SECTION 6C1-1 GENERAL INFORMATION

CAUTION

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

will consist of either seat belt pre-ten sioners and a driv er’s side air bag, or seat belt

pre-tensioners and a driver’s and front passenger’s side air bags. Refer to

CAUTIONS, Section 12M, before performing any service operation on or around SRS

components, the steering mechanism or wiring. Failure to follow the CAUTIONS

could result in SRS deployment, resulting in possible personal injury or

unnecessary SRS system repairs.

CAUTION

This vehicle may be equipped with LPG (Liquefied Petroleum Gas). In the interests

of safety, the LPG fuel system should be isolated by turning 'OFF' the manual

service valve and then draining the LPG service lines, before any service work is

carried out on the vehicle. Refer to the LPG leaflet included with the Owner's

Handbook for details or LPG Section 2 for more specific servicing information.

1. GENERAL DESCRIPTI ON

The engines used in this vehicle uses a Powertrain Control Module (PCM) with both an automatic transmission and a

manual transmission to control exhaust emissions while maintaining excellent driveability and fuel economy. The PCM

maintains a desired air/fuel ratio of precisely 14.7 to 1 by monitoring electrical signals from dual oxygen sensors

mounted in the exhaust stream and optimising the amount of fuel flow from the injectors. This method of "feed back"

fuel control is called CLOSED LOOP.

In addition to fuel control, the PCM also controls ignition dwell and timing, idle speed, EGR, electric engine cooling fan,

electric fuel pump, instrument panel "Check Powertrain" lamp and on vehicles so equipped, the A/C compressor clutch.

The PCM also controls the automatic transmission functions. The PCM also interfaces through the serial data line with

other vehicle control or information modules, such as the trip computer, Body Control Module (BCM), ABS/ETC module,

ECC module, SRS module, and theft deterrent system. Figures 6C1-1-1 through 6C1-1-4 contain a list of the various

operating conditions sensed by the PCM on the left, and the various systems controlled on the right. Details of basic

operation, diagnosis, and service are covered in this and other relevent Sections.

The PCM has a built-in diagnostic system that recognises and identifies possible operational problems and alerts the

driver by illuminating the "Check Powertrain" lamp/Malfunction Indicator Lamp (MIL) on the instrument panel. If the

lamp comes "ON" while driving, it does not mean that the engine should be stopped immediately, but the cause of the

lamp coming "ON" should be checked as soon as is reasonably possible. The PCM has built-in backup systems that in

all but the most severe failures will allow the vehicle to operate in a near normal manner until repairs can be made.

Below the instrument panel to the left of the steering column is a Data Link Connector (DLC) which is used by the

assembly plant for a computer "check-out" of the system. This connector is used in service along with a scan tool to

help diagnose the system. Refer to Section 6C1-2, DIAGNOSIS for further details.

The locations of the Engine Management System (EMS) components of the system are shown in the following

Figures 6C1-1-5 through 6C1-1-13.

For the Transmission Management System components and their locations, refer to Figure 6C1-1-60 in this Section.

Techline

Figure 6C1-1-1 Non-Supercharged Engine Powertrain Control Module Systems

Figure 6C1-1-2 Supercharged Engine Powertrain Control Module Systems

Figure 6C1-1-3 Non-Supercharged Engine Powertrain Control Module Systems

Figure 6C1-1-4 Supercharged Engine Powertrain Control Module Systems

Figure 6C1-1-5 Non-Supercharged Engine Compartment Component Locations

Figure 6C1-1-6 Supercharged Engine Compartment Component Locations

Figure 6C1-1-7 Engine Compartment Relay Locations

Figure 6C1-1-8 Non-Supercharged Engine Component Locations

Figure 6C1-1-9 Supercharged Engine Component Locations

Figure 6C1-1-10 Non-Supercharged Engine Component Locations

Figure 6C1-1-11-Supercharged Engine Component Locations

Figure 6C1-1-12 Non-Supercharged Engine Component Locations

Figure 6C1-1-13 Supercharged Engine Component Locations

1.1 POWERTRAIN CONTROL MODULE (PCM)

POWERTRAIN CONTROL MODULE (PCM)

The Powertrain Control Module (PCM), located

behind the front left hand cowl trim panel, and is

the control center of the fuel injection and

transmission management systems. It constantly

monitors information from various sensors, and

controls the systems that affect exhaust emissions

and vehicle performance. The PCM performs the

diagnostic function of the system. It can recognise

operational problems, alert the driver through a

Malfunction Indicator Lamp (MIL) "Check

Powertrain" lamp and store a diagnostic code(s)

that will identify problem areas to aid the technician

in making repairs. Refer to Section 6C1-2

DIAGNOSIS for more information on using the

diagnostic functions of the PCM.

The PCM s upplies either a buf fer ed 5 or 12 volts to

power various sensors or switches. This is done

through resistance's in the PCM which are so high

in value that a test light will not light when

connected to the circuit. In some cases, even an

ordinary voltmeter will not give an ac curate reading

because the meter's internal resistance is too low.

Figure 6C1-1-14 Powertrain Control Module Location

A 10 Megaohm input impedance digital voltmeter is

required to assure accurate voltage readings.

The PCM controls output circuits such as the

injectors, IAC, and various relays, etc. by

controlling the earth circuit through transistors or a

device called a "Q uad-Driver" m odule (QDM) in the

PCM. The two exceptions to this are the fuel pump

relay control circuit and the autom atic transmission

Pressure Control Solenoid (PCS). The fuel pump

relay is the only PCM controlled circuit where the

PCM controls the +12 volts sent to the coil of the

relay. The earth side of the fuel pump relay coil is

connected to engine earth. The PCM supplies

current to the PCS and m onitors how m uch curr ent

returns to the PCM on a separate terminal.

PCM SECURITY LINK

Once the PCM and or BCM have been replaced,

the new PCM and or BCM must be security linked

to each other. If this procedure is not performed,

the vehicle will not crank.

There are two different types of procedures that

may be perform ed to ac com plish this tas k. Ref er to

Section 6C1-3 SERVICE OPERATIONS for this

procedure.

Figure 6C1-1-15 PCM Mounting

PROM

To allow one model of PCM to be used for many

diff erent vehicles, a device called a PROM is used.

The PROM is located inside the PCM and has

information on the vehicle's weight, engine,

transmission, axle ratio and several other factors.

While one PCM part number m ay be used by m any

different vehicles, a PROM is specific. For this

reason, it is very important to chec k the latest par ts

catalogue and Technical Information Bulletins for

the correct part number when replacing a PROM.

A replacement PCM (called a controller) is

supplied without a PROM. The PROM from the old

PCM must be carefully removed and installed in the

new PCM. For details refer Section 6C1-3

SERVICE OPERATIONS.

Figure 6C1-1-16 PROM Location

PCM MEMORY FUNCTIONS

There ar e three types of mem ory storage within the

PCM: RAM, EPROM and EEPROM.

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 voltage to be retained. If the voltage is

lost, the memory is lost.

EPROM

Erasable Programmable Read Only Memory

(EPROM) is the portion of the PCM which means

that the program can be erased. This is also the

portion of the PCM that contains software and the

different engine and transmission calibration

information that is specific to year, model and

emis sions. T his m emor y is erased by exposing it to

high intensity ultra violet radiation for several

minutes.

The service Programmable Read Only Memory

(PROM) which is used by technicians in the field to

update calibrations in the PCM is actually an

EPROM. T he service PROM is r emovable fr om the

PCM. The PROM should be retained with the

vehicle following PCM replacement.

EEPROM

Electronically Erasable Programmable Read Only

Memory (EEPROM) is the portion of the PCM that

means the program can only be erased

electronically. This type of memory cannot be

erased by disconnecting the vehicle's battery. The

only way to erase this type of memory is by a

special electronic tool, such as the Tech 2 scan

tool. This type of memory is used to store the

Diagnostic Trouble Codes (DTC). DTC history data

is stored in EEPROM and will be saved even after

the vehicle's battery has been disconnected. For

this reason, the only way that the DTC history data

can be cleared is with the Tech 2 scan tool.

1.2 ENGINE INFORMATION SENSORS AND SIGNALS

CAMSHAFT POSITION SENSOR

The camshaft position sensor is located in the

engine front cover, behind and below the water

pump, near the camshaft sprocket.

As the camshaf t spr ock et turns, a m agnet m ounted

on it activates the Hall Ef f ec t s witch in the c ams haf t

position sensor. When the Hall Effect switch is

activated, it earth's the signal line to the DIS

module, pulling the camshaft position signal line's

applied voltage low. This is interpreted as a

camshaft position signal (Synchronisation Pulse).

Because of the way the signal is created by the

camshaft position sensor, the signal circuit is

always either at a high or low voltage (square wave

signal).

While the camshaft sprocket continues to turn, the

Hall Eff ect switch turns "OFF" as the m agnetic f ield

passes the camshaft position sensor, resulting in

one signal each time the camshaft makes one

revolution.

The camshaft position signal, which actually

represents camshaft position due to the sensor's

mounting location, is used by the PCM to properly

time its sequential fuel injection operation.

Figure 6C1-1-17 Camshaft Position Sensor

Figure 6C1-1-18 Camshaft And Crankshaft Position Sensor Locations

CAMSHAFT POSITION SIGNAL

The PCM uses the camshaft position signal to

determine the position of the No. 1 piston on its

power stroke. This signal is used by the PCM to

calculate sequential fuel injection operation. If the

camshaft position signal is lost while the engine is

running, the fuel injection mode will be based on

the last fuel injection pulse, and the engine will

continue to run. The engine can be restarted and

will run in the synchronous (all six inj ectors inject at

once) mode as long as the fault is present.

When the camshaft position signal is not received

by the PCM, a DTC 48 will be set. An intermittent

camshaft position signal will set a DTC 49. If either

of these DTC's are set, the fuel system will not be

in sequential fuel injection mode.

Figure 6C1-1-19 Camshaft Position Signal

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

The Engine Coolant Temperature (ECT) sensor is a

thermistor (a resistor that changes value based on

temperature) mounted in the engine coolant stream

and is specifically for the PCM. A different sensor is

used for instrument panel functions. Low coolant

engine temperature produces a high sensor

resistanc e (28,939 ohms at - 20 degrees C) while high

engine coolant temperature causes low sensor

resistance (180 ohms at 100 degrees C).

Figure 6C1-1-20 ECT Sensor

The location of the sensor for the Supercharged

application is at the rear of the engine. Both sensor

application are located near the thermostat housing.

Figure 6C1-1-21 ECT Sensor Location (Supercharged

Engine)

The Engine Coolant Temperature location on the

Non-Supercharged application is at the front of the

engine

Figure 6C1-1-22-A ECT Sensor Location (Non-

Supercharged Engine)

The PCM:

1. Supplies a 5 volt signal voltage to the sensor

through a resistor in the PCM, and

2. Monitors the circuit voltage, which will change

when connected to the sensor.

The circuit voltage will vary depending on the

resistance of the engine coolant temperature sensor.

The circuit voltage will be close to the 5 volt level

when the sensor is cold, and will decrease as the

sensor warms. Engine coolant temperature affects

most systems controlled by the PCM.

A failure in the engine coolant temperature sensor

circuit should set either a Diagnostic Trouble Code

(DTC) 14 or DTC 15. An intermittent open or a short

failure s hould set DTC 16. T he PCM supplies a 5 volt

signal to the engine coolant temperature sensor

through one of two resistors in the PCM. When the

engine coolant is cold the PCM will operate on one

resistor then switch over to another resistor at

approximately 50 degrees C. The circuit voltage will

change at this time but the Tech 2 scan tool will still

read the correct temperature value and will not

suddenly jump. A f ailure in one of these two resistor s

will set DTC 17.

Figure 6C1-1-23 ECT Temperature vs Voltage

Figure 6C1-1-24 ECT Sensor Circuit

EXHAUST GAS OXYGEN SENSOR

The exhaust gas oxygen sensors are the key to

closed-loop f uel contr ol. The PCM us es inform ation

from the oxygen sensors to precisely fine-tune its

fuel injector pulse width calculations, based on the

unused, "left-over" oxygen content in the exhaust.

The Non-Supercharged V6 engine use two

unheated oxygen sensors, one oxygen sensor is

located in each exhaust pipe. This is done so that

the PCM can better control the engine's fuelling

requirements. By monitoring the exhaust oxygen

content of each bank of cylinders, the PCM can

better control the fuel injector pulse width to the

individual fuel injectors on each bank.

The Supercharged V6 engine uses two heated

oxygen sensors. These heated oxygen sensors

have a internal heater element that is used to heat

the Zirconia element faster inside the sensors,

thereby decreasing the amount of time the fuel

control system can begin running in closed loop

fuel control.

Both type of oxygen sensors have a zirconia

element that, when heated to temperatures above

360 degrees C, produce voltages based on the

amount of oxygen content surrounding the tip, as

compared to oxygen in the atmosphere.

Figure 6C1-1-25 Two Wire Oxygen Sensor

The sensor is mounted in the exhaus t pipe with the

sensing portion exposed to the exhaust gas

stream. When the sensor has reached an operating

temper ature of m ore than 360 degrees C, it ac ts as

a voltage generator, producing a rapidly changing

voltage of between 10 - 1000 millivolts. This voltage

output is dependent upon the oxygen content in the

exhaust gas, as compared to the sensor's

atmospheric oxygen reference cavity. This

reference cavity is exposed to the atmosphere

through the air that passes between the wire

strands and insulation.

When the sensor is cold, it produces either no

voltage, or an unusable, slowly changing one. Also

when cold, its internal electrical resistance is

extremely high - many million ohms. The PCM

always supplies a steady 450 millivolt, very low

current called "bias" voltage to the oxygen sensor

circuit. W hen the sensor is cold and not producing

any voltage, the PCM "detects" only this steady

bias voltage. As the sensor begins heating, its

internal resistance decreases and it begins

producing a rapidly changing voltage that will

overshadow the PCM's supplied steady bias

voltage.

Figure 6C1-1-26 Four Wire Heated Oxygen Sensor

When the PCM "detects" the changing voltage, it

knows the oxygen sensor is hot and its output

voltage can be used for the "fine-tuning" the fuel

injector pulse width. T he PCM monitors the oxygen

sensor's "changing voltage" for going above and

below a mid-range voltage band (approximately

300 - 600 millivolts), to help dec ide when to operate

in the closed-loop mode. (refer "READY TEST,"

Figure 6C1-1-29.)

W hen the fuel system is correctly operating in the

closed-loop mode, the oxygen sensor voltage

output is rapidly changing several times per

second, going above and below a rich/lean band.

The PCM monitors the changing voltage, and

decides the needed fuel mixture correction. (refer

"NORMAL, CLOSED-LOOP OPERATION,"

Figure 6C1-29).

An open sensor signal circuit or earth circuit, or a

defective, contaminated, or cold sensor could

cause the voltage to stay within a 350-550 millivolt

band too long, keeping the fuel control system in

open-loop and setting a DTC 13 or DTC 63. (refer

"DTC 13 or DTC 63", Figure 6C1-28).

Figure 6C1-1-27 Oxygen Sensor Zirconia Element

If the PCM monitors a low voltage for too long

(indicating a "lean" exhaust), a DTC 44 or DTC 64

will store in memory. If the PCM monitors a high

oxygen sensor circuit voltage for too long

(indicating a "rich" exhaust), a DTC 45 or DTC 65

will store in m e mory (refer "DTC 44 or DTC 64" and

"DTC 45 or DTC 65", Figure 6C1-28).

RESPONSE TIME

Not only is it necessary for the oxygen sensor to

produce a voltage signal for rich or lean exhaust, it

is also important to respond quickly to changes.

The PCM senses the response times and displays

this on the Tech 2 scan tool as the "rich-lean

status" and as "cross counts" If the oxygen sensor

responds slowly, the customer may complain of

poor fuel economy, rough idle or lack of

performance. It may also set false PCM DTCs

because the PCM uses oxygen sensor voltages for

system checks.

OXYGEN SENSOR CONTAMINANTS

CARBON

Black carbon or soot deposits result from over-rich

air/fuel mixtures. However, carbon does not harm

an oxygen sensor. Deposits can be burned off in

the vehicle by running it at least part thr ottle for two

minutes.

SILICA

Certain RTV silicone gasket materials give off

vapour as they cure that may contaminate the

oxygen sensor. This contamination is usually

caused by the vapours being pulled from the PCV

system, into the combustion chamber and passed

on to the exhaust system. The sand like particles

from the RTV silica embed in the molecules of the

oxygen sensor element and plug up the surface.

With the outside of the oxygen sensor element not

able to sense all of the oxygen in the exhaust

system it results in "lazy" oxygen sensor response

and engine control. The oxygen sensor will have a

whitish appearance on the outside if it has been

contaminated.

There is also a possibility of silica contamination

caused by silicone in the fuel. Some oil companies

have used silic one to rais e the oc tane rating of their

fuel. Careless fuel handling practices with transport

containers can result in unacceptable

concentrations of silicone in the fuel at the pump.

There is also a possibility of silica contamination

caused by silicon in lubricants used to install

vacuum hoses on fittings. Do not use silicone

sealers on gaskets or exhaust joints.

LEAD

Lead glazing of the sensors can be introduced

when regular, or leaded fuel is burned. Fuel

containing large amounts of methanol will also

result in lead contamination.

The methanol dissolves the terne coating of the fuel

tank, which introduces lead into the fuel system,

and into the exhaust after combustion. It is difficult

to detect lead contamination by visual inspection.

OTHER SUBSTANCES

Oil deposits will ultimately prevent oxygen sensor

operation. The sensor will have a dark brown

appearance. Causes of high oil consumption

should be checked.

The additives in ethylene glycol can also affect

oxygen sensor performance. This produces a

whitish appearance. If antif reeze enters the ex haus t

system, you will likely encounter other, more

obvious, symptoms of cooling system trouble. If for

example the engine had a head gasket failure

where coolant did enter the combustion chamber it

would be a good idea to check the oxygen sensor

operation after the head gasket was repaired.

MULTIPLE FAILURES

Leaded fuel, silica contamination from uncured,

low-grade (unapproved) RTV sealant, and high oil

consumption are possible.

A problem in the oxygen sensor circuit or fuel

system should set a DTC 13 or DTC 63 (open

circuit), DTC 44 or DTC 64 (lean indication), or

DTC 45 or DTC 65 (rich indication). Refer to

applicable diagnostic chart if any of these DTCs

were stored in memory.

Figure 6C1-1-28 Oxygen Sensor Voltage Curves

Figure 6C1-1-29 Normal Oxygen Sensor Voltages, and Abnormal Trends

Figure 6C1-1-30 Two Wire Oxygen Sensor Circuit

Figure 6C1-1-31 Four Wire Heated Oxygen Sensor Circuit

INTAKE AIR TEMPERATURE (IA T) SENSOR

The Intake Air Temperature (IAT) sensor is a

thermistor (a resistor that changes resistance with

changes in tem perature) mounted in an air cleaner

housing of the intake system. Low intake air

temper atur e produces high res istanc e in the sens or

(100,866 ohm s at -40 degr ees C), while high intak e

air temperature causes low sensor resistance (78

ohms at 130 degrees C).

The PCM:

1. Supplies a 5 volt signal voltage to the sensor

through a resistor in the PCM, and

2. Monitors the intake air temperature circuit

voltage, which will change when connected to

the intake air temperature sensor.

The circuit voltage will vary depending on the

resistance of the IAT sensor. The voltage will be

close to the 5 volt level when the sensor is cold,

and will decrease as the sensor warms.

The input intake air temperature signal voltage is

used by the PCM to assist in calculating the fuel

injector pulse width.

A failure in the IAT sensor circuit should set either a

Diagnostic Trouble Code (DTC) 23 or DTC 25. An

intermittent failure in the IAT sensor circuit should

set DTC 26. Figure 6C1-1-32 IAT Sensor

Figure 6C1-1-33 IAT Sensor Location

Figure 6C1-1-34 IAT Sensor Circuit

MASS AIR FLOW (MAF) SENSOR

The Mass Air Flow (MAF) sensor used on these

engines utilises a heated element type of operation.

A heated element in the MAF is placed in the air

flow stream of the engine intake system. The

heating element is maintained at a constant

temperature differential above the air temperature.

The am ount of elec trical power r equired to m aintain

the heated element at the proper temperature is a

direct function of the mass flow rate of the air past

the heated element.

Figure 6C1-1-35 Mass Air Flow Sensor

Figure 6C1-1-36 MAF Sensor Location

Non-Supercharged Engine

Three sensing elements are used in this system.

One senses ambient air temperature and uses two

calibratable resistors to establish a voltage that is

always a function of ambient temperature. This

ambient sensor is mounted in the lower half of the

sensor housing. The other two sensing elements

are heated to a predetermined temperature that is

significantly above ambient air temperature. The

two heated elements are connected electrically in

parallel and mounted directly in the air flow stream

of the sensor housing. O ne sensor is in the top and

one 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 air passes over the heated elements during

engine operation they begin to cool. By measuring

the amount of electrical power required to m aintain

the heated elements at the predetermined

temperature above ambient temperature the mass

air flow rate can be determined.

Once the mass air flow sensor has developed an

internal signal related to the mass air flow rate, it

must send this information to the PCM. In order to

preserve the accuracy and resolution of the small

voltage signal in the mass air flow sensor, it is

converted to a frequency signal by a voltage

oscillator and sent to the PCM.

Figure 6C1-1-37 Sensing Elements

Figure 6C1-1-38 MAF Sensor Simplified Schematic

The signal that is sent from the mass air flow

sensor is sent in the form of a frequency output. A

large quantity of air passing through the sensor

(such as when accelerating) will be indicated as a

high frequency output. A small quantity of air

passing through the sensor will be indicated as a

low frequency output (such as when decelerating or

at idle). The T ech 2 scan tool displays MAF sens or

information in frequency, and in grams per second

and calculated in mg per cylinder. At idle the

readings should be low and increase with engine

RPM.

As the PCM receives this f requency signal from the

Mass Air Flow sensor, it searches its pre-

program med tables of inform ation to determine the

pulse width of the fuel injectors required to match

the Mass Air Flow signal.

If a problem occurs in the Mass Air Flow sensor

circuit, after a period of time, the PCM will store a

DTC in its memory. The PCM will turn "ON" the

"Check Powertrain" lamp Malfunction indicator

Lamp (MIL) indicating there is a problem. If this

occurs, the PCM will calculate a "substitute" Mass

Air Flow signal based on engine speed and Throttle

Position (TP) sensor signal.

No field service adjustment is necessary or

possible with this Mass Air Flow sensor.

A failure in the Mass Air Flow sensor circuit should

set a DTC 32. Remember, this code indicates a

failure in the circuit, so pr oper use of the diagnos tic

chart will lead to either repairing a wiring problem or

replacing the MAF Sensor, to properly repair a

problem.

Figure 6C1-1-39 Mass Air Flow Sensor Identification

Figure 6C1-1-40 MAF Sensor Circuit

THROTTLE POSITION (TP) SENSOR

The Throttle Position (TP) sensor is connected to

the throttle shaft on the throttle body unit. It is a

potentiometer with one end connected to 5 volts

from the PCM and the other end to PCM earth. A

third wire connects from a sliding contact in the TP

sensor to the PCM allowing the PCM to measure

the voltage from the TP sensor. As the throttle is

moved ( acceler ator pedal m oved), the output of the

TP sensor changes. At a closed throttle position,

the output of the TP sensor is below 1.25V. As the

throttle valve opens, the output increases so that, at

wide-open throttle (WOT), the output voltage

should be about 4 volts.

By monitoring the output voltage from the TP

sensor, the PCM can determ ine fuel delivery based

on throttle valve angle (driver demand). A broken or

loose TP sensor can cause intermittent bursts of

fuel from the injectors, and an unstable idle,

because the PCM interprets the throttle is moving.

Figure 6C1-1-41 TP Sensor

The TP sensor is not adjustable and there is not a

set value for voltage at closed throttle because the

actual voltage at closed throttle can vary from

vehicle to vehicle due to tolerances. The PCM has

a special progr am built into it that can adjus t for the

tolerances in the T P sensor voltage reading at idle.

The PCM uses the reading at clos ed throttle idle for

the zero reading (0% throttle) so no adjustment is

necessary. Even if the TP sensor voltage reading

was to be change by: tampering, throttle body

coking, sticking cable or any other reason, the TP

sensor will still be 0%. The PCM will learn what the

closed throttle value is every time the throttle

comes back to closed throttle. The new closed

throttle value will be used by the PCM and no

driveability complaint will be present because the

PCM learned a new setting.

A failure in the TP sensor circuit problem will set

DTC 21 or DTC 22. If the internal spring in the TP

sensor should fail, the T P sensor will be stuck high.

A sticking TP sensor should set DTC 19. Figure 6C1-1-42 TP Sensor - Typical

Figure 6C1-1-43 TP Sensor Location

Figure 6C1-1-44 TP Sensor Circuit

EXHAUST GAS RECIRCULATION (EGR) SYSTEM

NON-SUPERCHARGED ENGINE APPLICATION ONLY

PURPOSE

The Exhaust Gas Recirculation (EGR) system is

used to lower Oxides of Nitrogen (NOx) emission

levels caused by high combustion temperatures. It

does this by decreasing combustion temperature.

The main element of the system is the linear EGR

valve. The EGR valve feeds small amounts of

exhaust gas back into the compression chamber.

With the air/fuel mixture thus diluted, combustion

temperatures are reduced.

Figure 6C1-1-45 Linear EGR Valve Location

OPERATION

The linear EGR valve is designed to accurately

supply EGR to an engine independent of intake

manifold vacuum. The valve controls EGR flow

from the exhaust to the intake m anifold through an

orifice with a PCM controlled pintle. During

operation, the PCM controls pintle position by

monitoring the pintle position feedback signal. The

feedback signal can be monitored with a scan tool

as "EGR POS. FEEDBACK". "EGR POS.

FEEDBACK" should always be near the

commanded EGR position ("EGR POS.

COMMANDED"). If a problem with the EGR system

will not allow the PCM to control pintle position

properly, DTC 29 should set. The PCM also tests

for EGR flow; if incorrect flow is detected, DTC 18

should set. If DTC 29 and/or DTC 18 are

encountered, refer to appropriate DTC chart in

section.

The Linear EGR valve is usually activated under

the following conditions:

• Warm engine operation

• Above idle engine speed

• Vehicle not in Park or Neutral

• Fuel Control Is In Closed Loop Mode

LINEAR EGR CONTROL

The PCM monitors EGR feedback position and

adjust pintle position accordingly. The PCM uses

information from the following sensors to control

the pintle position:

• Engine Coolant Temperature (ECT) sensor.

• Mass Air Flow (MAF).

• Engine RPM.

RESULTS OF INCORRECT EGR SYSTEM

OPERATION

Too much EGR flow at idle, cruise, or cold

operation may cause any of the following conditions

to occur:

• Engine stalls after cold start.

• Engine stalls at idle after deceleration.

• Vehicle surge during cruise.

• Rough idle.

• Misfire.

Too little or no EGR flow may allow combustion

temperatures to get too high. This could cause:

• Spark knock (detonation).

• Engine overheating.

• High emissions.

• Poor fuel economy.

• DTC 18.

Figure 6C1-1-46 Linear EGR Valve Circuit

VEHICLE SPEED SENSOR (VSS)

The Vehicle Speed Sensor (VSS) is located on the

transm iss ion. Refer to Figure 6C1-1- 47 for the VSS

Location - Automatic Transmission and 6C1-1-48

for the VSS Location - Manual Transmission.

The VSS provides an indication of road speed to

the PCM. The sensor is mounted to the

transmission where it is gear driven by the

transmission output shaft. The sensor is an

electronic Hall effect switch that pulses to earth a

voltage signal com ing from the PCM. T hese pulses

occur 10 tim es per sensor revolution, and ar e used

by the speedometer for driver information.

The PCM also uses information from the VSS for

IAC valve operation and some of the engine fuelling

modes. If the PCM receives no pulses on the

vehicle speed sensor input while certain conditions

exist, a DTC 24 (Automatic Transmission) or DTC

94 (Manual Transmission) will be set.

Diagnostic Trouble Code (DTC) 24 or 94 will set if a

fault exis ts in the vehicle s peed sensor circ uit when

the vehicle is decelerated, and the VSS signal is

constant, or not pulsing. DTC 24 or 94 will set and

a default value will be substituted by the PCM. As

long as the fault r emains and the diagnostic trouble

code is set. If the fault is removed, normal

operation will resume after the next ignition cycle

Figure 6C1-1-47 VSS Location - Automatic Transmission

Figure 6C1-1-48 VSS Location - Manual Transmission

The vehicle speed sensor contains a coil that has

continuous magnetic field. A voltage signal is

induced in the vehicle speed s ens or by teeth on the

output shaft that rotate past the sensor and break

the magnetic field. Eac h break in the field s ends an

electrical pulse to the PCM. T his voltage output will

vary with transmission output shaft speed from a

minim um of 0.5 volts AC at 100 RPM to more than

100 volts AC at 8000 RPM with no load on the

circuit on the vehicle, with the engine at 4,000 RPM

in fourth gear the voltage will be approximately 10-

12 Volts AC.

The PCM uses speed information from this sensor

to determine the following:

• Vehicle speed.

• Control shift points (Auto Trans).

• Calculate transmission slip (Auto Trans).

• Engine fuelling modes.

Diagnostic Trouble Code (DTC) 24 or 94 will set if a

fault exists in the vehicle speed sensor circuit

indicating the vehicle is not moving. For the

automatic transmission, as the vehicle is

accelerated the PCM shifts the transmission to

second gear at approximately 50 km/h. If the

vehicle speed signal is still not present while in

second gear, DTC 24 is set, the transmission will

have maximum line pressure, 2 ND gear only and

have no TCC and a def ault value will be s ubs tituted

by the PCM.

Figure 6C1-1-49 VSS

Figure 6C1-1-50 VSS Circuit

A/C REQUEST SIGNAL

When A/C is requested from the dash master A/C switch, the A/C request signal is sent to the BCM. The BCM will then

send a command via the serial data line to the PCM. The PCM will then supply a earth signal to the A/C compressor

relay, to energise the A/C compressor.

The PCM uses this BCM serial data command to:

1. Adjust the Idle Air Control (IAC) position to compensate for the additional load placed on the engine by the air

conditioning compressor, and then

2. Energises the A/C compressor relay, to operate the A/C compressor.

Figure 6C1-1-51 A/C Request Signal Circuit With ECC

Figure 6C1-1-52 A/C Request Signal Circuit Without ECC

BATTERY VOLTAGE

The PCM continually monitor s battery voltage. W hen 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 Powertrain Control Module will

compensate by:

1. Increasing the ignition coil dwell time if the battery voltage is less 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 transmissions, Diagnostic Trouble Code (DTC) 53 will set when the ignition is

"ON'' and PCM terminal "A4'' voltage is more than 19.5 volts for about 2 seconds.

Diagnostic Trouble Code (DTC) 54 will set when the ignition is "ON'' and PCM terminal "A4'' voltage changed more than

2.5 volts in 100 milliseconds.

Diagnostic Trouble Code (DTC) 75 will set when the ignition is "ON'' and PCM terminal "A4'' voltage is less than 8.6

volts for about 4 seconds. Minimum voltage allowed for Diagnostic Trouble Code 75 to set is on a graduated scale and

will change with the temperature. Minimum voltage at -40 degrees C is 7.3 volts, minimum voltage at 90 degrees C is

8.6 volts., minimum voltage at 152 degrees C is 11.4 volts.

Figure 6C1-1-53 PCM Battery Feed

CRANKSHAFT REFERENCE SIGNAL

This also uses the camshaft position sensor signal to synchronise the fuel injector circuits for sequntial fuel injection.

The PCM also uses these reference pulses for Electronic Spark Timing (EST) operation.

For a full description of the ignition system operation refer to Section 1.7 DIRECT IGNITION SYSTEM (DIS) in this

Section.

The Direct Ignition System (DIS) sends this signal to the PCM to tell it engine RPM and crankshaft position. This signal

is a repeating series of low voltage electrical pulses generated by the ignition module. The PCM initiates fuel injector

pulses based upon receiving these crankshaft reference signal pulses.

Figure 6C1-1-54 Crankshaft Reference Signal

CRANKING SIGNAL

The cranking circuit provides an input for enabling fuel cut off during a possible backfire situation. During an engine

start, when the ignition switch is r eleas ed f r om the cr ank position bef or e the engine is running, the engine may back fire.

The Powertrain Control Module stops all injection pulses when the engine speed is less than 450 RPM, coolant

temperature is greater than -4 degrees C, a cranking signal is not received, but was received with the previous 12.5

milliseconds.

The Powertrain Control Module monitors the voltage on the cranking signal input terminal. This terminal is a voltage

sensing input.

Figure 6C1-1-55 Cranking Signal Circuit

ENGINE COOLI NG FAN SIGNAL

(LOW SPEED RESPONSE)

The V6 engine has two (2), two speed electric cooling fans which provides the primary means of moving air through the

engine radiator. These fan are placed between the radiator and the engine and has its own shroud. These fans are

used on all vehicles whether or not it is equipped with air conditioning. There is no fan in front of the A/C condenser.

The two (2), two speed electric fan's low speed can only be enabled when the engine cooling fan low speed relay is

energised by the BCM. The PCM will request low speed fan enable and disable via the serial data communication to the

BCM. After the PCM requests a change in the engine cooling fan low speed relay , the BCM will send a serial data

response message back to the PCM confirming it received the message. A failure in this response communication will

set a DTC 92. 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.

Figure 6C1-1-56 Engine Cooling Fan Signal

ENGINE COOLING FAN HIGH SPEED

The engine cooling fan high speed is controlled by the PCM based on input from the Engine Coolant Temperature

Sensor (ECT). The PCM will only turn "ON" the engine cooling fan high speed if the engine cooling low speed fans have

been "ON" for 2 seconds and the following conditions are satisfied.

• There is a BCM message response fault which will cause a DTC 92.

• An engine coolant temperature sensor failure is detected, such as DTC 14,15,16,17.

• Coolant temperature greater than 109 degrees C.

If the fan low speed was "OFF" when the criteria was met to turn the fan high speed "ON", the fan high speed will come

"ON" 5 seconds after the fan low speed is turned "ON". The high speed engine cooling fan relay can also be enable by

the A/C Refrigerant Pressure Sensor. The A/C Refrigerant Pressure Sensor will enable high speed cooling fan, if the

A/C system pressure becomes to high.

If a failure occurs in the PCM Engine Cooling Fan Relay High Speed Control circuit, a DTC 91 will set.

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. Is shorted to earth, the fan motors could continuously run, or the fuse or fusible link

could fail.

TRANSMISSION FLUID PRESSURE (TFP) SWITCH ASSEMBLY

The Transmission Fluid Pressure Switch Assembly (TFP) is used by the PCM to sense what gear range has been

selected by the vehicle operator. The TFP is located on the transmission valve body and consists of five pressure

switches, 2 normally closed fluid pressure switches and 3 normally open fluid pressure switches combined into one unit.

The Transmission Fluid Pressure Switch Assembly is one of the inputs used by the PCM to control:

• Idle Air Control (IAC) and,

• Transmission Operation.

A failure in the TFP circuits will set a DTC 28 (Transmission Fluid Pressure Switch Assembly (TFP) circuit fault) if:

• The PCM detects an "illegal" TFP combination for five seconds.

For a full description of the TFP operation refer to

Section 1.3 TRANSMISSION INFORMATION INPUT SENSORS AND SIGNALS .

Figure 6C1-1-57 Transmission Fluid Pressure Switch Assembly Circuit

THEFT DETERRENT INPUT

When the ignition switch is turned to the “ON” position, the BCM polls the PCM and sends an encrypted BCM / key

security code. The security code is received by the BCM, via the remote key reader (slip ring) or via the remote receiver

in the event of no slip ring communication.

The PCM compares the received security code with its stored security code and if matched, the PCM will continue to

enable injector fuelling and engine crank.

The PCM will return a Valid Code message (OK TO START), which tells the BCM to jump to the short loop mode to the

long loop mode.

When the ignition switch is turned from the OFF position to the ON position, the BCM will communicate with the PCM

for antitheft purposes. If the BCM does not receive the message OK TO START from the PCM within 0.5 seconds of

the ignition being switched on, the auxiliary bus is isolated via switching within the BCM.

The isolation of the auxiliary data bus during this period eliminates the possibility of a device failure other than the BCM

or PCM causing a problem on the bus and inhibiting antitheft communications.

This period is known as “Short Loop Time”, and continues until the PCM responds with an acknowledgment or a

maximum of 5 seconds, after which the BCM will switch to the standard poling sequence.

Following successful antitheft communications, the BCM begins sequential poling of devices on the bus and normal

system operation is established.

Figure 6C1-1-58 Theft Deterrent System

Figure 6C1-1-59 Theft Deterrent Serial Data Circuit

1.3 TRANSMISSION INFORMATION INPUT SENSORS AND SIGNALS

The computer used with Sequential Fuel Injected (SFI) petrol engine is called a Powertrain Control Module (PCM) and

controls a number of engine functions such as: fuel control, and ignition timing, in addition to the transmission functions.

The diagnosis of this transmission requires the availability of a Tech 2 scan tool to interface with the Powertrain Control

Module (PCM).

The transmission control system of the electronic control module has software and hardware that monitors a number of

engine and vehicle functions then uses the data to control the following operations:

• Transmission Converter Clutch (TCC) engagement.

• Upshift pattern.

• Downshift pattern.

•Line pressure to control shift quality.

Figure 6C1-1-60 Transmission Electronic Component Location View

Figure 6C1-1-61 Transmission Wiring

INFORMATION SENSORS

The PCM uses the following information sensors and switches to gather data for electronically controlling transmission

functions.

• Engine Coolant Temperature (ECT) sensor.

• Engine Speed.

• Fluid Pressure Switch Assembly.

• Throttle Position (TP) Sensor.

• Transmission Fluid Temperature (TFT) sensor.

• Transmission Economy/Power Switch.

•Vehicle Speed Sensor (VSS).

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

ECT sensor information is also used for engine functions as well as for the transmission management system. For ECT

details, refer to 1.2 ENGINE INFORMATION SENSORS AND SIGNALS in this Section.

TRANSMISSION FLUID PRESSURE (TFP) SWITCH ASSEMBLY

Figure 6C1-1-62 Transmission Fluid Pressure Switch Assembly (TFP) and Transmission Fluid Temperature Sensor

Figure 6C1-1-63 Transmission Fluid Pressure Switch Assembly (TFP) Switches

This gear range sensing device called a

Transmission Fluid Pressure Switch Assembly

(TFP) is used by the PCM to sense what gear

range has been selected by the vehicle operator.

The T FP is located on the valve body and consists

of five pressure switches, 2 normally closed and 3

normally open, combined into one unit.

The normally open fluid pressure switches are the

"D4", "LO" and "Reverse" fluid pressure switches.

They are normally open and electrical current is

stopped at these switches when no fluid pressure is

present. Fluid pressure moves the diaphragm and

contact element until the contact element touches

both the positive contact and the earth contact.

This creates a closed circuit and allows current to

flow from the positive contact, through the switch

and to earth. The normally closed fluid pressure

switches are the "D2" and "D3" fluid pressure

switches. They are normally closed and electrical

current is free to flow from the positive contact to

the earth contact when no f luid pressur e is pres ent.

Fluid pressure moves the diaphragm to disconnect

the positive and earth contacts. This opens the

switch and stops current from flowing through the

switch.

The PCM applies system voltage to the TFP on

three separate wires. An open circuit measures 12

volts while an earthed circ uit m easures 0 volts. T he

switches are opened or closed by fluid pressure.

The combination of which switches are open and

closed is used by the PCM to determine actual

manual valve position. The TFP however cannot

distinguish between park and neutral because the

monitored valve body pressures are identical in

both cases.

L -This switch will have hydraulic pressure

applied to it in m anual 1st gear only and will be

closed.

R -This switch will have hydraulic pressure

applied to it in reverse only and will be closed.

Figure 6C1-1-64 Transmission Fluid Pressure Switch

Assembly (TFP)

D2 -This switch will have hydraulic pressure

applied to it in manual 1st and 2nd gear and

will be open.

D3 -This switch will have hydraulic pressure

applied to it in manual 1st, 2nd and 3r

gear

and will be open.

D4 -This switch will have hydraulic pressure

applied to it in all drive gears except reverse

and will be closed.

TFP assembly signal voltage can be measured with

a high impedance digital volt ohmmeter by back

probing the PCM then taking measurements from

each terminal to earth, and comparing it to the

combination chart. On the transmission wiring

harness, pin N is "Range Signal A", pin R is "Range

Signal B", and pin P is "Range Signal C". With the

wiring harness connected and engine operating, a

voltage measurement of these three lines will

indicate a "high" reading (near 12 volts) when a

circuit is open, and a low (zero volts) when the

circuit is switched to earth.

These TFP inputs are used to help control line

pressure, torque converter clutch apply and shift

solenoid operation. To monitor TFP assembly

operation, the PCM compares the actual voltage

combination of the switches to a TFP combination

chart stored in its mem ory. If the PCM detects one

of two "illegal" voltage combinations a Diagnostic

Trouble Code 28 will result.

Figure 6C1-1-65 Pressure Applied to TFP Switches

There are two possible combinations of the

switches within the pressure switch assembly that

do not represent an actual gear range. If either of

these combinations are detected by the PCM for 5

seconds or longer, Diagnostic Trouble Code 28 will

set. Diagnostic Trouble Code 28 will also set if a

valid gear range combination appears at the wrong

time.

While Diagnostic Trouble Code 28 is present, the

PCM will take the following action:

1. Assume D4 for shift pattern control.

2. Use D2 pressure table.

3. Inhibit 4th gear operation in hot mode only.

4. Inhibit TCC operation.

If the TFP resumes normal functioning, the

transm ission will resum e norm al operation after the

next ignition cycle.

DTC 28 will not detect an open circuit in either

range signal "B" or "C". An open circuit in either of

these signals will not be an illegal T FP com bination

but a legal TFP combination at the wrong time, so

that the PCM interprets wrong information.

Figure 6C1-1-66 TFP Chart

There ar e two failures in the T FP that will cause an

unusual complaint. If the range signal "B" is open

the PCM will interpret this PRNDL select as "2"

gear in park or neutral with the ignition "ON" or

engine idling. The customer will probably complain

that when "D" range is selected the transmission

never shif ts into 4th gear. T his is becaus e the PCM

only controls shif ts in "D" range, but because of the

open circuit in range signal "B" the PCM interprets

this as "3" gear and the tr ans miss ion will never s hif t

to fourth gear because this "3" gear input is a

normal condition.

The other condition to cause an unusual complaint

is an open in the range signal "C". When the dr iver

selects "3" gear range, the PCM will interpret this

PRNDL select as "2" gear and will provide 1st and

2nd gears only. If the driver selects "D" range, the

transmission will have all gears and TCC, but the

Tech 2 scan tool will read P-N all the time.

Figure 6C1-1-67 Transmission Fluid Pressure Switch

Assembly (TFP) Location

TRANSMISSION FLUID TEMPERATURE (TFT) SENSOR

Figure 6C1-1-68 Transmission Fluid Pressure Switch Assembly (TFP) and Transmission Fluid Temperature Sensor

Figure 6C1-1-69 Transmission Fluid Pressure Switch Assembly (TFP) Switch Voltages

The Transm ission Fluid Temperature (T FT) sensor

is a thermistor (a res istor that changes value based

temperature) that is part of the transmission fluid

Pressure Switch Assembly (TFP). Low

transmission fluid temperature produces high

resistance and high transmission fluid temperature

produces low resistance. The PCM supplies a 5

volt signal to the Transmission Fluid Temperature

(TFT) sensor through an internal resistor then

measures the voltage drop in the circuit. Voltage

will be high when the transmission fluid is cold and

low when the transmission fluid is hot.

The PCM uses the Transmission Fluid

Temperature (TFT) Sensor to regulate torque

converter clutch apply, as well as shift quality.

Diagnostic T rouble Code 58 and 59 indic ate a fault

in the Transmission Fluid Temperature (TFT)

sensor circuit. The Tech 2 scan tool will display

transmission fluid temperature in degrees Celsius.

After the vehicle has been started, transmission

fluid temperature should rise steadily and stabilize

between 82 and 94 degrees Celsius, depending on

load.

Figure 6C1-1-70 Transmission Fluid Temperature Sensor

Both diagnostic trouble codes will cause the PCM

to use a default value of 130 degrees Celsius thus

reacting as if the transmission were hot in either

case. W hen Diagnostic Trouble Code 58 or 59 are

set the torque converter clutch is enabled in

second, third and forth and will apply early. Some

driveability symptoms will be noticed especially

when cold.

DTC 79 is used to identify if the transmission fluid

has been overheated to the point that the f luid is no

longer useable for the transmission. DTC 79 will set

if the transmission fluid temperature exceeds 146

degrees C and does not go lower than 137 degrees

C for 30 minutes.

The PCM m onitors the TFT sensor for determ ining

DTC 79. An electrical failure in the TFT sensor

circuit will not set a DTC 79. DTC 79 will only be set

if the fluid actually did exceed the temperature or if

the TFT sensor is skewed high or stuck above the

temperature threshold.

Temperature to Resistance specification chart

found at DTC 58 and DTC 59.

Figure 6C1-1-71 TFT Sensor Temperature to Resistance

Relationship

THROTTLE POSITION (TP) SENSOR

TP sensor information is also used for engine

functions as well as for the transmission

management system. For TP details, refer to

1.2 ENGINE INFORMATION SENSORS AND

SIGNALS in this Section.

TRANSMISSION ECONOMY/POWER SWITCH

The economy/power switch is used to modify

upshifts and shift times slightly. The driver can

select two transmission modes, "Economy" or

"Power" with a dash or centre console mounted

switch. The "OUT" position enables the "Power"

mode. A green indicator lamp of 1.2 watts at 12

volts is located on the right side of the instrument

cluster and displays "PWR" when illuminated to

inform the driver that the "Power" mode is now

enabled.

The PCM sends out a voltage signal, about 12

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

"Economy" 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 "Power" position the switch is

closed and the PCM voltage status signal is pulled

low, about 0.5 volts. The PCM senses this voltage

drop and enables "power" mode (alternate shift

pattern "tables" to be utilised).

In the "Power" mode, TCC can be applied in 3rd

and 4th gears. W hen TCC is applied in 3rd gear it

will stay applied until the normal 4th gear upshift

criteria are met, when the 3-4 upshift occurs the

TCC will not 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 same in

the "Economy" and "Power" modes if the TP sensor

is between 94% - 100%. The "Power" m ode should

be used when towing as applying the TCC in 3rd

and 4th gear reduces slippage in the T CC and thus

heat build up.

Figure 6C1-1-72 Transmission Economy/Power Switch

Figure 6C1-1-73 Transmission Economy/Power Switch Wiring

VEHICLE SPEED SENSOR (VSS)

The VSS information is also used for engine

functions as well as for the transmission

management system. For VSS details, refer to

1.2 ENGINE INFORMATION SENSORS AND

SIGNALS in this Section.

TRANSMISSION PASS-THRU CONNECTOR

The transmission electrical pass-thru connector is a

very important part of the HYDRA-MATIC 4L60-E

operating system.

A wiring harness electrically connects the PCM to

various sensors, solenoids, and relays within the

transmission management system. Many of the

connectors used are environmentally protected

because of the systems low voltages and low

current levels. Anything that interferes with the

electrical connec tion can cause the transm ission to

set diagnostic trouble codes and/or operate

incorrectly.

The following items can affect the electrical

connection:

• Bent pins in the connector from rough handling

during connection and disconnection.

• Wires backing away from the pins or coming

uncrimped (in either the transmission or

powertrain wiring harness).

• Dirt contamination entering the connector when

it is disconnected.

• Pins in the connector backing out of the

connector or pushed out during connection.

• Excessive transmission fluid leaking into the

connector, wicking up into the powertrain wiring

harness and degrading the wire insulation.

• Water/moisture intrusion in the connector.

• Low pin retention from excessive connection

and disconnection of the wiring harness.

• Pin corrosion from contamination.

The presence of transmission fluid in the

transmission connector is not harmful.

The fluid only affects the vehicle harness wiring

insulation if the fluid wicks up that far.

Points to remember when working with the

transmission electrical connector:

• To rem ove the connector, squeeze the two tabs

towards each other and pull straight up.

• Carefully limit twisting or wiggling the connector

during removal. This can bend pins.

• DO NOT pry the connector off with a

screwdriver or other tool.

• To install the connector, first orient 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 mating parts.

• The connector should click into place with a

positive feel and/or noise.

• Whenever the trans mis sion pass thru connec tor

is disconnected from the transmission and the

ignition is switched "ON" or the engine is

started, numerous DTC's will be set.

Figure 6C1-1-74 YB129 Powertrain Harness Connector

1.4 TRANSMISSION OUTP UTS CONTROLLED BY THE PCM

PRESSURE CONTROL SOLENOID

The transmission Pressure Control Solenoid (PC

SOL) is an electronic pressure regulator that

controls pressure based on current flow through its

coil winding. The magnetic field produced by the

coil moves the solenoid's internal valve that varies

pressure to the pressure regulator valve.

The pressure control solenoid takes the place of

the throttle valve used on past model 4L60

transmissions, used in previous "V" car models.

The PCM varies line pressure based on engine

load. Engine load is calculated from various inputs

including the TP and MAF sensors. The

transmission line pressure is actually varied by the

PCM's control of the pressure control solenoid and

its ability to change the amperage applied to the

pressure control solenoid from 0 amps (high line

pressure) to 1.1 amps (low line pressure). This

changes the duty cycle of the solenoid, which can

range between 0% and 100%. Figure 6C1-1-75 Pressure Control Solenoid

There is one Diagnostic Trouble Code associated

with the pressure control solenoid Diagnostic

Trouble Code (DTC) 73. Diagnostic Trouble Code

73 will set when the PCM detects a difference of

0.16 amp or more between the amperage

commanded and actual amperage. While the

Diagnostic Trouble Code 73 is set, the pressure

control solenoid will be turned "OFF" creating

maximum line pressure. Recovery can occur after

the next ignition cycle. Diagnostic Trouble Code 73

will not sense a stuck valve.

Figure 6C1-1-76 Pressure Control Solenoid Cutawa y View

SHIFT SOLENOIDS

The 1-2 Shift Solenoid and 2-3 Shift Solenoid are

identical in operation solenoid devices that control

the movement of the 1-2 and 2-3 shift valves (the

3-4 shift valve is not directly controlled by a shift

solenoid). The solenoids are normally open

exhaust valves that work in four combinations to

shift the transmission into different gears. PCM

controlled shift solenoids eliminate the need for

Throttle Valve (TV) and governor pressures to

control shift valve operation.

IMPORTANT:

The PCM does NOT have total control of shifting

the transmission. The manual valve can

hydraulically override the shift solenoids. Only in

"D" are the PCM and shift solenoids totally

determ ining what gear the transm ission is in. In the

manual positions "3", "2", and "1", the transm ission

manual valve position will change fluid direction in

the valve body. The transmission will shift on its

own hydraulically, the PCM will have limited control

and will respond to the hydraulic changes of the

manual valve. The PCM will change the shift

solenoids when the pressure switch assembly

(TFP), throttle position and vehicle speeds fall into

the correct ranges for PCM control. In other words

the PCM "catches up" to what happened

hydraulically. This is impor tant to rem ember , as the

Tech 2 scan tool will only display the commanded

state of the shift solenoids not the actual gear the

transmission is in.

Figure 6C1-1-77 Shift Solenoids

1-2 SHIFT SOLENOID

The 1-2 shift s olenoid is attached to the valve body

and is a normally open exhaust valve. The PCM

activates the solenoid by earthing it through an

internal Quad Driver Module (QDM). The 1-2 shift

solenoid is "ON" in 1st and 4th gear, and "OFF" in

2nd and 3rd gears. When "ON," the solenoid

redirects fluid to act on the shift valves.

There is one Diagnostic Trouble Code associated

with the 1-2 shift Solenoid, Diagnostic Trouble

Code 82. The PCM continually monitors the 1-2

shift solenoid circuit for expected voltage ("OFF"

high "ON" low). If the voltage r eading is not what is

expected on the circuit, Diagnostic Trouble Code

82 will set. While Diagnostic Trouble Code 82 is

present, high line pressure will be set and the

vehicle will have 2nd or 3rd gear only or 1st and 4th

gears only. When the fault is removed, recovery will

occur on the next ignition cycle. Figure 6C1-1-78 Shift Solenoid Cutaway View

2-3 SHIFT SOLENOID

The 2-3 shift s olenoid is attached to the valve body

and is a normally open exhaust valve. The PCM

activates the solenoid by earthling it through an

internal Quad Driver Module (QDM). The 2-3 shift

solenoid is "ON" in 1st and 2nd gear and "OFF" in

3rd and 4th gear. When "ON," the shift solenoid

redirects fluid to act on the shift valves.

There is one Diagnostic Trouble Code (DTC)

associated with the 2-3 shift Solenoid, DT C 81. 2-3

shift solenoid circuit fault. The PCM continually

monitors the 2-3 shift solenoid circuit for expected

voltage ("OFF" high "ON" low). If the voltage

reading is not what is expected, DTC 81 will set.

While DTC 81 is present, TCC operation will be

inhibited, line pressure will be high and the

transmission will have 2nd or 3rd gear only. When

the fault is r emoved, rec overy will occur at the nex t

ignition cycle. Figure 6C1-1-79 Solenoid Status

3-2 SHIFT SOLENOID VALVES

The 3-2 shift solenoid is either "ON" or "OFF" and

is used to improve the 3-2 downshift. The 3-2 shift

solenoid uses "ON" or "O FF" to contr ol press ure so

that the release of the 3-4 clutch and the apply of

the 2-4 band are smooth. The 3-2 shift solenoid is

normally "OFF" in first gear and "ON" in all other

drive gears, except during a 3-2 downshift when the

solenoid is "OFF". The amount of "OFF" time is

determined by throttle position, vehicle speed, and

the commanded gear.

There is one Diagnostic Trouble Code (DTC)

associated with the 3-2 Shift Solenoid, DTC 66.

DTC 66 will set when the PCM detects either high

voltage when the 3-2 Shift Solenoid is com manded

"ON" or if low voltage exists on the feed back line

when the solenoid is com m anded "OFF". While the

3-2 Shift Solenoid DTC 66 is set, the solenoid will

be "OFF", When DTC 66 is set, the transmission

will have a soft landing into 3rd gear, high line

pressure and 3rd gear. W hen the fault is removed

recovery can occur after the next ignition cycle.

Figure 6C1-1-80 3-2 Shift Solenoid

Figure 6C1-1-81 3-2 Shift Solenoid Cutaway View

TORQUE CONVERTER CLUTCH (TCC) SOLENOIDS

This transmission uses two Torque Converter

Clutch (TCC) solenoids valves that are used to

control torque converter clutch apply and release.

The TCC enable solenoid has priority in applying

and releasing the torque converter clutch. "The

Torque Converter Clutch enable solenoid is a

normally open exhaust valves that is commanded

either "ON" or "OFF" by the PCM. When earthed

(energised "ON"), by the PCM, the TCC solenoid

stops converter feed from exhausting. This causes

converter feed pressure to increase and shift the

TCC valve into the apply position. This pressure

allows the TCC to couple the transm ission with the

engine for a near 100% engagement.

There are two Diagnostic Trouble Codes (DTC's)

associated with the TCC enable solenoid. The first

DTC is 67, T CC enable Solenoid Cir cuit F ault. DT C

67 is designed to detect a fault in the TCC enable

solenoid electrical circuit. While DTC 67 is set the

PCM will inhibit 4th gear if the trans miss ion is in the

hot mode, and no TCC operation. Figure 6C1-1-82 Torque Converter Clutch (TCC) Enable

Solenoid

The second DTC associated with the TCC enable

solenoid is DTC 69, TCC stuck "ON". DTC 69 is

designed to detect TCC enable solenoid that does

not disengage. It does this by monitoring engine

RPM when the TCC solenoid is com manded "ON."

If the engine speed does not rise when the TCC

solenoid is disengaged the DTC 69 is set. While

DTC 69 is set the TCC will be "ON" in all gears or

2nd, 3rd, and 4th depending upon the failure, and

the transmission will have an early shift pattern.

When the fault is removed recovery will occur on

the next ignition cycle.

Figure 6C1-1-83 TCC Solenoid Cutaway View

The Torque Converter Clutch "Pulse Width

Modulated" (PWM) solenoid is used to control the

fluid acting on the converter clutch control valve,

which then controls the TCC apply and release.

This solenoid is attached to the control valve body

assem bly within the transmiss ion. The T CC "PWM"

solenoid does not have total control over TCC

engagement. The TCC "PW M" solenoid is used as

a supplement to the TCC enable solenoid. The

TCC "PWM" solenoid is used to provide smooth

engagement of the torque converter clutch by

operating on a negative duty percent of "ON" time,

which means that the earth (negative or low) side

of the solenoid circuit is controlled by the PCM.

Therefore, the TCC "PWM" solenoid is constantly

fed approximately 12 volts to the high (positive)

side and the PCM controls the length of time the

electrical circuit path to earth is closed (i.e. duty

cycle).

When the PCM closes the solenoid earth circuit,

current flows through the TCC "PWM" solenoid,

and the earth circuit (or negative side) is at low

voltage state (0 volts and solenoid energised).

Figure 6C1-1-84 Torque Converter Clutch (TCC) "PWM"

Solenoid

Fig. 6C1-1-86 illustrates an example of the TCC

"PWM" solenoid operating with a 90% negative

duty cycle at a constant operating frequency of 32

Hz (cycles per second). The frequency means that

the solenoid is puls ed (energised) with current fr om

the PCM 32 times per second. The 90% negative

duty cycle means that during each of these 32

cycles the solenoid is energis ed (ON) and 0 volts is

measured on the low (negative) side of the circuit,

90 % of the time.

At road speeds below approximately 13 km/h, the

negative duty cycle will be 0%, which means that

no current will flow through the TCC "PWM"

solenoid, deactivating it. When in this condition,

spring force will move the plunger seating the

metering ball and blocking the filtered Actuator

Feed Limit (AFL) fluid from entering the Converter

Clutch Signal (CC SIGNAL) circuit. This action

opens the Converter Clutch Signal fluid circuit to

exhaust through the solenoid.

Above road speed of approximately 13 km/h, the

TCC "PWM" solenoid will be operating at about a

90% duty cycle. T his action will cause the m etering

ball to close off the path to exhaust, most of the

time and allow AFL fluid to flow past the metering

ball and into the CC SIGNAL circuit, in readiness

for the apply of the torque converter clutch.

Figure 6C1-1-85 Torque Converter Clutch (TCC) "PWM"

Solenoid Cutaway View

When the PCM signals TCC apply, the TCC

"PWM" solenoid operates with a variable, negative

duty cycle, ranging from 90% to 0%, with an

operating fr equency of 32 Hz. This allows the PCM

to control the current flow through the solenoid coil

according to the duty cycle it sets. This has the

effect of creating a variable magnetic field, that

magnetises the solenoid core, attracting the

metering ball to seat against spring force. A high

percentage duty cycle keeps the metering ball

seated more often, thereby creating higher TCC

signal fluid pressures.

Figure 6C1-1-86 Torque Converter Clutch (TCC) "PWM"

Solenoid Duty Cycle

TCC "PWM" SOLENOID OPERATION

When vehicle road speed rises above about 13

km/h, the PCM causes the TCC "PWM" solenoid

duty cycle to change from 0% to 90% (point "A"), in

readiness for an apply of the torque converter.

To apply the torque converter clutch, the process

the PCM adopts, is as follows;

The duty cycle is dropped to 0% (point "B") and a

measurable amount of time is allowed for the TCC

enable solenoid to turn "ON". This is shown as the

time between points "B" and "C" in Fig. 6C1-1-84

Note that, at point "C", the TCC enable solenoid is

activated.

The time from point "C" to "D" is used to allow

converter (CONV FD) f luid to build in pressure and

move the Converter Clutch Valve into the apply

position.

At this point, with the TCC enable solenoid applied,

the PCM then increases the duty cycle to about

26% (point "E"). From this point, the duty cycle is

'ramped' to around the 82% point ("E" to "F"). The

rate at which the duty cycle is increased over this

period of tim e, determ ines how quickly the value of

the regulated apply fluid increases and therefore,

how quickly the torque converter clutch is applied.

This rate of change also affects the converter

clutch apply 'feel'.

As soon as the duty cycle reaches the 82% value, it

is then immediately increased to the maximum of

90%, to achieve full apply pressur e in the regulated

apply fluid circuit (point "G").

NOTE:

that the duty cycle and apply pressure will

continually vary, depending on vehicle specif ication

and operating conditions.

The two TCC solenoids work together so that TCC

apply or releas e rate can be calibrated f or a variety

of situations.

If a fault is detected by the PCM, in the TCC

"PW M" solenoid electrical circuit, a DTC 83 will be

set. When DTC 83 is set, the PCM will inhibit 4th

gear and TCC operation if in hot mode.

Figure 6C1-1-87 Torque Converter Clutch Solenoid

Operation

1.5 FUEL CONTROL SYSTEM

PURPOSE

The purpose of closed loop fuel control is to control tailpipe emissions consisting of hydrocarbons (HC), Carbon

Monoxide (CO), and Oxides of Nitrogen (NOx). At the sam e time, the system m ust achieve good engine perform ance

and good fuel economy.

The closed loop system regulates exhaust emissions by controlling the air/fuel ratio at an optimum level during various

driving conditions. The most efficient air/fuel ratio to minimise exhaust emissions is 14.7 to 1, this allows the 3-way

catalytic converter to operate at maximum efficiency to control exhaust pollutants. Because of the constant measuring

of the exhaust gases by the oxygen sensors, and adjusting of the fuel injector pulse width by the PCM, the fuel injection

system is called a "closed-loop" control system.

FUNCTION

The f uel supply system delivers fuel at a r egulated pressur e to the fuel rail. T he fuel injec tors, located dir ectly ahead of

each inlet port of the cylinder head, act as fuel flow control valves, "spraying" atomised fuel into the inlet ports when

they are electrically "pulsed" by the PCM. On this engine, all injectors are wired individually so they are pulsed

individually. This type of fuel injection is referred to as sequential injection because pulsation of the injectors are

individually controlled and in a specific order.

The PCM controls the amount of fuel injected into the engine by controlling the length of time the injectors are held

open. This "length-of-time" is called PULSE WIDTH. To increase the amount of fuel injected, the pulse width is

lengthened, and vice versa. The pulse width is calibratable and varies between 0 - 11 milliseconds with the engine

running at idle, and injection pulses normally occur once every crankshaft revolution.

MASS AIR FLOW SYSTEM

The Holden/Delco Fuel Injection system is a Mass Air Flow system. The system is based upon an Air Meter that

measures the mass air flow rate of the engine directly.

Advantages of Mass Air Flow:

• Base engine components can be changed.

• Automatically compensates for engine aging.

• No air measurement lag time.

• Excellent idle stability.

Two spec ific data s ensors provide the PCM with the basic inf orm ation for the fuel m anagem ent por tion of its operation.

That is, two specific signals; cr ankshaf t reference signal f rom the ignition s ystem , and the Mass Air Flow (MAF) sensor

signal. Both of these signals to the PCM establish the engine speed and m ass of air ingested by the engine. Due to the

additional temperature compensation sensor in the MAF sensor, this system does not require a manifold absolute

pressure sensor.

The engine speed signal comes from the ignition module to the PCM on the crankshaft reference signal input circuit.

The PCM uses RPM information to calculate the best fuel injector pulse width and spark timing for a given operating

RPM band.

The mass of air ingested by the engine is sent as a signal from the mass air flow sensor to the PCM.

When the engine is started, the PCM will immediately look at the Engine Coolant Temperature sensor to determine how

much fuel is required to start the engine. After the engine is started, the PCM will constantly monitor the MAF sensor

values to determine both the spar k advanc e and engine f uelling r equirements . The Mass Air Flow s ens or meas ures the

mass of air ingested into the engine. The PCM then calculates how much fuel that must be injected to maintain an

air/fuel ratio of 14.7 to 1. An engine started in cold weather will require more fuel and spark advance than an engine

started hot, which requires less fuel and less spark advance.

One sensor is used to m easur e the density fac tor, the Mass Air F low (MAF) sensor. T he m ass air f low sensor used on

this engine utilises a heated element type of operation. Three sensing elements are used in this system.

As air passes over the heated elements during engine operation they begin to cool. By measuring the amount of

electrical power required to maintain the heated elements at the predetermined temperature above ambient

temperature mass air flow rate can be determined.

As the PCM receives this frequency signal from the mass air flow sensor, it searches its pre-programmed tables of

information to determine the pulse width of the fuel injectors required to match the mass air flow signals.

The signal that is sent from the mass air flow sensor is sent in the form of a frequency output. A large quantity of air

passing through the sensor (such as when accelerating) will be indicated as a high frequency output. A small quantity of

air passing thr ough the sensor will be indicated as a low frequenc y output ( such as deceleration or at idle. The Tech 2

scan tool displays MAF sensor information in frequency, grams per second. A "normal" reading is approximately 4 - 9

grams per second at idle and increases with engine RPM.

The remaining sensors and switches provide electrical inputs to the PCM which are used for modification of the air/fuel

mixture as well as for other PCM control functions, such as Idle Air Control (IAC).

MODES OF OPERATION

The PCM looks at voltage signals from several sensors to determine how much fuel to give the engine, and when to

operate in the open-loop or clos ed-loop m odes. The f uel delivery is controlled in one of s everal possible m odes. All the

modes are controlled by the PCM, and are described in the following paragraphs.

STARTING MODE

W hen the ignition key is first turned "ON," the PCM will energise the fuel pump relay, and the fuel pump will build up

pressure to the fuel rail. The PCM then checks the engine coolant temperature sensor and determines the proper

injector pulse width for starting the engine.

When cranking begins, the PCM will operate in the Starting Mode until engine RPM is more than about 400, -or- the

"Clear Flood" m ode is enabled. After the ignition is turned "ON" and the firs t refer ence signal is received, the PCM will

pulse all of the fuel injectors. After the first prime pulse has been injected, the PCM will wait until the PCM receives a

good camshaft position signal. When the PCM receives a good camshaft position signal, the PCM operates the fuel

injectors in Sequential mode. Pulse width during the Starting Mode is between approximately 4 - 26 milliseconds,

depending upon engine coolant temperature.

CLEAR FLOOD MODE

If the engine floods, it can be started by pushing the accelerator pedal down all the way to the floor while cranking the

engine. The PCM then pulses the injectors with zero millisecond pulse width, which should "clear" a flooded engine.

The PCM holds this pulse width as long as the throttle position sensor input indicates the throttle is above 80% and

RPM is below 400.

If the throttle is held wide-open w hile attempting to make a normal start w ith a non-flooded engine, the engine

will not start.

NORMAL OPEN LOOP MODE

After the engine is running ( RPM mor e than 400), the PCM will operate the f uel c ontr ol s ystem in the O pen Loop mode.

In open loop, the PCM ignores the signal f rom the O xygen Sensor (O2S) , and calc ulates the air/f uel r atio inj ector pulse

width based on inputs from the crankshaft reference signal (RPM input) and these sensors: MAF, IAT, ECT, and TP

sensor.

The system will stay in the Open Loop m ode until all the Closed Loop m ode criteria have been m et, or not at idle, ref er

Open Loop Idle Mode description.

In open loop, the calculated pulse width may give an air/fuel ratio other than 14.7 to 1. An example of this would be

when the engine is cold, because a richer mixture is needed to ensure good driveability.

The normal open loop mode is not ac tive when adverse or abnor mal vehicle oper ating c onditions ar e oc cu rr ing advers e

conditions include engine overheating due to high vehicle speed or high ambient temperature.

OPEN LOOP IDLE MODE

The reason for the Idle Mode is to allow a slightly richer mixture at idle f or better idle quality. Idle Mode air/fuel ratio is

about 14.0 to 1. This is an open loop mode, meaning the O2 sensor signal is ignored.

The Open Loop Idle Mode is in effect when the throttle is closed (TP Sensor), and vehicle speed is below 5 km/h (VSS).

In the case where the vehicle rolls to a stop while operating in the Closed Loop mode, Idle Mode will be delayed for

about 20-30 seconds. During this time, the PCM will "learn" a fuel correction factor for a 14.7 to 1 air/fuel ratio before

switching to the Idle Mode.

CLOSED LOOP MODE

In Closed Loop mode, the PCM initially calculates injector pulse width based on the same sensors used in open loop.

The difference is that in closed loop, the PCM uses the Exhaust Gas Oxygen Sensor (O2S) signal to modify and

precisely fine tune the fuel pulse width calculations in order to precisely maintain the 14.7 to 1 air/fuel ratio that allows

the catalytic converter to operate at it's maximum conversion efficiency.

DELTA TPS ACCELERATION MODE

The PCM looks at rapid changes in throttle position (TP sensor) to increase engine power, and provides extra fuel by

increasing the injector pulse width. If the increased fuel requirements are great enough, the PCM may add extra fuel

injection pulses between the injector pulses that normally occur once per crankshaft revolution.

LEAN CRUISE AIR/FUEL MODE

During steady state cruising, the air/fuel ratio is made lower in order to increase fuel economy.

The engine will operate in Lean Cruise when:

• ECT is greater than 80 degrees C.

• VSS is greater than 70 km/h.

• Engine has been running longer than 2 minutes and 30 seconds.

• Calculated A/F ratio is 14.8 to 1

• Engine is not in power enrichment mode.

If all the criteria ar e met, the PCM will lean out the A/F ratio by 0.1 ratio every 0.2 second until it r eaches its m aximum

total enleanment.

DECELERATION MODE

When deceleration occurs, the fuel remaining in the intake manifold can cause excessive emissions and possibly

back firing. Again, the PCM looks at changes in throttle position (T P sensor) and engine RPM and r educes the am ount

of fuel by decreasing the pulse width, but does not completely shut off the fuel.

DECEL FUEL CUTOFF MODE

Decel fuel cutoff disables fuel delivery during a deceleration to reduce emissions and to improve fuel economy .

When deceleration from road speed occurs, the PCM can cut off fuel pulses completely for short periods. The decel

fuel cutoff mode occurs when all these conditions are met:

1. Coolant temperature above 63 degrees C.

2. Engine RPM has dropped more than 200 RPM.

3. Vehicle speed above 42 km/h.

4. Throttle is less than 2 %.

When the decel fuel cutoff is in effect, any one of these can cause the injection pulses to restart.

1. Engine RPM has not dropped more than 200 RPM.

2. Vehicle speed is less than 42 km/h.

3. Throttle is open at least 2%.

PARK/NEUTRAL TO DRIVE ACCELERATION ENRICHMENT MODE

The PCM will deliver additional fuel to the engine to reduce the RPM droop associated with a transmission shift from

park/neutral to a drive shift. This mode will only add fuel based on the first 32 reference pulses after a shift has been

detected.

POWER ENRICHMENT (PE) MODE

The Power Enrichment (PE) mode delivers a rich mixture to the cylinders during a large throttle position change

command from the driver. During PE, the PCM will not make fuelling changes based on the oxygen sensor signal.

BATTERY VOLTAGE CORRECTION MODE

At low battery voltages, the ignition system may deliver a weak spark, and the injector mechanical movement takes

longer to "open." The PCM will compensate by:

• Increasing ignition coil dwell time if voltage is less than 12 volts.

• Increasing idle RPM if voltage drops below 10 volts.

• Increasing injector pulse width if voltage drops below 10 volts.

FUEL CUTOFF MODE

No fuel is delivered by the injectors when the ignition is (OFF). This prevents dieseling. Also, fuel pulses are not

delivered if the PCM receives no distributor reference pulses from the ignition module, which means the engine is not

running.

The Fuel Cutoff Mode is also enabled at:

• High engine RPM, as an overspeed protection for the engine. When cutoff is in effect due to high RPM, injection

pulses will resume after engine RPM drops slightly.

• High vehicle speed. W hen the vehicle speed exceeds a calibratable value the fuel base pulse width is set equal to

zero. Normal fuel operation will return when the vehicle speed falls below a calibratable value.

SEQUENTIAL FUEL INJECTION MODE

When the engine is first cranked over, all injectors will be energised simultaneously. After the engine has been started

and a good camshaft signal has been processed, the PCM will energise each individual injector in the normal firing

order. This mode of operation helps to stabilize idle, reduce emissions and reduce fluctuations in fuel pressure.

CAMSHAFT POSITION SENSOR

The Camshaft Position Sensor is located in the

engine front cover, behind and below the water

pump, near the camshaft sprocket.

As the camshaf t spr ock et turns, a m agnet m ounted

on it activates the Hall Ef f ec t s witch in the c amshaft

position sensor. When the Hall Effect switch is

activated, it earth's the signal line to the DIS

module, pulling the camshaft position signal line's

applied voltage low. This is interpreted as a

camshaft position signal (Synchronisation Pulse).

Because of the way the signal is created by the

camshaft position sensor, the signal circuit is

always either at a high or low voltage (square wave

signal).

While the camshaft sprocket continues to turn, the

Hall Eff ect switch turns "OFF" as the m agnetic f ield

passes the camshaft position sensor, resulting in

one signal each time the camshaft makes one

revolution.

The camshaft position signal, which actually

represents camshaft position due to the sensor's

mounting location, is used by the PCM to properly

time its sequential fuel injection operation.

Refer to Figs. 6C-1-1-18 and 6C1-1-19 in this

Section for camshaft position sensor location and

camshaft position signal details.

When the camshaft position signal is not received

by the PCM, a DTC 48 will be set. An intermittent

cam shaft position signal will set a DT C 49. If either

of these DTC's are set, the fuel system will not be

in sequential fuel injection mode.

Figure 6C1-1-88 Camshaft Position Sensor

ADAPTIVE LEARNING

Adaptive learning is the ability of the on-board

computer to determine and remember its most

recent operating experience. The PCM uses this

rem ember ed inform ation to "learn f rom experienc e"

and to make adjustments with respect to what it

learnt. If the engine were to develop a restricted

fuel filter, the PCM will change the fuel injector

pulse width richer to compensate for this condition

and will reme m ber to k eep this f uel inj ector pulse in

memory until the restriction is corrected. After the

restriction has been fixed, the PCM will eventually

go back to the original pre-programmed fuel injector

pulse.

Adaptive learning is an on-going process that

continues throughout the life of the engine. A new

engine with good compression will have good

vacuum. As the engine wears and compression

decreases, a slight decrease in engine vacuum will

be noticed, which translates into a slightly lower

MAF grams per second at idle, which will decrease

injector pulse width to compensate for this

condition.

SHORT TERM FUEL TRIM

Short Term Fuel Trim (STFT) represents short term corrections to the fuel injector pulse width calculations, based on

the oxygen sensor input signal to the PCM.

When the engine is started cold, in "Open Loop," the PCM will control the fuel injection pulse width based upon various

sensor inputs such as RPM, ECT, MAF and TP sensor until the oxygen sensors become hot enough (approximately

315 degrees C) to operate properly. During this "Open Loop" period, both Short Term Fuel Trim (STFT) and Long Term

Fuel Trim (LTFT) are disabled and will read 0% on a Tech 2 scan tool.

When the oxygen sensor has come up to its normal operating temperature (approximately 600 degrees C or above), it

will produce a varying voltage to the PCM and provide a good indication of what has happened in the combustion

chambers.

At this time the PCM will switch from "Open Loop" to "Closed Loop" and the STFT will start to constantly monitor the

oxygen sensor signal, so that the PCM can modify fuel injector pulse width with greater accuracy than in "Open Loop".

STFT monitors the oxygen sensor signal so that it can adjust the fuel injector pulse width to maintain an air/fuel ratio of

14.7 to 1 for maximum catalytic converter efficiency. An STFT value of 0% is equivalent to an air/fuel ratio of 14.7 to 1

and an average oxygen sensor signal voltage of 450 mV.

The normal position for Short Term Fuel Trim is 0%, any change from this value indicates the Short Term Fuel Trim is

changing the fuel injector pulse width. The amount of pulse width change depends upon how far the STFT value is from

0%. If the STFT value is above 0%, the fuel injector pulse width is being increased, thus adding more fuel. If the STFT

value is below 0%, the fuel injector pulse width is being decreased, thus removing fuel. The normal operating range of

STFT is considered to be between -22% and +25% ; any value out of this range is usually caused by a malfunction.

If an engine has a restricted fuel filter, the low fuel pressure will result in less fuel being injected and allows more air into

the air charge than is needed to ignite the amount of fuel the fuel injector has injected, therefore, a lean air/fuel ratio

exists in the combustion chamber. After combustion has taken place, the exhaust gases still contain more oxygen

content than normal and the oxygen sensor reads this as low voltage, say 200 mV. The STFT detects that the oxygen

sensor signal is low and will increase the value to richen up the air/fuel mixture. On a Tech 2 scan tool it will display

STFT as a value above 0%. This STFT change will increase the injector pulse width allowing the fuel injectors to stay

open longer and inject more fuel.

If the additional fuel was injected and the oxygen sensor signal voltage is still low, the STFT will continue to increase its

value until the oxygen sensor signal voltage goes above 450 mV. If the STFT continues to detect a low oxygen sensor

signal voltage it will continue to try and compensate for the lean exhaust condition until it runs out of its authority in the

particular Long Term Fuel Trim (LTFT) cell it's operating in. At this point, the PCM will reset STFT to 0% and go through

this procedure again until it can control the system.

If after a specified amount of resets have been tried and failed, the PCM knows that it cannot control for the failure and

the STFT will remain at its maximum value.

STFT values are based on the oxygen sensor signal voltage reading, therefore, STFT is used by the PCM to make

quick changes to the fuel injector pulse width over a short period of time.

LONG TERM FUEL TRIM

Long Term Fuel Trim is used to adjust for engine to engine variation and to adjust for engine aging. LTFT is a portion of

the PCM memory used to adjust fuel delivery across all operating conditions of the engine. The PCM monitors the

STFT and will adjust the long term trend of the fuel injector pulse width if the STFT has been at a value for a certain

period of time. LTFT is used to change the long term fuel injector pulse width and is only operational w hen the fuel

control system is in "Closed Loop." A normal LTFT value is 0% and should follow the STFT value.

If an engine has a restricted fuel filter, the low fuel pressure will result in less fuel being injected and will cause the

STFT value to go higher than 0%, say 2%. If this STFT value change does not compensate for the restricted fuel filter,

the PCM will continue to increase the STFT value. The STFT may climb as high as its maximum calibrated value if

there is a severe restriction. The PCM will continue to monitor STFT as it climbs, but it will not make any changes to the

fuel injector pulse width for a specific period of time. After a specific period of time has elapsed and the STFT value has

remained above say +8%, the LTFT will move up to say 4% and wait again to detect if the STFT has dropped back

down to 0%. If not, the STFT will gradually move toward its maximum calibrated value limit until it gains control of the

fuel injection system. If STFT and LTFT are both set at their maximum value limit, the fuel control system is "out of the

limits of control" and will set either a Diagnostic Trouble Code (DTC) 44, or DTC 64 (lean exhaust) or DTC 45, or DTC

65 (rich exhaust) and go into "open loop" operation. Under the conditions of power enrichment, (Wide Open Throttle,

WOT), the PCM sets the STFT to 0% and freezes it there until power enrichment is no longer in effect. This is done so

that LTFT will not try to correct for the commanded richness of power enrichment.

The PCM will keep the latest LTFT values stored in its LTFT memory cells. MAF sensor readings and engine RPM are

used by the LTFT to determine what cell to read. LTFT values are stored in the PCM's long term memory, for use each

time the engine's RPM and load matches one of the LTFT cells. All LTFT values are reset to 0% when the PCM's "long

term memory power supply" is disconnected, as when diagnostic trouble codes are cleared. The Tech 2 scan tool also

has the ability to reset LTFT to 0% with a special command.

Figure 6C1-1-89 Long Term Fuel Trim Values

LONG TERM FUEL TRIM CELLS

The Long Term Fuel Trim function of the PCM is divided up into cells arranged by a Mass Air Flow (MAF) and Engine

Speed (RPM). Each cell corresponds to a region on a MAF vs RPM table. Each region is calibrated to a LTFT value of

0%. A value of 0% in a given block indicates no fuel adjustment is needed for that engine load condition. A higher

number, say + 4%, indicates that the PCM has detected a lean exhaust indication under those conditions, and is adding

fuel (increasing fuel injector pulse width) to compensate. Conversely, a lower number, say -6%, indicates that the PCM

has detected a rich exhaust indication under those load conditions, and is subtracting fuel (decreasing fuel injector

pulse width) to compensate.

As the vehicle is driven from a standing start and accelerated or decelerated from various engine speeds, the engine's

LTFT calibration will change from one cell to another cell. As the LTFT changes cell so does STFT, however, STFT will

only make short term corrections in whatever LTFT cell the engine is operating in. When the engine is idling, it can be in

one of two cells. On a vehicle with automatic transmission, depending upon canister purge, the engine will idle in cell 0

or 17. If the engine was running at idle and the canister purge was "ON", we would be in cell number 0 on an automatic

transmission equipped vehicle. Cells 16 and 33 are used for idle on vehicles with manual transmission only. Whatever

cell the engine is operating in, the PCM will read that cell's particular LTFT value and electronically adjust the fuel

injector base pulse width to compensate for a rich or lean condition in the engine. If an engine has a restricted fuel filter

and the customer has driven the vehicle like this for quite some time, the STFT value would be high, and the PCM

would be compensating for this condition by adding more fuel. Because the STFT value is above 0%, LTFT will also be

greater than 0% in most of the cells to compensate for the lean exhaust. If you suspect a driveability problem

associated with an over rich or over lean condition, then use the STFT value to detect what the fuel control system is

doing at the present time. Use the LTFT to identify what the system has "learned" over a greater period of time to

compensate for the condition.

Use the LTFT cells to determine if the fuel control system is commanding rich or lean throughout the operating range. If

it is only rich or lean at idle or part throttle, look for components that would cause problems in these areas.

All LTFT cell values are reset to 0% when long term memory power to the PCM is removed, such as when clearing

DTC's.

The Tech 2 scan tool has the ability to reset all LTFT cells to 0% with a special command.

Figure 6C1-1-90 Long Term Fuel Trim Cell Matrix

BASIC FUEL SYSTEM OPERATION

The fuel control system starts with the fuel in the fuel tank. A single in-tank high pressure fuel pump (located inside a

modular sender unit) is used. From the high pressure pump, fuel flows through a fuel filter, then on to the engine fuel

rail through the fuel pressure supply line.

The high pressure in-tank single pump is capable of providing fuel at more than 414 kPa. A pressure regulator connects

between the fuel rail and the return fuel line, and keeps fuel available to the injectors at a regulated pressure between

270 and 350 kPa for the Non-Supercharged Engine, and 290 and 410 kPa for the Supercharged Engine application.

The regulated pressure will vary , depending on intake manifold pressure. The pressure regulator senses manifold

pressure through a small hose connecting it to the throttle body adapter. When throttle body adapter pressure is low

(closed-throttle), the regulated pressure is at its lowest. When the throttle is wide open, intake manifold pressure is high

and the fuel pressure also is at its highest.

Fuel in excess of injector needs is returned to the fuel tank by the separate return line connected to the outlet of the

pressure regulator.

The injectors, located in each runner of the intake manifold just ahead of the inlet ports to the cylinder head, are

controlled by the PCM. They deliver fuel in one of several modes, as described previously.

The fuel pump is energised by the PCM via the fuel pump relay. Refer to Diagnosis CHA RT A 4.1 for Non-

Supercharged Engine and Chart A 4.1-1 for Supercharged Engine for further diagnosis of the fuel pump electrical

system.

SYSTEM COMPONENTS

The Fuel Control System is made up of the following components:

• PCM

• Fuel pressure supply line

• Fuel pump relay

• Fuel Pump Control Module (Supercharged Engine Only)

• Fuel rail

• Injectors

• Modular Fuel Sender Assembly

• Fuel Pump

• Fuel pressure regulator

• Fuel filter

• Fuel return line

• Swirl pot

Figure 6C1-1-91 Fuel Delivery System

MODULAR FUEL SENDER ASSEMBLY

The modular fuel sender assembly is attached to

the top of the f uel tank , and ex tends f r om the top of

the fuel tank to the bottom.

The modular fuel sender assembly consists of the

following major components:

• A Fuel Sender Cover

• Fuel Pipes (above cover)

• A Fuel Pump

• A Fuel Pump Strainer

• A Fuel Pump Reservoir

• A Fuel Sender Strainer

• A filter to reduce radio fr equency interferenc e on

Supercharged Engine models

• A Ceramic Fuel Level Sensor Assembly

The fuel level sender assembly consists of the

following:

• A Float

• The Wire Float Arm

• A Rheostat

The fuel level is sensed by the position of the float

and float arm, position changes, the amount of

current passing through the rheostat varies, thus

changing the fuel gauge reading on the instrument

panel.

The V6 Non-Superc harged Engine applic ation uses

a GEN. III TURBINE fuel pump, and can be

serviced separately from the sender unit assembly.

The V6 Supercharged Engine application uses a

ROLLERVANE fuel pum p. This fuel pump c an only

be serviced as a complete unit with the sender unit

assembly.

Figure 6C1-1-92 Modular Sender Assembly

Figure 6C1-1-93 Fuel Pump/Sender Assembly

Figure 6C1-1-94-A Supercharged Engine Rollervane Fuel Pump Assembly

Figure 6C1-1-95 Non-Supercharged Engine GEN. III Turbine Fuel Pump Assembly

THROTTLE BODY UNIT

The throttle body unit is made up of one casting

assembly, with two electrical components

connected to it. They are:

1. An Idle Air Control (IAC) valve to control air

flow bypassing around the throttle blade. This

"bypass" airflow provides the air requirements

for the engine when the throttle is closed.

More "bypass" air gives the engine the ability

of a higher idle speed, while lower flow rates of

this "bypass" air give lower idle speeds. The

IAC acts as an PCM-controlled bypass air

valve, allowing the PCM to control idle speed.

2. A Throttle Position Sensor, which gives the

PCM information about current throttle

position, and if the throttle is moving (opening

or closing). The PCM can also determine how

quickly the throttle is opening or closing with

this signal.

The throttle body contains 2 vacuum ports. The

small port provides manifold vacuum to the

evaporative emission's canister purge solenoid.

The larger port is for the positive crankcase

ventilation system.

Figure 6C1-1-96 Throttle Body with TPS and IAC

There are specific throttle body assemblies for

vehicles with automatic and manual transmission.

Identification is by a drill point marking on the

throttle used for vehicles with manual transmission.

Figure 6C1-1-97 Throttle Body Identification

FUEL INJECTORS

The fuel injectors are electrically operated fuel flow

control valves. They are supplied with +12 volts

through a Fuse and EFI relay, both located in the

engine compartment fuse and relay housing. The

injectors are controlled by the PCM providing the

earth circuit. The PCM energises the injectors to

"open" the flow of f uel. The injector s are never fully

energised "ON," as that would flood the engine with

too much fuel. The PCM supplies the earth circuit

in short pulses. The longer the

duration of the puls e (pulse width), the m ore fuel is

injected into the engine. Inside, the injector s have a

coil of electrical wire that becomes an

electromagnet when energised. The resistance of

these windings is im portant for the PCM to operate

correctly. The injector electrical resistance is

approximately 12.2 ohms at 20 C. If

measurement with an accurate ohmmeter

shows less than 11.8 ohms or more than 12.8

ohms, replace the injector.

(Acceptable: 11.8-12.8 ohms)

A fuel injector that does not open causes a misfire

condition. An injector which is stuck partly open

could caus e dieseling because som e fuel would be

delivered to the engine after the ignition key is

turned "OFF."

Figure 6C1-1-98 Fuel Injector

Figure 6C1-1-99 Injector Circuit

FUEL PRESSURE REGULATOR

The fuel pressure regulator is a diaphragm-

operated relief valve with fuel pump pressure on

one side and intake manifold pressure (engine

vacuum) combined with mechanical spring

pressur e on the other. The func tion of the regulator

is to maintain a regulated pressure at the injectors

at all times by controlling the flow into the return

line.

The fuel pressure regulator is mounted on the fuel

rail and may be serviced separately.

If the fuel pressure is too low, poor performance

and a DTC 44, or 64 could set. If the pressure is

too high, excessive odour and a DTC 45, or 65 may

result. Refer to Chart A-4.1 (Non-Supercharged

Engine) or Chart A-4.1-1 (Supercharged Engine)

for information on diagnosing fuel pressure

conditions.

Figure 6C1-1-100-Typical Fuel Pressure Regulator

Figure 6C1-1-101 Fuel Pressure Regulator Location

Supercharged Engine

Figure 6C1-1-102 Fuel Pressure Regulator Location

Non-Supercharged Engine

FUEL FILTER

The f uel f ilter is located under the vehic le by the left

hand rear side frame, forward of the fuel tank.

The fuel filter is mounted in place by a plastic

retaining strap attac hed to the rear fr am e. Both fuel

pressure hoses at the filter are quick connects to

the filter. T hese quick connections can be rem oved

by squeezing the oval shaped connections at the

filter.

For removal of the fuel filter, refer to

Section 6C1-3 SERVICE OPERATIONS in this

Section.

Figure 6C1-1-103 Fuel Filter Location

FUEL PUMP ELECTRICA L CIRCUITS (NON-SUPERCHARGED ENGINE)

When the ignition switch is turned to "ON" or 'crank' after having been "OFF" for at least 10 seconds, the PCM will

immediately energise the fuel pump relay to operate the fuel pump. This builds up the fuel pressure quickly. If the

engine is not cranked within two seconds, the PCM will shut the fuel pump relay "OFF" and wait until the engine is

crank ed. As soon as the engine begins c ranking, the PCM will sense the engine turning f rom the cranks haft ref erence

input, and turn the relay "ON" again to run the fuel pump.

A failed fuel pump relay circuit will cause a no start condition. Refer to Figure 6C1-1-106 for fuel pump relay location.

Figure 6C1-1-104 Fuel Pump Electrical Circuits Non-Supercharged Engine

FUEL PUMP ELECTRICAL CIRCUITS (SUPERCHARGED ENGINE)

When the ignition switch is turned to "ON" or 'crank' after having been "OFF" for at least 10 seconds, the PCM will

immediately energise the fuel pum p relay which will then activate the Fuel Pump Contr ol Module (Figure 6C1- 1-107) to

operate the fuel pump. This builds up the fuel pressure quickly. If the engine is not cranked within two seconds, the

PCM will shut the fuel pum p relay "OFF" and wait until the engine is cranked. As soon as the engine begins cranking,

the PCM will sense the engine turning from the c rank shaf t refer ence input, and turn the r elay "ON" again to run the fuel

pump.

A failed fuel pump relay circuit will cause a no start condition. Refer to Figure 6C1-1-106 for fuel pump relay location.

Figure 6C1-1-105 Fuel Pump Electrical Circuits Supercharged Engine

FUEL PUMP (SUPERCHARGED ENGINE)

A specific fuel pump is used for vehicles with V6

Supercharged engine. This fuel pump is a

ROLLERVANE type pump whereas the fuel pump

used for Non-Supercharged vehicles is a turbine

(GEN. III Turbine) type pump.

Identification of the fuel pum p for the superchar ged

engine over the pump used for non-supercharged

vehicles is by referring to the overall diameter of the

pump body. For supercharged applications the

pump body overall diameter is approximately 37

mm, with the fuel pump for the non-supercharged

engine application being approximately 44 mm.

The fuel pump relay is located in the engine

compartment relay housing.

Figure 6C1-1-106 Fuel Pump Relay Location

FUEL PUMP CONTROL MODULE

The V6 Supercharged engine utilises a two speed

Fuel Pump and a Fuel Pump Control module. The

Fuel Pump Control Module is located in the boot.

The Fuel Pump Control Module can vary the fuel

pump output depending on the required engine

load. When the ignition is first turned "ON", the

PCM energises the fuel pump relay which applies

power to the Fuel Pump Control Module. The fuel

pump will then pressurise the fuel system.

The purpose for the Fuel Pump Control Module is

that this Supercharged system requires more fuel

volume under heavy engine load conditions then

the non-superchar ged system . The f uel pum p used

in the non-superchar ged system m ay be capable of

supplying the required fuel volume for the

supercharged system, but with the increased fuel

volume required, the non-supercharged fuel pump

would eventually fail f rom r unning at the higher fuel

volume.

The PCM controls the current flow through the fuel

pump with a Pulsed Width Modulation (PWM)

signal at 128 Hertz (Hz) to the fuel pump control

module. T he fuel pum p control m odule controls the

current flow through the fuel pump depending on

the PWM signal received from the PCM.

Under normal driving conditions the required fuel

volume is less, so the f uel pum p operates at a duty

cycle of 67% "ON", that is the PCM controls the fuel

pump circuit, via the fuel pump control module at

67% "ON" and 33% "OFF", at a frequency of 128

Hz.

When the engine load is increased, as measured

by the Mass Air Flow sensor, the fuel pum p control

module will switch from the normal duty cycle

(67%) to a higher duty cycle (100%) based on the

com mand f r om the PCM. This higher duty cycle will

increase the current supply through the fuel pump,

increasing the fuel volume delivered by the fuel

pump.

Another feature of this Fuel Pump Control Module

is that when the fuel pump is running at the lower

duty cycle, (norm al driving conditions ), the returned

fuel to the fuel tank (from the fuel pressure

regulator) is less. This lower volume of returned

fuel to the fuel tank will result in lower emissions

(fuel tank vapours).

Also with the fuel pump running at a lower duty

cycle (normal dr iving conditions) , the voltage output

required to run the pump is lower. This will require

less generator output and will decrease overall

vehicle fuel usage.

Refer to Chart A-4.1-1 for diagnosis of the fuel

pump electrical circuit.

Figure 6C1-1-107 Fuel Pump Control Module Location

1.6 IDLE AIR CONTROL (IAC) VALVE

The purpose of the Idle Air Control (IAC) valve, is

to control engine idle speed, and prevent stalls due

to changes in engine load at idle.

The IAC valve, mounted in the throttle body,

controls bypass air around the throttle valve. By

extending the pintle (to decrease air flow) or

retracting the pintle (to increase air flow), a

controlled amount of air can move around the

throttle valve. If RPM is too low, more air is

bypassed around the throttle valve to increase

RPM. If RPM is too high, less air is bypassed

around the throttle valve to decrease RPM.

The IAC Valve moves in small steps numbered

from 0 (extended pintle, bypass air passage fully

shut) to 255 (retracted pintle, maximum bypass

airflow) as commanded by the PCM.

At idle, the desired position of the IAC valve is

calculated by the PCM based on coolant

temperature, actual engine RPM, engine load, and

battery voltage.

If the IAC Valve is disconnected or reconnected

with the engine running, the PCM can "lose track"

of the actual position of the IAC. T his also happens

when PCM's keep alive memory voltage, i.e., PCM

connectors, ENGINE fuse F31, or battery cables,

are disconnected. If this happens, the PCM will

"reset" the IAC. After the engine has been run for at

least 5 seconds, then upon ignition "OFF" the IAC

will be reset.

Figure 6C1-1-108 IAC Valve

The "reset" procedure is as follows:

The PCM commands the IAC to shut the idle air

passageway in the throttle body. It does so by

issuing enough "extend" pulses to move the IAC

pintle fully shut in the bore, regar dless of where the

actual position was. Then, the PCM calculates the

IAC is at a fully shut position, and calls that position

"0 steps." Next, the PCM issues "retract" steps to

properly position the pintle.

The IAC can also be reset with the engine running

by a special command on the Tech 2 scan tool.

The IAC valve affects only the idle RPM of the

engine. If it is open fully, too much air will be

allowed into the manif old and idle speed will be too

high. If it is stuc k closed, too little air will be allowed

into the intake manifold, and idle speed will be too

low.

Figure 6C1-1-109 IAC Valve Location

Figure 6C1-1-110 IAC Valve Circuit

1.7 DIRECT IGNITION SYSTEM (DIS)

PURPOSE

The Direct Ignition System (DIS) 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 spark advance with the DIS system.

DIS has several advantages over a mechanical

distributor system:

• No moving parts

• Less maintenance

• Remote mounting capability

• No mechanical load on the engine

• More coil cool down time between firing events

• Elimination of mechanical timing adjustments

• Increased available ignition coil saturation time

Figure 6C1-1-111 Crankshaft Sensor & Crankshaft

Balancer

OPERATION

The Direct Ignition System (DIS) is an ignition

system that does not use a conventional distributor

and ignition coil. The DIS ignition system consists

of; 3 ignition coils, a DIS m odule, a dual Hall-effect

crankshaft position sensor, an engine crankshaft

balancer with crankshaft sensor interrupter rings

attached to the rear, related connecting wires, and

the EST (electronic spark timing) portion of the

PCM. The PCM controls only the ignition timing and

dwell only. The DIS coils do the actual firing of the

spark plugs.

Conventional ignition coils have one end of the

secondary winding connected to earth. In the Direct

Ignition System, neither end of the secondary

winding is earthed. Instead, each end of a coil's

secondary winding is attached to a spark plug.

Thes e two plugs are on "c ompanion" c ylinders, i.e.,

on top dead centre at the same time.

When the coil discharges, both plugs fire at the

same time to complete the series circuit. The

cylinder on compression is said to be the `event'

cylinder and the one on exhaust is the `waste'

cylinder. The cylinder on the exhaust stroke

requires ver y little of the available energy to fir e the

spark plug at idle. The remaining energy will be

used as required by the cylinder on the

compression stroke. This method of ignition is

called "waste spark" ignition.

Since the polarity of the ignition coil primary and

secondary windings is f ixed, one spark plug always

fires with a forward current flow and it's

`companion' plug fires with a reverse current flow.

This is dif fer ent fr om a conventional ignition system

that fires all the plugs with the same direction of

current flow.

Figure 6C1-1-112 DIS Module And Coils

Since it requires approximately 30% more voltage

to fire a spark plug with reverse current flow, the

ignition coil design is im proved, with saturation tim e

and primary current flow increased. This redesign

of the system allows higher secondary voltage to

be available from the ignition c oils - greater than 40

kilovolts (40,000 volts) at any engine RPM. The

voltage required by each spark plug is determined

by the polarity and the cylinder pressure. The

cylinder on compression requires more voltage to

fire the spark plug (approximately 8 kilovolts) than

the one on exhaust (approximately 3 kilovolts).

It is possible f or one spark plug to fire even though

a plug wire fed by the same coil may be

disconnected from it's 'companion' spark plug. The

disconnected plug wire acts as one plate of a

capacitor, with the engine being the other plate.

These two 'capacitor plates' are charged as a spark

jumps across the gap of the still-connected spark

plug. The `plates' are then discharged as the

secondary energy is dissipated in an oscillating

current across the gap of the still-connected spark

plug. Secondary voltage requirements ar e very high

with an 'open' spark plug or wire. The ignition coil

has enough reserve energy to fire the still-

connected plug at idle, but possibly not under high

engine load. A more noticeable misfire may be

evident under load; both spark plugs may be

misfiring.

Figure 6C1-1-113 Waste Spark Ignition, Companion

Cylinders

SYSTEM COMPONENTS

CRANKSHAFT SENSOR CRANKSHAFT BALANCER INTERRUPTER RINGS

The dual crankshaft sensor, secured in an

aluminium mounting brack et and bolted to the front

left side of the engine timing c hain c over, is par tially

behind the crankshaft balancer. A 4-wire electrical

harness connector plugs into the sensor,

connecting it to the DIS module.

The DIS dual crankshaft sensor contains two Hall-

effect switches with one shared magnet mounted

between them. The magnet and each Hall switch

are separated by an air gap.

A Hall switch reacts like a solid-state switch,

earthing a low-current signal voltage when a

magnetic field is present. When the magnetic field

is shielded from the switch by a piece of steel

placed in the air gap between the magnet and the

switch, the signal voltage is not earthed. If the piece

of steel (called an interrupter) is repeatedly moved

in and out of the air gap, the signal voltage will

appear to go "ON-OFF-ON-OFF-ON-OFF."

Compar ed to a c onventional mec hanical dis tr ibutor,

this "ON-OFF" signal is similar to the signal that a

set of breaker points in the distributor would

generate as the distributor shaft turned and the

points opened & closed.

Figure 6C1-1-114 Crankshaft Sensor

In the case of the DIS system, the piece of steel is

two concentric interr upter rings m ounted to the rear

of the crankshaft balancer. Each interrupter ring

has blades and windows that, with crankshaft

rotation, either block the magnetic f ield or allow it to

reach one of the Hall switches. The outer Hall

switch is called the 18X crankshaft sensor,

because the outer interrupter ring has 18 evenly

spaced same-width blades and windows. The 18X

crankshaft sensor produces 18 "ON-OFF" earth

pulses per crankshaft revolution. The Hall switch

closest to the c rankshaf t, the 3X crank s haft sens or,

is so called because the inside interrupter ring has

3 unevenly-spaced, different-width blades and

windows. The 3X crankshaft sensor produces 3

different length "ON-OFF" earth pulses per

crankshaft revolution.

W hen a 3X inter rupter ring 'window' is between the

magnet and inner switch, the magnetic field will

cause the 3X Hall switch to earth the 3X c rank shaf t

signal voltage supplied from the DIS module. The

18X interrupter ring and Hall switch react similarly.

The DIS module interprets the 18X and 3X "ON-

OFF" signals as an indication of crankshaft

position, and must have both signals to "fire" the

correct ignition coil. The DIS module determines

crankshaft position for correct ignition coil

sequencing by counting how many 18X signal

transitions occur, i.e. "ON-OFF" or "OFF-ON,"

during a 3X pulse.

Figure 6C1-1-115 Crankshaft Balancer with Interrupter

Rings

Figure 6C1-1-116 18X and 3X Crankshaft Sensor Pulses for One Crankshaft Revolution

Figure 6C1-1-117 18X & 3X Crankshaft Sensor Pulses AND Crankshaft Reference Signal sent to the PCM

IGNITION COILS

Three twin-tower ignition coils are individually

mounted to the DIS module, with six screw type

fasteners. Each coil provides the spark for two

spark plugs simultaneously (waste spark

distribution), and all three coils can be replaced

individually. Spade type electrical term inals c onnect

each coil to the DIS module. Three of the six

terminals are connected together by a circuit in the

DIS module, supplying +12 volts to the primary

windings of all three coils. The other three terminals

are individually connected to the DIS module, so

that the DIS module can control only one coil firing

at a time, in the correct order, by removing the

primary circuit earth path at the proper time.

Figure 6C1-1-118 Ignition Coils & Ignition Module

DIS IGNITION MODULE

The DIS module serves several functions:

• It powers the dual crankshaft sensor internal

circuits.

• It supplies the 3X and 18X voltage signals that

each respective Hall switch pulses to earth to

generate the 3X and 18X crankshaft sensor

pulses.

• It determines the correct ignition coil firing

sequence, based on how many 18X transitions

occur during a 3X pulse. This coil sequencing

occurs at start-up. After the engine is running,

the module remembers the sequence, and

triggers the proper ignition coil.

• It sends a "crankshaft reference" signal to the

PCM. The PCM interpr ets engine RPM f rom this

signal. It is also used by the PCM to determine

crankshaft position for EST spark advance

calculations. (The falling edge of each

crankshaft reference signal pulse occurs 75

degrees before TDC of any cylinder.) The

crankshaft reference signal sent to the PCM by

the DIS module is an "on-off" pulse occurring 3

times per crankshaft revolution. This is neither

the 3X nor the 18X crank shaft sensor pulse, but

both of these are required by the DIS module to

generate the crankshaft reference signal.

• The DIS module generates the crankshaft

reference signal by an internal "divide-by-6"

circuit. This divider circuit divides the 18X

crankshaft sensor pulses by 6. The divider

circuit is enabled, or r eady to begin dividing, only

after it receives 3X crankshaft sensor pulses.

After it receives the first 3X crankshaft sensor

signal, the divider circuit does not need the 3X

pulses to continue operating. If either the 18X or

3X pulses are missing, the divider cannot

generate any crank shaft ref erence signal pulses

(sent to the PCM), and no fuel injector pulses

will occur.

• Below 450 engine RPM (or anytime the PCM

does not apply 5 volts to the DIS module

'bypass ' c irc uit), the DIS module c ontr ols ignition

by triggering eac h of the thr ee coils in the pr oper

sequence at a predetermined dwell, with spark

advance fixed at 10 degrees BTDC. This is

called bypass mode ignition. The DIS module

provides proper ignition coil sequencing during

both the module and EST modes.

• Above 450 RPM, the PCM applies 5 volts to the

DIS module 'bypass' circuit, signalling the

module to allow the PCM to control the dwell

and spark timing. This is EST mode ignition.

During EST mode, the PCM adjusts spark dwell

and timing advance for all driving conditions.

Again, the DIS module is responsible for proper

ignition coil sequencing during both the module

and EST modes.

Figure 6C1-1-119 Computer Controlled Coil Ignition

DIRECT IGNITION SYSTEM (DIS) NOTEWORTHY INFORMATION

There are important considerations to point out

when servicing the Direct Ignition System. This

"Noteworthy Information" will list some of these, to

help the technician in servicing the DIS system.

A. The ignition coils secondary voltage output

capabilities are very high - more than 40,000

volts. Avoid body contact with DIS high

voltage secondary components when the

engine is running, or personal injury may

result!

B. The dual Hall-effect 18X - 3X crankshaft

sensor is the most critical part of the DIS

system. If the crankshaft sensor is damaged

so that the 18X or 3X crankshaft sensor pulses

are not generated, the engine will not start!

C. There are 4 circuit wires connecting the dual

crankshaft sensor to the DIS module. If there

is a problem with any of the four, the engine

will not start (No s park and no inj ector pulses ).

The circuits are:

• +10-to-12 volt operating power supply for

the Hall switches from the DIS module.

• 18X sensor pulse signal to the DIS module.

• 3X sensor pulse signal to the DIS module.

• Earth circuit for both Hall switches.

• Equally important (for the engine to run) is

the crankshaft reference signal generated

by the DIS module, sent to the PCM. If the

PCM does not receive this signal, it will not

pulse the fuel injectors.

D. If the 3X c rank shaf t sensor pulses ceas e while

the engine is running, the engine will stop

running and will not restart.

E. If the 18X crankshaft sensor pulses cease

while the engine is running, the engine will stop

running and will not restart.

F. The crankshaft sensor is not adjustable in its

aluminium mounting bracket.

G. Ignition timing is not adjustable. Clearance

of the crankshaft sensor is only for proper

clearance of the r otating interr upter r ings in the

sensor air gap, and does not affect ignition

timing. There are no timing marks on the

crankshaft balancer or timing chain cover.

H If crank s haft s ensor replac em ent is nec essary,

the crank shaf t balancer m us t be rem oved firs t.

The balancer is a press fit onto the crank shaft

and must be removed with a special tool;

removing the serpentine accessory drive belt,

balancer and crankshaft sensor shield will

allow access to replacing the crankshaft

sensor. When reinstalled, the proper torquing

of the balancer attachment bolt is critical to

ensure the balancer stays attached to the

crankshaft.

IIf a crankshaft sensor assembly is

replaced, 2 items are very important:

1. Check the crankshaft balancer interrupter

rings for any blades being bent (runout and

concentric ity). If this is not checked c losely and

a bent blade exists, a new crankshaft sensor

can be destroyed by the bent blade with only

one revolution of the crankshaft!

2. The proper crankshaft sensor replacement

procedure must be followed. Refer to

Section 6C1-3 SERVICE OPERATIONS for

proper replacem ent proc edure. T his proc edure

will position the interrupter rings in the centre

of the sensor air gaps.

J. Neither side of the ignition coil primary or

secondary windings is connected to engine

earth.

K. Be careful not to damage the high tension

leads or boots (dust caps) when servicing the

ignition system. Rotate each boot to dis lodge it

from the plug or coil tower before pulling it

from either a spark plug or the ignition coil.

Never pierce a high tension lead or boot for

any testing purposes! Future problems are

guaranteed if pinpoints or test lights are

pushed through the insulation for testing.

L The DIS m odule is earthed to the engine bloc k

through 2 mounting studs used to secure the

module to it's mounting bracket. If servicing is

required, ensure that good electrical contact is

made between the module and its mounting

bracket, including proper hardware & torque.

M A conventional tachometer used to check RPM

on a primary ignition 'tacho lead' will not work

on DIS. To check RPM, use one of the

following methods:

• A tachometer designed with an inductive

pickup, used on the secondary side of an

ignition system.

• These tachometers are identified by a

'clamp' that goes around a spark plug wire.

Set the tacho to '2-cycle' operation. The

reason for 2- cycle? Spark plugs on this

engine fire every time the piston is at the

top of it's stroke. If a '2 cycle' selection is

not available, divide the indicated 4 cycle

reading by 2.

• Tech 2 scan tool. Use "Engine Speed"

display to read actual RPM.

1.8 ELECTRONIC SPARK TIMING (EST)

The V6 Direct Ignition System uses the same four

ignition module to PCM circuits as do all other

Delco engine management systems. They are:

• Crankshaft Reference PCM Input

• Crankshaft Reference Earth

• Bypass Control

• EST Output

Electronic Spark Timing is the PCM's method of

controlling spark advance and ignitions dwell, when

the ignition system is operating in the EST mode.

There are two "modes" of ignition system operation:

• Bypass mode

• EST mode

In the bypass mode, the ignition system operates

independently of the PCM, with bypass mode s park

advance always at 10 degrees BTDC. The bypass

mode is in effect when cranking the engine. The

PCM has no control of the ignition system when in

this mode. In fact, the PCM could be disconnected

and removed from the car and the ignition system

would still fire the spark plugs while cranking, as

long as the other ignition system com ponents were

functioning! (This would provide spark but no fuel

injector pulses, and a no-start.)

After the engine starts (RPM greater than 450), the

PCM will cause the ignition system to change over

to the EST mode. On ce the c hange is made to EST

mode, it will stay in effect until either:

1. The ignition key is turned "OFF",

2. The engine quits running, or

3. An EST fault is detected.

If an EST fault is detected while the engine is

running, the ignition system will switch back to the

bypass m ode. The engine m ay quit running, but will

restart and stay in the bypass mode.

Figure 6C1-1-120 Cranking Below 450 RPM

Figure 6C1-1-121 Engine Running Above 450 RPM

In the EST mode, the ignition spark timing and

ignition dwell time is fully controlled by the PCM.

EST spark advance and ignition dwell is calculated

by the PCM using the following inputs:

• Engine speed (crankshaft reference)

• Crankshaft position (crankshaft reference)

• Engine load (MAF)

• Engine coolant temperature (ECT)

• Throttle position (TP sensor)

• Park/neutral (TFP)

• Detonation (Knock sensor)

• Vehicle speed (VSS)

• Diagnostic request input - (DLC diagnostic test"

terminal)

• PCM supply voltage

The following describes the four PCM-to-ignition

module circuits.

Figure 6C1-1-122 Engine Running with EST Inputs

CRANKSHAFT REFERENCE PCM INPUT

From the ignition module, the PCM uses this signal to calculate engine RPM and crankshaft position. The PCM

compares pulses on this circuit to any that are on earth crankshaft reference low circuit. The PCM also uses the pulses

on this circuit to initiate injector pulses. If the PCM receives no pulses on this circuit, no fuel injection pulses will occur,

the engine will not run, and DTC 46 will set when attempting to start the engine.

CRANKSHAFT REFERENCE EARTH

This is an earth circuit for the digital RPM counter inside the PCM, but the wire is connected to engine earth only

through the ignition module. Although this circuit is electrically connected to the PCM, it is not connected to earth at or

through the PCM. The PCM compares voltage pulses on the reference input circuit to any on this circuit. If the circuit is

open, or connected to earth at the PCM, it may cause poor engine performance and possibly a "Check Powertrain"

Lamp with no DTC.

BYPASS CONTROL

The PCM either allows the ignition module to keep the spark advance at "bypass mode" 10 degrees BTDC, or the PCM

signals the ignition module that the PCM is going to control the spark advance (EST mode). The ignition module

switches between the two modes by the level of voltage that the PCM sends to the ignition module on the bypass

control circuit. The PCM provides 5 volts to the ignition module if the PCM is going to control spark timing (EST mode).

If the PCM does not turn "ON" the 5 volts, or if the ignition module doesn't receive it, then the module will keep control

of spark timing (bypass mode). An open or earthed bypass control circuit will set a DTC 42 and the ignition system will

stay in 'bypass mode'. If the bypass control circuit is shorted to voltage then DTC 41 will set.

EST OUTPUT

The EST output circuitry of the PCM sends out timing pulses to the ignition module on this circuit. When in the "bypass

mode," the ignition module earths these pulses. When in the EST mode, these pulses are the ignition timing pulses

used by the ignition module to energise the ignition coil. If the EST output circuit is open when the engine is started, a

DTC 41 will set and the ignition system will stay in the bypass mode. If this circuit becomes shorted to voltage or

earthed during EST mode operation above 1600 RPM, then DTC 42 will set.

HOW DTC 41 AND DTC 42 ARE DETERMINED

The EST output circuitry in the PCM issues EST output pulses anytime crankshaft reference signal input pulses are

being received. When the ignition system is operating in the bypass mode (no voltage on the bypass control circuit), the

ignition module earths the EST pulses sent from the PCM. The ignition module will remove the earth path for the EST

pulses only after switching to the EST mode. (The PCM commands the switching between bypass & EST modes, via

applying 5 volts on the bypass control circuit to the ignition module.)

The PCM has voltage monitors on the EST output line and the bypass control line. The PCM monitors it's EST output,

and expects to detect no EST pulses on the EST circuit when it has not supplied the 5 volts on the bypass control

circuit. When the RPM for EST operation is reached (approximately 450 RPM), the PCM applies 5 volts to the bypass

control circuit, and the EST pulses should no longer be earthed by the ignition module. The PCM constantly monitors

it's EST output, and should 'detect' the high EST pulses only when in the 'EST mode.'

If EST output circuit is open, the PCM will detect EST output pulses while attempting to start the engine (in the

bypass mode) due to the ignition module not being able to earth the EST pulses. The PCM will check for this condition

during engine cranking. Three things will occur: 1. A DTC 41 will set, 2. The PCM will not apply 5 volts to the bypass

control circuit, and 3. The engine will start and run in the bypass mode.

If EST output circuit is e arthed or shorted to voltage, the PCM would not detect a problem until the change to EST

mode happens. When the PCM applies 5 volts to the bypass control circuit, the ignition module will switch to the EST

mode. With EST circuit earthed or shorted to voltage, there would be no EST pulses for the ignition module to trigger

the ignition coil with, and the engine may falter. The PCM will quickly revert back to the bypass mode (turn "OFF" the 5

volts on the bypass control circuit), DTC 42 will set, after the engine speed exceeds 1600 RPM. The ignition system will

operate in the bypass mode until the fault is corrected and the engine is stopped and restarted.

If bypass control circuit is open OR earthed, the ignition module can not switch to the EST mode. In this case, the

EST pulses will stay earthed by the ignition module, and DTC 42 will be set after the engine speed exceeds 1600 RPM.

The engine will start and run in the bypass mode.

If bypass control circuit is shorted to voltage, the ignition module will be switched to the EST mode all the time. In

this case, the PCM would detect voltage on the bypass circuit only with the engine cranking and set DTC 41. The

engine would start and run in the EST mode.

RESULTS OF INCORRECT OPERATION

An open or earth in the EST or bypass circuit will set a DTC 41 or DTC 42. If a fault occurs in the EST output circuit

when the engine is running, the engine may falter or quit running but will restart and run in the bypass mode. A fault in

either circuit will force the ignition system to operate on bypass mode timing (10 degrees BTDC), which will result in

reduced performance and fuel economy.

The PCM uses information from the MAF and coolant temperature sensors in addition to RPM to calculate the main

spark advance values as follows:

High RPM = more advance

Low MAF frequency

(Low engine load) = more advance

Cold engine = more advance

Low RPM = less advance

High MAF frequency

(High engine load) = less advance

Hot engine = less advance

Therefore, detonation could be caused by incorrect low MAF output frequency or incorrect high resistance in the coolant

temperature sensor circuit. Poor performance could be caused by incorrect high MAF output frequency or incorrect low

resistance in the coolant temperature sensor circuit.

1.9 ELECTRONIC SPARK CONTROL (ESC) SYSTEM

PURPOSE

Varying octane levels in today's petrol may cause

detonation in some engines. Detonation is caused

by an uncontrolled pressure in the combustion

cham ber . This uncontrolled pr es sur e c ould produc e

a flam e f r ont oppos ite that of the normal flam e f r ont

produced by the spark plug.

The "rattling" sound normally associated with

detonation is the result of two or more opposing

pressures (flame fronts) colliding within the

combustion chamber. Though "light" detonation is

sometimes considered normal, "heavy" detonation

could result in engine damage. Light detonation

occurs when the point of maximum pressure has

been exceeded.

To control spark knock, a Knock Sensor (KS) is

used. This system is designed to retard spark

timing up to 15 degrees to reduce spark knock in

the engine. This allows the engine to use max imum

spark advance to improve driveability and fuel

economy.

OPERATION

The ESC system has two major components:

• Knock Sensor Module (part of PCM)

• Knock Sensors

Figure 6C1-1-123 Knock Sensor

The knock sensor detects abnormal mechanical

vibration (spark knocking) in the engine. There are

several calibrations of knock sensors because

each engine produces a different frequency of

mechanical noise. The knock sensor is specifically

chosen f or this engine to best detect engine knock ,

over all the other noises in the engine. T his engine

has two knock sens ors. Each sensor is mounted in

the engine block near each bank of cylinders to

better detect detonation.

Figure 6C1-1-124 Knock Sensor Locations

Figure 6C1-1-125 Knock Sensor Wiring

Under a no knock condition, the circuit should

measure about 32 mV AC. The knock sensor

produces an AC output voltage that increases with

the severity of the knoc k. T his signal voltage inputs

to the PCM. This AC signal voltage to the PCM is

processed by an analog signal to a Signal Noise

Enhancement Filter (SNEF) module. This SNEF

module is used to determine if the AC signal

com ing in is noise or actual detonation. This SNEF

module is part of the PCM and cannot be replaced.

The processed knock sensor signal is then

supplied to the PCM. The PCM then adjusts the

ignition control system to reduce the spark

advance. How much the tim ing is retarded is based

upon the amount of time knock is detected and is

limited to a maximum value of 15 degrees. After

the detonation stops, the tim ing will gradually return

to it's calibrated value of spark advance. The Knock

Sensor system will only retard timing after the

following conditions are met:

• Engine running longer than 5 seconds

• Battery voltage higher than 9.3 volts

• Engine speed above 550 RPM

• ECT greater than 45 degrees C

Figure 6C1-1-126 Knock Sensor Sectioned View

The Tech 2 scan tool has two data displays to

check for diagnosing this knock sensor circuit.

"KNOCK SIGNAL" is used to monitor the input

signal from the knock sensor. This position will

display "YES" when knock is being detected.

"KNOCK RETARD" is the indication of how much

the PCM is retarding the spark advance.

The Knock Sens or System has two DT C's to detec t

a failure in its system. DTC 43 is designed to

diagnose the knock sensor and wiring, so that

problems encountered with this circuit should set

the DTC. The PCM learns a minimum noise level

from the knock sensors.

• The actual noise level is determined as: Noise

level = Filtered noise - minimum noise

If the noise level is too low or too high then DTC 43

will be set.

The second DTC associated with the Knock

Sensor is DTC 93. DTC 93 indicates that the

engine has been detonating longer than normal.

The PCM monitors the output of the SNEF circuit.

When the SNEF output signal is s ignificantly longer

than the longest expected "normal": output it is

assumed that the SNEF circuitry has failed and

DTC 93 is set.

1.10 EVAPORATIVE EMISSION

The Evaporative Emission Control System (EECS)

used on this vehicle is the charcoal canister

storage method. T his method tr ansfers f uel vapour

from the fuel tank to an activated car bon (charcoal)

storage device (canister located under the rear of

the vehicle) to hold the vapours when the vehicle is

not operating. When the engine is running, the f uel

vapour is purged from the carbon 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

W idth Modulated (PWM) or tur ned “ON” and “OF F”

several tim es a sec ond. T he PCM controlled PWM

output is commanded when the appropriate

conditions have been met:

• Engine coolant temperature above 80°C.

• Engine has been running longer than 3

minutes.

• Engine is not in Decel Fuel Cutoff Mode.

• Throttle opening is less than 92%.

• Engine is in Closed Loop mode.

Figure 6C1-1-127 Fuel Vapour Canister

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 92%.

The canister (located under the rear 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 the vehicle

Series Owners Handbook.

Figure 6C1-1-128 Canister Purge Solenoid Location

Figure 6C1-1-129 Canister Purge Solenoid Circuit

The fuel vapour canister is mounted in a bracket

underneath the vehicle, located by the fuel filter.

This canister is a three port design. T he f uel vapour

is absorbed by the charcoal within the canister.

When the engine is running at idle speed and

above idle, air is drawn into the canister through the

atmospheric port at the top of the canister

assembly. The air mixes with the fuel vapour and

the mix tur e is dr awn into the intak e manif old via the

canister purge line. Upperm ost port on the canister

is controlled by a PCM controlled canister purge

solenoid. The canister purge solenoid controls the

manif old vacuum signal from the throttle body. The

port below the canister purge port is the vapour

inlet from the fuel tank . The single of f centre por t is

open to the atmosphere.

Figure 6C1-1-130 Canister Location

RESULTS OF INCORRECT OPERATION

Poor idle, stalling and poor driveability can be

caused by:

• Inoperative canister purge solenoid

• Damaged canister.

• Hoses split, crac ked and/or not c onnec ted to the

proper tubes.

Evidence of fuel loss or fuel vapour odour can be

caused by:

• Liquid fuel leaking from fuel lines.

• Cracked or damaged canister.

• Disconnected, misrouted, kinked, deteriorated

or damaged vapour hoses, or control hoses.

If the solenoid is stuck open, or the control circ uit is

shorted to earth the canister will purge to the intak e

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 97.

Figure 6C1-1-131 Sectioned View of Canister

Figure 6C1-1-132 Typical Evaporative Emission Control Schematic

1.11 ELECTRIC COOLING FAN

Figure 6C1-1-133 Cooling Fan Circuit

The V6 engine has two, two speed electric engine

cooling fan assembly that provides the primary

means of moving air through the engine radiator.

The two, two speed electric cooling fan are us ed to

cool engine coolant flowing through the radiator.

The two, two speed electric cooling fans are also

used to cool the ref rigerant flowing through the A/C

condenser (if fitted).

The each engine cooling fan motor has four

terminals, two negative and two positive terminals.

The two negative terminals are the relay controlled

circuits for fan operation. T he two positive term inals

are the direct power feed from a fusible link to the

fan motors. When a earth signal is applied to one of

the negative terminals, the fan motor will operate at

low speed. When a earth signal is applied to both

negative terminals, both fan will operate at high

speed.

The engine cooling fan high speed relay is

controlled by the PCM. T he PCM controls the earth

path for the engine cooling fan high speed relay.

The low speed of the electric fan is controlled by

the PCM through a special Data Com munication to

the BCM. The BCM controls the earth path for the

engine cooling fan low speed relay. The engine

cooling fan high speed relay and the engine

cooling fan low speed relay are used to contr ol the

earth signal to the electr ic mo tor that drives the f ive

bladed fan.

The PCM determines operation of the two, two

speed engine cooling fan based on A/C request,

engine coolant temperature, A/C Refrigerant

Pressure Sensor, 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 speak ers. Is shorted to earth, the

fan motors could continuously run, or the fuse or

fusible link could fail.

Figure 6C1-1-134 Engine Cooling Fan Assembly

ENGINE COOLING FAN LOW SPEED

The engine cooling fan low speed relay is

energised by the BCM. The PCM determ ines 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 request indicated (YES) and either the

vehicle speed is less than 30 km/h

- OR -

• A/C pressure is greater than 1500 kPa

- OR -

• The coolant temperature is greater than 104

degrees C.

If the coolant temperature is greater than 117

degrees C when the ignition is switched off, the

relay is energised for up to approximately 4

minutes.

If an engine coolant temperature sensor fault is

detected, such as DTC 14, 15, 16, 17 or 91.

The cooling fan low speed relay will be turned

"OFF'' when any of the following conditions have

been met:

• The A/C request is not indicated (NO)

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

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

pressure is less than 1170 kPa.

Figure 6C1-1-135 Cooling Fan Low Speed Relay Location

ENGINE COOLING FAN HIGH SPEED

The engine c ooling f an high s peed relay is controlled by the PCM based on input from the Engine Coolant Tem per atur e

(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 conditions are satisfied.

There is a BCM message response fault which will cause a DTC 92

An engine coolant temperature sensor fault is detected such as DTC 14,15,16,17.

Coolant temperature greater than 104 degrees C.

The engine cooling fan high speed relay can also be enabled by the A/C Refrigerant Pressure Sensor. W hen the A/C

Refrigerant Pressure Sensor determines the A/C system pressure is to high, greater than 2600 kPa, and this will

instruct the PCM to enable the high speed fan.

If the low speed f an was "OF F" when the cr iteria was met to tur n the high speed fan "ON", the high s peed f an will come

"ON" 5 seconds after the low speed fan is turned "ON". " If both the engine cooling fan relays are "ON", the PCM will

turn "OFF" the high speed relay when:

The engine coolant temperature is less than 99 degrees C.

A/C request not indicated (NO)

A/C request indicated (YES) and A/C pressure is less than 2300 kPa.

1.12 A/C CLUTCH CONTROL

A/C CLUTCH CONTROL WITH ECC

Figure 6C1-1-136 A/C Clutch Control With ECC

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

One type is standard A/C (Figure 6C1-1-139) and

the other uses a Electronic Climate Control (ECC)

module (Figure 6C1- 1-136).

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

the Electronic Climate Control Module will supply a

signal to the BCM. The BCM will then send a serial

data request to the PCM. W hen the PCM receives

the serial data request on PCM terminal B12, 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 adjust the idle speed before turning "ON"

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

available to the PCM, the A/C compressor will be

inoperative.

If there is a problem with the PCM A/C Relay

Control circuit, QDSM DTC 91 will set.

The BCM also supplies the earth signal from BCM

terminal "7" to the low speed cooling fan relay.

This A/C system also incorporates a A/C

Refrigerant Pressure Sensor. The A/C Refrigerant

Pressure Sensor signal indicates high side

refrigerant pressure to the PCM. The PCM uses

this infor mation to adj ust the idle air c ontrol valve to

compensate for the higher engine loads present

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

A/C Refrigerant Pressure Sensor signal will cause

DTC 96 to set.

Figure 6C1-1-137 A/C Refrigerant Pressure Sensor

Location

The PCM will NOT energise the A/C control

relay if any of the following conditions are

present:

• RPM more than 5,800. If de-energised because

of RPM, it can re-energised when RPM falls

below 5,400.

• Throttle is more than 99% open. When de-

energised during wide-open throttle, it will be re-

energised when the throttle is less than 93%

open.

On vehicles equipped with non-ECC systems the

power flow is different. With the blower fan

switched "ON", and the air conditioning switched

"ON," switched ignition voltage is supplied from

fuse F13 through the A/C master switch, and then

to the BCM. The BCM will then supply a serial data

signal to the PCM requesting A/C. If the BCM does

not receive a earth s ignal 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 pres sor relay. T he BCM also supplies the ear th

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 compressor will be inoperative.

This system like on the ECC system also

incorporates a A/C Refrigerant Pressure Sensor.

The A/C Refrigerant Pressure Sensor signal

indicates high side r ef riger ant pr ess ur e to the PCM.

The PCM us es this inf orm ation to adj ust 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 Sensor

signal will cause DTC 96 to set.

Figure 6C1-1-138 A/C Relay Location

A/C CLUTCH CONTROL WITHOUT ECC

Figure 6C1-1-139 A/C Clutch Control Without ECC

1.13 S UP ERCHARGER SYSTEM

DESCRIPTION

The supercharger is a positive displacement pump that consists of two counter-rotating rotors in a housing with an inlet

port and an outlet port. The rotors are designed with three lobes and a helical twist. An air bypass circuit is built into the

housing. The rotors in the supercharger are designed to run at a minimal clearance, not in contact with each other or

the housing. The rotors ate timed to each other by a pair of precision spur gears which are pressed onto the rotor

shafts. The forward end of the rotors are held in position by deep groove ball bearings. The back end of the rotors are

supported by sealed roller bearings.

The gears and ball bearings are lubricated by a sy nthetic oil. The oil reservoir is self-contained in the supercharger and

does not rely on engine oil for lubrication.

The cover on the supercharger contains the input shaft which is supported by two deep groove ball bearings and is

coupled to the rotor drive gears. The pulley is pressed and keyed onto the input shaft. These bearings are lubricated by

the synthetic oil contained in the same reservoir as the gears and rotor bearings.

SUPERCHARGER OPERATION

The supercharger is designed to pump more air than the engine would normally use. This excess air creates a boost

pressure in the intake manifold. Maximum boost can range from 50 to 80 kPa (7 to 11 P.S.I.). Since the supercharger is

a positive displacement pump and is directly driven from the engine accessory drive system, boost pressure is available

at all driving conditions.

When boost is not desired, such as during idle and light throttle cruising, the excess air that the supercharger is

producing is routed through the bypass passage between the intake manifold and the supercharger inlet. This bypass

circuits regulated by a bypass valve which is similar to a throttle plate. The bypass valve is controlled by a vacuum

actuator which is connected to the vacuum signal between the throttle and the supercharger inlet. Spring force from the

actuator holds the valve closed to create boost and vacuum pulls the valve open when the throttle closes to decrease

boost. The open bypass valve reduces pumping loss thereby increasing fuel efficiency.

The Boost Control Solenoid valve is an electronically controlled valve. This valve, controlled by the PCM, determines

whether pressure from the manifold is routed to the bypass actuator or closed off. The solenoid allows pressure from

the manifold to open the bypass valve and regulate boost pressure during specific driving conditions.

BOOST CONTROL

The boost control system regulates induction boost pressure during rapid deceleration, under very high engine load

situations and anytime reverse gear is selected.

Figure 6C1-1-140 Supercharger Components

OPERATION

Under most conditions, the PCM commands the

Boost Control Solenoid to operate at 100% duty

cycle ("ON"), keeping the solenoid valve closed and

allowing only inlet vacuum to control the position of

the Bypass valve. At idle, full inlet vacuum is

applied to one side of the Bypass Valve Actuator

diaphragm counteracts spring tension to hold the

bypass valve open. As the engine load increases,

reduced vacuum acts upon the spring tension in

the Bypass Valve Actuator, causing the bypass

valve to close and increasing boost pressure.

W hen reduced boost pressure is desired, the PCM

commands the Boost Control Solenoid to operate

at 0% duty cycle ("OFF"). This opens the solenoid

valve and allows boost pressure from the intake

manifold to counteract the spring tension in the

Bypass Valve Actuator, opening the bypass valve

and recirculation excess boost pressure back into

the supercharger inlet. W ith reverse gear selected,

the PCM commands the Boost Control Solenoid to

operate at 0% duty cycle ("OFF") at all times. Figure 6C1-1-141 Bypass Valve Actuator

RESULTS OF INCORRECT OPERATION

An open Boost Control Solenoid driver circuit, ignition feed circuit, or Boost Control Solenoid valve stuck open will cause

reduced engine power, especially during wide open throttle operation.

The Boost Control Solenoid driver circuit shorted to earth, Boost Control Solenoid valve stuck closed or a restriction in

the boost source or signal hoses will cause full boost to be commanded at all times and a possible overboost condition

during high engine load situations.

A restriction in the vacuum signal hoses to the Bypass Valve Actuator or a stuck closed bypass valve will cause a rough

idle and reduced fuel economy.

DIAGNOSIS

The boost control system diagnosis is covered in Chart 2-11. For further information on the Supercharger and boost

control system, and on vehicle service, refer to 3.24 SUPERCHARGER SYSTEM.

Figure 6C1-1-142 Boost Control Solenoid Location

Figure 6C1-1-143 Boost Control System (Bypass Closed)

Figure 6C1-1-144 Boost Control System (Bypass Open)

1.14 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 and Anti-Lock Brake (ABS) system.

The ABS/ET C module m onitors both front and rear

wheel speeds through the wheel speed sensors. If

at any time during acceleration the ABS/ETC

module detects drive wheel slip, it will request (on

the Torque Request circuit) the Powertrain Control

Module (PCM) to bring exc ess engine torque into a

specific range. This is accomplished via two high

speed Pulse Width Modulated (PWM) circuits

between the ABS/ETC module and the PCM. This

is displayed on the scan tool as a Nm number. T he

PCM will then adjust spark firing and air/fuel ratio,

altering boost duty cycle (Supercharger only), and

shutting "OFF" up to five (5) injectors (if

necessary), and report the modified torque value

(on the Torque Achieved circuit) back to the

ABS/ETC module in the form of a Nm number.

These Nm numbers should match closely when

traction control is being requested. Simultaneous

with engine torque management, the ABS/ETC

module will activate the ABS isolation valves, turn

on the ABS pump motor and s upply brak e pres s ure

to the over spinning wheel(s).

Figure 6C1-1-145 ABS/ETC Module Location

The isolation valves isolate the front brake

hydraulic circuits from the master 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 Brake mode is that brake fluid pressure

is increased to lesson 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

Control mode and allow manual braking.

If there is a malfunction with the Torque Request

PWM circuit between the ABS/ET C module and the

PCM, DTC 95 will set. If there is a malf unction with

the Torque Achieved circuit between the ABS/ET C

module and the PCM, a ABS/ECT DTC will set.

For further description on the Anti-Lock Brake

(ABS) system, and Electronic Traction Control

(ETC) system, refer to Section 12L ABS &

ABS/ETC for information on ABS/ETC operation

and DTC diagnosis.

1.15 ABBREVIATIONS AND GLOSSARY OF TERMS

Abbreviations used in this Volume are listed below in alphabetical order with an explanation of the abbreviation.

AC - ALTERNATING CURRENT - A current with varying magnitude.

A/C - AIR CONDITIONING

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

ANALOG SIGNAL - An electrical signal that varies in voltage within a given parameter.

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

BATTERY - Stores chemical energy and converts it into electrical energy. Provide DC current for the vehicles electrical

systems.

CAMSHAFT POSITION SENSOR - The PCM uses this signal to determine the position of the No.1 piston in its power

stroke. This signal is used by the PCM to calculate sequential fuel injection mode of operation.

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

and the muffler. It is the primary "workhorse" of the emission control sy stem, and the PCM's control of the air/fuel ratio

allows it to operate efficiently. It contains platinum, palladium and rhodium. It receives pollutants (HC, CO, and NOx)

emitted by the engine, and through a chemical reaction, converts these harmful pollutants into harmless water vapour,

carbon dioxide, and nitrogen. Maximum conversion efficiency of exhaust emissions is achieved with precise control of

the air/fuel ratio at 14.7-to-1.

CCP - CONVERTER CANISTER PURGE - A PCM controlled solenoid to purge the charcoal canister.

"CHECK POWERTRAIN" LAMP - Warning indicator with the outline of an engine. The "check powertrain lamp" is

located on the instrument panel, and is controlled by the PCM. "Check powertrain lamp" is illuminated by the PCM when

it detects a malfunction in the engine or transmission management system. "Check powertrain lamp" is on and when

the ignition is "ON" with the engine not running (bulb check).

CKT - CIRCUIT

CLOSED LOOP - A fuel control system mode of operation that uses the signal from the exhaust oxygen sensor, in

order to control the air/fuel ratio precisely at a 14.7 to 1 ratio, allowing maximum efficiency of the catalytic converter.

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

DC - DIRECT CURRENT - A current with a constant direction.

DTC - DIAGNOSTIC TROUBLE CODE - The PCM can detect malfunctions in the engine or transmission management

system. If a malfunction occurs, the PCM may turn on the "Check Powertrain" lamp, and a two-digit code number will

set in the PCM's memory. A diagnostic trouble code can be obtained from the PCM through the "Check Powertrain"

lamp, or with the Tech 2 scan tool. This DTC will indicate the area of the malfunction, and properly following the service

diagnostic procedures for the engine management system will locate the source of the problem.

NOTE:

DTC 12 is used to verify that the PCM's diagnostic ability is operational.

DIAGNOSTIC "TEST" ENABLE TERMINAL - A terminal of the Data Link Connector (DLC) earthed to obtain a

Diagnostic Trouble Code by flashing out the MIL "Check Powertrain Lamp".

DIGITAL SIGNAL - An electrical signal that is either one of two states, "ON" or "OFF" with no in between.

DLC - DATA LINK CONNECTOR - The 16 pin connector used at the assembly plant to evaluate the control module

system.

The connector is also used in service to flash the Malfunction Indicator Lamp (MIL) "Check Powertrain Lamp". This

connector is also used by the Tech 2 scan tool to make system checks.

DLC DATA STREAM - An output of the PCM, initiated by the Tech 2 scan tool sending a command to the PCM. This

output is a digital computer language signal, used by assembly plant test equipment and the Tech 2 scan tool. This

signal is transmitted to the data link connector.

DRIVER - An electronic device, usually a power transistor, that operates like a switch; that is, it turns something "ON" or

"OFF."

DUTY CYCLE - The measurement of the length of time, in percentage, that a circuit is "ON" versus "OFF" when

compared with a 100% full ON/OFF time factor.

DVM (10 Meg.) - Digital voltmeter with 10 million ohms per volt impedance - used for voltage and resistance

measurement in electrical/electronic systems.

EECS - EVAPORATIVE EMISSIONS CONTROL SYSTEM - Used to prevent petrol vapours in the fuel tank from

entering the atmosphere. Stores the vapours in a storage canister, located in the engine compartment. Canister

contains activated charcoal, and the vapours are "purged" by engine vacuum during certain operating conditions.

EEPROM - ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY - Ty pe of read only memory

(ROM) that can be electrically programmed, erased and reprogrammed.

EMI OR ELECTRICAL NOISE - An unwanted signal interfering with another needed signal; like an electric razor upsets

a television picture, or driving under high voltage power lines upsets the AM radio in a vehicle.

EGR - EXHAUST GAS RECIRCULATION VALVE - A device that is used to lower Oxides of Nitrogen (NOx) emission

levels by recalculating exhaust gases back into the combustion chamber.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR - Device that senses the engine coolant temperature, and

passes that information to the powertrain control module.

EPROM - ERASABLE PROGRAMMABLE READ ONLY MEMORY - Type of read only memory (ROM) that can be

erased with ultraviolet light and reprogrammed.

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

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 "test" enable terminal is earthed.

FUSE - A thin metal strip that melts through when excessive current flows through it, thereby stopping current flow and

protecting a circuit from damage.

HC - HYDROCARBONS - One of the pollutants found in engine exhaust.

HIGH - A voltage more than a specific threshold such as earth or 0. In digital signals, high is "ON" and low is "OFF".

HYSTERESIS - Movement that does not follow the same path as it entered an area as it exits.

IAC - IDLE AIR CONTROL - Installed in the throttle body unit and controlled by the PCM to regulate idle air flow, and

thus idle RPM.

IAT - INTAKE AIR TEMPERATURE SENSOR - Senses intake manifold incoming air temperature, and passes that

information to the PCM.

IDEAL MIXTURE - The air/fuel ratio that provides the best performance, while maintaining maximum conversion of

exhaust emissions, typically 14.7 to 1 on petrol 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 it's outputs.

INTERMITTENT - Occurs now and then; not continuously. In electrical circuits, refers to occasional open, short, or

earth.

I.C. - INSTRUMENT CLUSTER

LOW - A voltage less than a specific threshold. Operates the same as an earth and may, or may not, be connected to

chassis earth.

MAF - MASS AIR FLOW SENSOR - A device that monitors the amount of air flow coming in the engine intake. The

MAF sensor sends a signal to the PCM.

MODE - A particular state of operation.

N.C. - NORMALLY CLOSED - Switch contacts that are connected, or together, when no outside forces (temperature,

pressure, position) are applied.

N.O. - NORMALLY OPEN - Switch contacts that are not connected, or not together, when no outside forces

(temperature, pressure, position) are applied.

NOx - NITROGEN OXIDES - One of the pollutants found in engine exhaust.

O2 - OXYGEN

OXYGEN SENSOR - Exhaust gas oxygen sensor, fitted in the exhaust manifold. Senses leftover oxygen after the

combustion process, and produces a very small electrical signal based on the amount of oxygen in the exhaust gas, as

compared to oxygen in the atmosphere.

OPEN LOOP - Describes PCM control of the fuel control system without use of oxygen sensor information.

OUTPUT - Functions, typically solenoids and relays, that are controlled by the PCM.

PCM - POWERTRAIN CONTROL MODULE. A metal cased box (located in passenger compartment) containing

electronic circuitry that electrically monitors and controls the transmission system and emission systems of the engine

management system. It also turns "ON" the "Check Powertrain" lamp when a malfunction occurs in the sy stem.

PCV - POSITIVE CRANKCASE VENTILA TION - Method of reburning crankcase fumes, rather than passing them

directly into the atmosphere.

PFI - PORT FUEL INJECTION - Method of injecting fuel into the engine. Places a fuel injector at each inlet port of a

cylinder head, directly in front of the intake valve, mounted in the intake manifold.

PROM - PROGRAMMABLE READ ONLY MEMORY - an electronic term used to describe the engine calibration unit.

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

PULSE WIDTH MODULATED (PWM)- a digital signal turned "ON" and "OFF'" for a percentage of available on-plus-off

cycle time, such as 30% "on" and 70% "off" would be called a 30% "ON" PWM signal.

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

OFF" or pulse width modulated.

RAM - RANDOM ACCESS MEMORY - Is the microprocessors "scratch pad". The processor can write into, or read

from this memory as needed. This memory is volatile and needs a constant supply of voltage to be retained. If the

voltage is lost or removed, this memory is lost.

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

voltage signals are typically 5 volts (high) and 0 volts (low) and are transmitted through a wire often referred to as the

serial data line.

SEQUENTIAL FUEL INJECTION - A mode of injecting fuel into the engine on the intake stroke of each cylinder.

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

or ball to move.

SUPPRESSION CAPACITORS - These capacitors are connected between the power and earth circuits of the cooling

fan motors. These capacitors are for controlling fan motor noise in the radio.

SWITCH - Opens and closes circuits, thereby stopping or allowing current flow.

TCC - TORQUE CONVERTER CLUTCH - PCM controlled solenoid in automatic transmission that positively couples

the transmission input shaft to the engine.

TECH 2 SCAN TOOL - A hand-held diagnostic tool, containing a microprocessor to interpret the PCM's DLC data

stream. A display panel displays the PCM input signals and output commands.

TP SENSOR - THROTTLE POSITION SENSOR - Device that tells the PCM the current throttle position, and, when it is

moving, the rate of throttle opening / closing.

VACUUM, MANIFOLD - Vacuum source in the engine.

VACUUM, PORTED - Vacuum soured from a small "port" in the throttle body. With the throttle closed, there would be

no vacuum measured, because the port is on the air cleaner side of the throttle blade, and is exposed to engine

vacuum only after the throttle is open.

VSS - VEHICLE SPEED SENDER (Vehicles with Manual Transmission) - Pulse generator mounted in the

transmission. The speedometer circuitry contains an electronic divider circuit that sends a signal to the PCM and, if so

equipped, the body control module or trip computer.

VSS - VEHICLE SPEED SENSOR (Vehicles with Automatic Transmission) - A permanent magnet type sensor

which produces AC voltage which is sent to the PCM to determine vehicle speed.

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

electronic devices.

WOT - WIDE OPEN THROTTLE