band than FIRM. This condition is considered

undesirable at any thrott le position.

HEAVY THROTTLE - Approximately 3/4 of accelerator pedal travel (75% throttle position).

HUNTING - A repeating quick series of upshifts and downshifts that causes a noticeable change in engine RPM,

such as a 4- 3-4 shif t pattern . This c ondition is also defined as BUSYNESS.

INI TIAL FEEL - A distinctly firmer feel at the start of a shift than at the finish of the shift.

LATE - A shift that occurs when the engine RPM is higher than no rmal for a given amou nt of thr ottle.

LIGHT THROTTLE - Approxim ately 1/4 of accelerator pedal travel (25% throttle position).

MEDIUM THROTTLE - Approximately 1/2 of accelerator pedal travel (50% throttle position).

MI NIMUM THR O TTL E - The least amount of throttle opening required for an upshift.

OBD - On Board Diag nostic

OSS - Output (Shaft) Speed Sensor

PC - Pressu r e Control

PLANETARY GEAR NOISE - A whine rela ted to vehic le spee d, which is m ost noticea ble in FIRST ge ar, SECO ND

gear, FOURTH gear or REVERSE. The condition m ay become less noticeable, or go away, after an upshift.

PM - Per manent Magnet

PUMP NOISE - A high pitched whine that increases in intensity with engine RPM. This condition may also be

noticeable in all operating ranges with the vehicle stationary or moving.

RPM - Revolutions Per Minute

SHIFT CONDITION DEFINITIONS

SHUDDER - A repea ting jer king cond ition sim ilar to CH UGGLE but m ore s evere and rapid . This co ndition m ay be

m ost notic eable during certain ranges of vehic l e speed.

SLIPPING - A noticeable incre ase in engine RPM withou t a vehicle speed incr ease. A slip usually occurs during or

after initial clut ch or band app ly.

SOFT - A slow, almost unnotice able clutch or band apply with very little shift feel.

SS - Shift Solenoid

SURGE - A repeating engine related conditio n of acceleration and deceleration that is less int ense than CHUGGLE.

TAP - Transmissio n Adaptive Pressure

TFP - Transm ission Fluid Pres sure

TFT - Transmission Fl uid Tempera ture

TIE-UP - A con dition wher e two opposing clutch an d/or ban ds ar e attem pt ing to apply at the sam e tim e caus ing the

engine to labour with a noticeable loss of engine RPM.

TORQUE CONVERTER NOISE - A whine usually noticed when a vehicle is stopped, and the transmission is in

DRIVE or REVERSE. The noise will incr ease with engine RPM.

TV - Throttl e V al v e

WIDE OPEN THROTTLE (WOT) - Full travel of the accelerat or pedal (100% throt tle position).

ZERO THROTTLE COASTDOWN - A full release of the accelerator pedal while the vehicle is in motion and in

Drive range.