Engine Management – V6 – General Information Page 6C1-1–1

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Section 6C1-1

Engine Management – V6 – General Information

ATTENTION

Before performing any service operation or other procedure described in this Section, refer to 00 Warnings,

Cautions and Notes for correct workshop practices with regard to safety and / or property damage.

1 General Information ...............................................................................................................................3

1.1 Introduction............................................................................................................................................................ 3

1.2 Emission Control................................................................................................................................................... 4

Euro 2 Emissions Standards ................................................................................................................................ 4

Euro 3 Emissions Standards ................................................................................................................................ 4

2 Component Locations ...........................................................................................................................5

2.1 Cylinder Numbering............................................................................................................................................... 5

2.2 Engine Compartment............................................................................................................................................. 6

2.3 Engine..................................................................................................................................................................... 7

Alloytec................................................................................................................................................................... 7

Alloytec 190 / High Output .................................................................................................................................... 8

All Engines ............................................................................................................................................................. 9

2.4 Manual Transmission .......................................................................................................................................... 10

2.5 Interior .................................................................................................................................................................. 11

3 System Operation.................................................................................................................................12

3.1 Fuel Delivery System........................................................................................................................................... 12

Fuel System Pressure ......................................................................................................................................... 12

Fuel Injection System.......................................................................................................................................... 13

Short Term Fuel Trim....................................................................................................................................... 13

Long Term Fuel Trim........................................................................................................................................ 13

3.2 Air / Fuel Control System.................................................................................................................................... 14

Starting Mode....................................................................................................................................................... 14

Run Mode ............................................................................................................................................................. 14

Open Loop Mode.............................................................................................................................................. 14

Closed Loop Mode........................................................................................................................................... 14

Acceleration Mode............................................................................................................................................... 14

Deceleration Mode............................................................................................................................................... 14

Fuel Shut-off Mode ............................................................................................................. ................................. 15

Battery Voltage Correction Mode....................................................................................................................... 15

Limp Mode............................................................................................................................................................ 15

Engine Protection Mode...................................................................................................................................... 15

Clear Flood Mode................................................................................................................................................. 15

3.3 Ignition Control System ...................................................................................................................................... 16

3.4 Starter Motor Operation ...................................................................................................................................... 17

Auto Start Feature................................................................................................................................................ 17

Clutch Pedal Position Switch.............................................................................................................................. 17

3.5 Throttle Actuator Control System ...................................................................................................................... 18

Description........................................................................................................................................................... 18

Throttle Body Relearn Procedure....................................................................................................................... 19

TAC System Default Actions / Reduce Power Modes....................................................................................... 19

Forced Engine Shutdown.................................................................................................................................... 19

3.6 Camshaft Position Actuator Control System .................................................................................................... 20

Operation.............................................................................................................................................................. 21

Variable Valve Timing Phases ......................................................................................................................... 21

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3.7 Cruise Control System ........................................................................................................................................ 23

3.8 Brake Torque Management................................................................................................................................. 24

3.9 Emission Control Systems.................................................................................................................................. 25

Evaporative Emission Control System .............................................................................................................. 25

Engine Ventilation System.................................................................................................................................. 26

3.10 Serial Data Communication System................................................................................................................... 27

3.11 Self Diagnostics System ..................................................................................................................................... 30

3.12 Service Programming System............................................................................................................................ 31

3.13 Theft Deterrent System ....................................................................................................................................... 32

4 Component Description and Operation.............................................................................................33

4.1 A/C Refrigerant Pressure Sensor....................................................................................................................... 33

4.2 Brake Pedal Switches.......................................................................................................................................... 34

Stop Lamp and BTSI Switch Assembly ............................................................................................................. 34

Cruise Control Release and Extended Brake Travel Switch Assembly.......................................................... 34

4.3 Barometric Pressure Sensor............................................................................................................................... 35

4.4 Camshaft Position Sensor .................................................................................................................................. 36

4.5 Crankshaft Position Sensor................................................................................................................................ 37

4.6 Engine Control Module........................................................................................................................................ 38

4.7 Engine Coolant Temperature Sensor................................................................................................................. 39

4.8 Electric Cooling Fans.......................................................................................................................................... 40

4.9 Engine Oil Level and Temperature Sensor........................................................................................................ 41

Engine Oil Temperature Sensor ......................................................................................................................... 41

Engine Oil Level Sensor...................................................................................................................................... 42

4.10 Engine Oil Pressure Sensor................................................................................................................................ 43

4.11 Fuel Injectors........................................................................................................................................................ 44

4.12 Fuel Rail Assembly.............................................................................................................................................. 45

4.13 Heated Oxygen Sensors...................................................................................................................................... 46

LSF 4.2 Two-step Planar Heated Oxygen Sensors ........................................................................................... 46

LSU 4.2 Wide-band Planar Heated Oxygen Sensors ........................................................................................ 48

4.14 Ignition Coil and Spark Plug............................................................................................................................... 50

4.15 Intake Air Temperature Sensor........................................................................................................................... 51

4.16 Intake Manifold Runner Control Valve ............................................................................................................... 52

4.17 Knock Sensor....................................................................................................................................................... 53

4.18 Mass Air Flow Sensor.......................................................................................................................................... 54

Air Intake System................................................................................................................................................. 54

Mass Air Flow Sensor.......................................................................................................................................... 54

Construction..................................................................................................................................................... 55

Operation ......................................................................................................................................................... 55

4.19 Vehicle Speed Sensor – Manual Transmission Only........................................................................................ 56

5 Abbreviations and Glossary of Terms...............................................................................................57

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1 General Information

The V6 engine management system

incorporates functions and components that

could cause personal injury or vehicle

damage. Refer to Section 6C1-2 Engine

Management – V6 – Diagnostics, and

Section 6C1-3 Engine Management – V6 –

Service Operations, before attempting any

diagnosis or repairs.

1.1 Introduction

For MY2006 vehicles, in addi tion to the engine design features utilised i n the MY2005 engine management system and

to comply with the Euro 3 emission regulations, further enh ancements have been made to increase the combustion

efficiency and improve the exhaust emission results.

Essentially, these items are:

• Dual spray fuel injectors are now used. The use of this spray pattern is used in engines with two intake valves per

cylinder. The dual spr ay is achieved by having two openings in the spray orifice disc that are arranged in such a

way that two fuel sprays result, being aimed at each intake valve port.

• Close coupled catalytic converters are retained with improved efficiencies through the use of revised amounts and

relative concentration levels of precious metals in each of the two catalytic converters.

• Pre and post catalytic converter heated oxygen sensors are now fitted to all V6 variants. The two designs are LSU

4.2 (pre-catalytic converter) and LSF 4.2 (post-catalytic converter. Both are of Bosch des ign.

• Both the engine and automatic transmission calibrations have been revised. As an example, the use of misfire

detection is now utilised and this feature involves the addition of a number of new diagnostic trouble codes (DT Cs).

Also, the 4L60-E and 4L65-E automatic transmissions are fitted with an input speed sensor.

• To ensure maximum oxygen sensor efficiencies, additional DT Cs are also directed to these highly sensitive

sensors.

• The additional diagnostic trouble codes (DTCs) are:

− Pre Catalytic Converter O2 Sensor Circuit Slow Response – P0133, P0153.

− Post Catalytic Converter O2 Sensor Circuit Slow Response – P0139, P0159.

− Misfire – P0300, P0301, P0302, P0303, P0304, P0305, P0306.

− Invalid Signal from TCM (Transmission Control Module) – P0864.

− Brake Switch Circuit – P0571.

− Post Catalyst O2 Sensor Fuel Trim Above / Below Upper / Lower Limits – P2096, P2097, P2098, P2099.

− Fuel Trim – P2177, P2178, P2179, P2180, P2187, P2188, P2189, P2189, P2190.

− Pre Catalytic Converter O2 Sensor – System Too Lean / Too Rich – P2195, P2196, P2197, P2198.

− Pre Catalytic Converter O2 Sensor Pump Current Trim Circuit – P2626, P2627, P2628, P2629, P2630,

P2631.

Refer to 6 Diagnostic Trouble Code tables, in Section 6C1-2 – Engine Management – V6 – Diagnostics for details.

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1.2 Emission Control

Euro 2 Emissions Standards

MY2005 vehicles were configured to comply with Euro 2 vehicle emissions standards. Euro 2 is a Europe an standard

which sets vehicle emissions targets to compel vehicle manufacturers to reduce harmful vehicle emissions such as

carbon monoxide (CO), Hydrocarbons (HC) and the various oxides of nitrogen (NOx).

Australian Design Rule 79/00 implements the 'Euro 2' exhaust and evaporative emissions requirements for light vehicles

to reduce air pollution. The following tests are prescribed:

• average tailpipe emissions after a cold start,

• carbon monoxide emission at idling speed,

• emission of crankcase gases,

• evaporative emissions, and

• durability of pollution-control d evices.

Euro 3 Emissions Standards

MY2006 vehicles have been configured to comply with Australian Design Rule (ADR) 79/01 which adopts the technical

requirements of the European Council Directive 98/69/EC. Commonly referred to as ‘Eur o 3’, the new legislation modifies

the exhaust emissions, compared to the pr evious ADR 79/00 (or ‘Euro 2’) vehicle emissions standards.

ADR 79/01 implements the 'Euro 3' exhaust and ev aporative emissions requirements for petrol fuelle d passenger cars,

forward control vehicles and passenger off-road vehicles with a Gross Vehicle Mass (GVM) up to 3.5 tonnes. All new

vehicles within these categories and first registered from January 1, 2006 must comply with ADR 79/01.

The next table sho ws a comparison between the existing ADR 37/01 (‘Euro 2’) an d ADR 79/01 (‘Euro 3’)

Hydrocarbons

Carbon

Monoxide (g/km) Exhaust

(g/km) Evaporative

(g/test)

Oxides of Nitrogen

(g/km) Particulate

Matter (g/test)

ADR 37/01 (Petrol) 2.2 — 2 — —

ADR 79/01 (Petrol,

LPG, CNG) 2.3 0.2 2 0.15 0.05

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2 Component Locations

2.1 Cylinder Numbering

Engine cylinder identification follows the inter national

standard OBD II. This standard calls for the engine cylinder

bank number one to be identified by the location of cylinder

number one. Therefore the numbering for the V6 engine is:

The V6 engine cylinders are numbered as follows:

• 1, 3, 5 – Right-hand side (Bank 1),

• 2, 4, 6 – Left-hand side (Bank 2).

The engine firing order is 1, 2, 3, 4, 5, 6.

Figure 6C1-1 – 1

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2.2 Engine Compartment

Figure 6C1-1 – 2

Legend

1 Mass Air Flow (MAF) Sensor 2 Air-conditioner Refrigerant Pressure Sensor

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2.3 Engine

Alloytec

Figure 6C1-1 – 3

1 Barometric Pressure (BARO) Sensor

2 Ignition Coil Assembly6 (six places)

3 Spark Plug (six places)

4 Throttle Body Assembly

5 Heated Oxygen Sensor (HO2S), Pre-Catalyst (two places)

6 Crankshaft Position (CKP) Sensor

7 Engine Control Module (ECM)

8 Heated Oxygen Sensor (HO2S), Post-Catalyst (two places)

(MY2006 Euro 3)

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Alloytec 190 / High Output

Figure 6C1-1 – 4

Legend

1 Barometric Pressure (BARO) Sensor

2 Intake Manifold Runner Control (IMRC) Valve

3 Ignition Coil Assembly (six places)

4 Spark Plug (six places)

5 Throttle Body Assembly

6 Engine Control Module (ECM)

7 Crankshaft Position (CKP) Sensor

8 Heated Oxygen Sensor (HO2S), Pre-Catalyst (two places)

9 Heated Oxygen Sensor (HO2S), Post-Catalyst (two places)

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All Engines

Figure 6C1-1 – 5

Legend

1 Camshaft Position (CMP) Actuator Solenoid, Alloytec

(two places), Alloytec190 / High Output (four places)

2 Camshaft Position (CMP) Sensor, Alloytec (two places),

Alloytec190 / High Output (four places)

3 Fuel Rail Assembly

4 Fuel Injector (six places)

5 Evaporative Canister Purge (EVAP) Valve

6 Engine Coolant Temperature (ECT) Sensor

7 Knock (KS) Sensor (two places)

8 Engine Oil Pressure Sensor

9 Engine Oil Level / Temperature Sensor

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2.4 Manual Transmission

Figure 6C1-1– 6

Legend

1 Vehicle Speed Sensor (VSS)

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2.5 Interior

Figure 6C1-1 – 7

Legend

1 Check Powertrain Icon (MY2005 Euro 2)

2 Malfunction Indicator Lamp (MIL) (MY2006 Euro 3)

3 Data Link Connector (DLC)

4 Clutch Pedal Cruise Control Cancel Switch

5 Clutch Pedal Position Switch

6 Extended Brake Pedal Travel and Brake Pedal Cruise

Control Cancel Switch

7 Stop Lamp and BTSI Switch Assembly

8 Accelerator Pedal Assembly

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3 System Operation

The engine control module (E CM) is the control centre of the V6 engine management system. The ECM constantl y

monitors and evaluates inputs from various sensors and switches. Based on these inputs, the ECM controls the

operation of the engine management system. Refer to Figure 6C1-1 – 8 for the illustration of the inputs and outputs of

the ECM.

Figure 6C1-1 – 8

3.1 Fuel Delivery System

Fuel System Pressure

When the ignition s witch is turned on, the ECM energises the fuel pump circuit and the fuel pump runs and builds up

pressure in the fuel system. The fuel pump will continue to operate if the engine is started or as long as the engine is

cranking or running and the ECM detects crankshaft position (CKP) sensor signal pulses. If the CKP sensor signal

pulses stop, the ECM de-energises the fuel p ump circuit within two seconds, which stops the fuel pump operation.

The vehicle is fitted with a modular fuel pump and sender assembly that provides delivery of fuel from the fuel tank and

information on the fuel level. The fuel del ivery system is a single line, on-demand design. With the fuel pressure regulator

incorporated into the modular fuel pump and sender assembly, the need for a return pipe from the engine is eliminated.

The electric fuel pump contained in the modular fuel pump and sender assembly provides fuel at a pressure greater than

the regulated pressure which is supplied to the fuel rail. The fuel is then distributed through the fuel rail to six injectors

located directly above each cylind er’s two intake valves.

Having a single line fuel suppl y system reduces the internal temperature of the fuel tank by not returning hot fuel from the

engine. In reducing the internal temperature of the fuel tank, lower evaporative emissions are achieved.

Unleaded fuel must be used to ensur e correct emission parameters and engine operation. Leaded fuel damages the

emission control system and use of leaded fuel can result in loss of emission warranty. Using unle aded fuel will also

minimise any spark plug fouling and extend engine oil life.

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Fuel Injection System

Each cylinder of the V6 engine is fitted with one fuel injector. The engine control relay applies ignition positive voltage to

the fuel injector ignition circuit. The ECM controls the operation of the fuel injectors by applying a pulse width modulated

(PWM) ground to the fuel injector control circuit to control each fuel injector on-time.

While the engine is running, the ECM constantly monitors the various inputs and recalculates the appropriate on-time for

each injector. The calculatio n is based on the following:

• the injector flow rate,

• mass of fuel passed by the energised injector per unit of time,

• the desired air / fuel ratio, and

• actual air mass in each cylinder.

The ECM calculates the duration of the fuel injector on-time to deliver the correct amount of fuel for optimum drivability

and emission control. The period of time the fuel i njector is e nergised is called the injector on-time and is measured in

milliseconds (thousandths of a second).

The V6 engine uses the sequential fue l injection system. Each fuel injector is energised individua lly at the correct

moment during its firing stroke as the cylinder’s intake valves are closing to provide enough time for the fuel to atomise

completely and mix with the intake air.

Short Term Fuel Trim

The short term fuel trim (STFT) represents the duration of the fuel injector on-time as calculated by the ECM while the

ECM is in closed loop mode. The STFT allows the ECM to calculate the fuel injector on-time based on the heated

oxygen sensor (HO2S) signal input to the ECM. Therefore, the STFT is disabled when the ECM is in Open Loo p mode.

• If the air / fuel mixture in the exhaust is balanced (l ambda = 1) or when the STFT is disabled, the STFT value

is 0%.

• When the HO2S sends an input signal to the ECM indicating the air / fuel mixture is rich, the STFT will be less

than 0%, which indicates the ECM is decreasing the fuel injector on-time to reduce the amount of fuel i n the air /

fuel mixture.

• When the HO2S sends an input signal to the ECM indicating the air / fuel mixture is lean, the STFT will be greater

than 0%, which indicates the ECM is increasing the fuel injector on-time to increase the amount of fuel in the air /

fuel mixture.

The percentage values of the STFT range from -25% – 25% and are directly proportional to the duration of the fuel

injector on-time.

Long Term Fuel Trim

The ECM stores the long term fuel trim (LTFT) in its memory to adjust the fuel injector on-time according to the long term

changes or deterioration in the engin e components. The normal LTFT value is 0%.

The following describes the LTFT operation when the engine air filter is dirty that causes a restricted intake airflow fault

condition:

1 The HO2S sends an input signal to the ECM the air / fuel mixture is rich because of the reduced airflow. The ST FT

may reduce to a value of -10%, which decreases the fuel injector on-time to reduce the amount of fuel in the air /

fuel mixture supplied to the engi ne.

Without the use of the LTFT, the restricted airflow caused by the dirty air filter may reduce the STFT value to -10%

until the air filter is replaced. This will decrease the range of negative adjustment available to the STFT to

compensate for other factors.

2 When the ECM detects the STFT has remained at -10% for a specific period, the ECM switches to the LTFT. The

LTFT adjusts the duratio n of the fuel i nj ector on-time u ntil th e air / fuel mixture in the e xhaust is balanced

(lambda = 1) and the STFT valu e returns to 0%.

3 The ECM stores this Long Term FT value in its memory, which is used to calculate the base fuel injector on-time.

The percentage values of the Long Term FT range from -100% – 100%. If the ECM detects the LTFT values are outside

the specified percentage range for a predetermined period, the ECM will set a diag nostic trouble code and switch to open

loop mode.

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3.2 Air / Fuel Control System

The engine control module (E CM) controls the amount of air and fuel delivered into each of the engine cylinders. Based

on the various ECM inputs, the ECM switches to the following air / fuel control system mode to provide the optimum

air / fuel ratio under all engine operating conditions.

Starting Mode

When the ignition switch is moved to the START position and the engine begins to turn, a prime pulse may be injected to

speed starting. As soon as the ECM receive s an input signal from the camshaft position (CMP) and crankshaft position

(CKP) sensor and determines which cylind er is in the firing stroke, the ECM applies a pulse width modulated (PWM)

ground to the injector control circuit. The ECM monitors mass air flow, intake air temperature, engine coolant

temperature, and throttle position to determine the req uired fuel injector on-time required for starting the engine.

Run Mode

The engine switches to run mode when the engine speed reaches 480 r.p.m. after being started. The run mode has two

sub-modes called Open Loo p and Closed Loop.

Open Loop Mode

The heated oxygen se nsor (HO2S) does not produce a usable signal voltage output until it reaches operating

temperature. Therefore, while the HO2S is below its operating temperature, the ECM switches to open loop mode.

In open loop, the ECM ignores the signals from the HO2S and calculates the required injector pulse width based

primarily on inputs from the mass air flow (MAF), intake air temperature (IAT), and engine coolant temperature sensors.

The system will stay in the open loop mode until the HO2S produce a usable output.

Closed Loop Mode

Once the HO2S reaches operating temperature and starts producing its own signal voltage output, the ECM switches to

the closed loop mode.

In closed loop mode, the ECM initially calculates in jector pulse width based on the same sensors used in open loop, and

additionally the ECM uses the oxygen sensor signals to modify and fine tune the fuel pulse width calculations to precisely

maintain the ideal 14.7 to 1 air / fuel ratio.

Acceleration Mode

The ECM monitors and calculates inp ut sign als from the accelerator pedal position (APP) and MAF sensor signals to

determine when the vehicle is being accelerated. If the ECM detects the accelerator pedal is depressed and there is a

demand for the vehicle to accelerate, the ECM switches to acceleration mode. In acceleration mode, the ECM increases

the fuel injector on-time to provide more fuel accordingly.

Deceleration Mode

The ECM monitors and calculates inp ut sign als from the APP and MAF sensor signals to determine when the vehicle is

being decelerated. If the ECM detects the vehicle is decelerating, the ECM switches to deceleration mod e. In

deceleration mode, the ECM decreases the fuel injector on-time, or disables the fuel injectors for short periods, to reduce

exhaust emissions and improve fuel economy.

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Fuel Shut-off Mode

To protect the engine from damage or to improve the veh icle's driveability, the ECM switches to the fuel shut-off mode. In

fuel shut-off mode, the ECM performs the following:

• The ECM disables the six fuel injectors under the following conditions:

• ignition off – to prevent engine dieselin g,

• ignition on but no ignition refe rence signal – prevents flooding or backfir ing,

• at high engine speed – greate r than the red line (rev limiter),

• at high vehicle speed – gre ate r than the rated tire speed (vehicle speed limiter), or

• extended high speed closed throttle coast-down – reduc es engine emissions and increases engine braking.

• The ECM selectively disables the appropriate number of fuel injectors under the following conditions:

• torque management enabled – transmission shifts or abusive mane uvers, or

• traction control enabled – in c onjunction with brake application.

Battery Voltage Correction Mode

The ECM monitors the battery voltage circuit to ensure the voltage ava ilable to the engine management system stays

within the specified range. A low system voltage changes the voltage across the fuel injectors, which affects the fuel

injector flow rate. In addition, a lo w system voltage fault condition ma y cause other engine management system

components to malfunction.

The ECM switches to battery voltage correction mode when the ECM detects a low battery voltage fault condition. While

in battery voltage correction mode, the ECM performs the following functions to compensate for the low system voltage:

• increases the injector on-time to maintain the correct amount of fuel being delivered, and

• increases the idle speed to increase the gen erator outp ut.

Limp Mode

The programming in the ECM software allows the engine to run in a back-up fuel strategy or limp mode when the ECM

fails to receive signal inputs from critical sens ors or when a critical engine management fault condition exists.

The ECM switches to limp mode to enable the vehic le to be driven until service operations can be performed.

Engine Protection Mode

Engine protection mode is en gaged to protect engine components from friction damage in the eve nt of an engine over-

temperature condition being detected by the ECM.

When the ECM is in engine pr otection mode, fuel injectors are systematically disabled and re-activated. The injectors

that have been shut down allow the air being drawn into the engine to assist with engine cooling.

Clear Flood Mode

If the engine is flooded with fuel during starti ng and will not start, the clear flood mode can be manually selected b y

depressing the accelerator pedal to wide open throttle (WOT). In this mode, the ECM will completely disabl e the fuel

injectors, and will maintain this state during engine cranking as long as the ECM detects a WOT condition with engine

speed less than 1,000 rpm.

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3.3 Ignition Control System

The electronic ignition s ystem provides a sp ark to ignite the compressed air / fuel mixture at the correct time. The ECM

maintains correct spark timing and d well for all e ngine operating conditions. The ECM calculates the optimum spark

parameters from information received from the various se nsors and triggers the appropriate ignition modul e / coil to fire

the spark plug.

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3.4 Starter Motor Operation

The engine control module (E CM) controls the activation of the start relay in response to inputs from:

• Ignition switch,

• battery,

• theft deterrent engine crank inhibitor (a function of the theft deterrent system), and

• automatic transmission gear selector position / clutch pedal position switch for vehicles with manual transmissions.

Auto Start Feature

Once the ignition switch has been turned to the START position, the starter motor will crank the engine.

If the ignition switch is returned to the ON position before the engine has started, the starter motor will continue to

operate until the engine starts. If the engine fails to start, cranking will continue for approximately four sec onds from

when the ignition switch was returned to the ON position.

Turning the ignition switch to the OFF position will cancel the Auto Start and the starter motor will stop cranking. For

further information on the starter motor system, refer to Section 6D1-2 Starting System – V6.

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3.5 Throttle Actuator Control System

Description

The throttle actuator control (TAC) system is used to impr ov e emissions, fuel economy and driveabi lity. The TAC system

eliminates the mechanical link between the accelerator pedal and the throttle plate and eliminates the need for a cruise

control module and idle air co ntrol motor. The TAC system comprises of:

• The accelerator pedal assem bly which includes:

• the accelerator pedal,

• the accelerator pedal position (APP) sensor one,

• the accelerator pedal position (APP) sensor two.

Figure 6C1-1 – 9

To avoid serious personal injury, never

attempt to rotate the throttle plate manually

whilst the throttle body harness connector is

connected to the throttle bod y.

• The throttle body assembly which i nclu des:

• the throttle position (TP) sensor one,

• the throttle position (TP) sensor t wo,

• the throttle actuator control (TAC) motor, and

• the throttle plate.

• The engine control module (E CM).

Figure 6C1-1 – 10

The ECM monitors the accelerator pedal position through the two APP sensors and processes this information along with

other system sensor inputs to command the throttle plate to a certain position.

The throttle plate is controlled by a direct current motor called the throttle actuator control motor. The ECM operates this

motor in the forward or reverse direction by controlling battery voltage and / or ground to two internal drivers. The throttle

plate is held at a rest position of seven percent open using a constant force return spring. This spring holds the throttle

plate to the rest position when there is no current flowing to the actuator motor.

The ECM monitors the throttle plate angle through two TP sensors. Using this information, the ECM can precisely adjust

the throttle plate.

The ECM performs diagnostics that monitor the voltage levels of both APP sensors, both TP sensors and the throttle

actuator control motor circuit. It also monitors the spring return rate. T hese diagnostics are performed at different times

based on whether the engine is running, not running, or whether the ECM is currently in a throttle body relearn

procedure.

Two sensors within the accelerator ped al assembly and throttle body assembly are used to provide redundancy. If a

malfunction is detected, the throttle plate is moved to a pre-determined position.

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Every ignition cycle, the ECM performs a quick throttle return spring test to ensure the thr ottle plate can return to the

seven percent rest position from the zero percent position. T his is to ensure the throttle plate can be bro ught to the rest

position in case of an actuator motor circuit failure.

Throttle Body Relearn Procedure

The ECM stores values that include the lowest possible TP sensor positions (zero percent), the rest positions (seven

percent), and the spring return rate. T hese values will only be erased or overwritten if the ECM is reprogrammed or if a

throttle body relear n procedure is performed.

NOTE

If the battery has been disconnected, the ECM

performs a throttle body relearn procedure once

the battery has been reconn ected and the ig nition

turned on.

The ECM performs a throttle body relearn procedure anytime the ignition is turned on and the following conditions have

been met:

• the engine has been off for greater than 29 seconds,

• the engine speed is less than 40 rpm,

• the vehicle speed is 0 km/h,

• the engine coolant temperature (ECT) is 5 – 60°C; if Tech 2 is used to perform the relearn procedure, the ECT is

5 – 100°C,

• the intake air temperature (IAT) is greater than 5 – 60°C; if Tech 2 is used to perform the relearn procedure, the

IAT is 5 – 100°C,

• the APP sensor angle is less than 15 percent, and

• ignition voltage is greater than 10 V.

The throttle body relearn procedur e is performed 29 seconds after the ignition is turned on. The ECM commands the

throttle plate from the rest position (even percent open) to full closed (zero percent), then to around 10 percent open.

This procedure takes about six – eight sec on ds. If any faults occur in the TAC system, a DTC sets. At the start of this

procedure, the Tech 2 TAC Learn Counter parameter should display 0, then count up to 11 after the procedure is

completed. If the counter did not start at 0, or if the counter did not end at 11, a fault has occurred and a DTC should set.

TAC System Default Actions / Reduce Power Modes

The ECM switches to the following reduce power modes if the ECM detects a fault condition in the TAC system:

• If an APP sensor circuit fault or TP sensor circuit fault is detected, the ECM limits engine torque so the vehicl e

cannot reach speeds of great er than 100 km/h. The ECM remains in this reduce power mode during the entire

ignition cycle, even if the fault is corrected.

• If there is a fault condition with the throttle actuator control circuits, a throttle actuator command vs. actual position

fault, a return spring check fault, or a TP sensor one circuit fault, the ECM limits engine speed to 2500 r.p.m. and

three – six fuel injectors are ra ndomly disabled. At this time the reduce power indicator is commanded on. The

ECM remains in the reduce power mode during the entire ignition cycle even if the fault is corrected.

NOTE

If a TP sensor one or throttle actuator control

circuit fault is present at the time the vehicle is at

idle, with no accelerator pedal angle, the engine

may stall.

Forced Engine Shutdown

A further safety feature which is built into the TAC system is that the ECM will initiate an engine shut down if, the ECM

internal monitoring functions detects a serious internal fault, the fuel injectors will be turned off.

Engine Management – V6 – General Information Page 6C1-1–20

Page 6C1-1–20

3.6 Camshaft Position Actuator Control

System

The Alloytec engine has variable timi ng on the intake camshafts only, while the Alloytec1 90 / High Output engine has

variable timing on both intake and exhaust camshafts.

NOTE

The parameters under which variable valve

timing will occur is very complex. The conditions

outlined below is a brief summary of the

conditions the ECM uses to determine the point

at which variable valve timing will commence:

The ECM will only initiate variable timing if all of the following conditions exist:

• Engine coolant temperature is greater tha n -12°C a nd less than 130°C,

• air intake temperature is great er than -48°C,

• engine oil temperature is greater than -10°C and less than 155°C, and

• engine speed is greater than 1000 rpm for longer than two seconds, and less than 7320 rpm.

The ECM adjusts the timing of each camshaft by applying a pulse width modulated (PWM) control signal to the camshaft

position (CMP) actuator solenoid valve (1), which in turn controls the oil pressure / flow to the CMP actuator (2).

Refer to Figure 6C1-1 – 11.

The engine control module (E CM) advances or retards the camshaft timing, based on various system inputs, to provide

optimum valve overlap over the entire operating range of the engine.

The intake camshafts can be advanced u p to 25 camsh aft degrees, and the exhaust camshafts can be retarded up to 25

camshaft degrees.

The crankshaft position (CKP) sensor an d the camshaft position (CMP) sensors are used to monitor changes in the

camshaft positions.

Figure 6C1-1 – 11

Engine Management – V6 – General Information Page 6C1-1–21

Page 6C1-1–21

Operation

A CMP actuator assembly is fitted to each variable camshaft (1). The actuator has an outer housing (2) that is driven by

the engine timing chain, and an inner housing (3), refer to Figure 6C1-1 – 12.

When the engine is not running or at idle, a lock pin (4) contained in each actuator locks the camshaft to the outer

housing, to prevent camshaft timing adjustme nt.

Figure 6C1-1 – 12

Variable Valve Timing Phases

Variable Valve Timing – Increase

When the ECM commands the actuator sole noid valve (1) to redirect the oil pressure supply to the CMP actuator (2),

the oil pressure supply (A) moves the lock pin (3) in the direction of the arrow (B) to unlock the actuator, refer to

Figure 6C1-1 – 13.

At the same time, oil pressure (A) is applied to the one side of each of the four fixed vanes (4). The oil pressure builds

up, until it overcomes the CMP actuator return spring (not shown) and starts to advance the camshaft (intake) or retard

the camshaft (exhaust). As the camshaft starts to move, the oil (C) on the opposite side of the vane where the oil

pressure is currently being applied, drains back through the CMP actuator oil gall eries and out through the actuator

solenoid valve (D).

Figure 6C1-1 – 13

Engine Management – V6 – General Information Page 6C1-1–22

Page 6C1-1–22

Variable Valve Timing – Maintained

When the valve timing has been adv anced or retarded, and the timing is to be mainta ined, the actuator solenoid valve (1)

applies oil pressure (A) and (C) to both sides of the fixed vane.

Figure 6C1-1 – 14

Variable Valve Timing – Reduced

When the amount of variable valve timing is reduced, the actuator solenoid valve (1) applies oil pressure (C), to one side

of the vane (2) (this is to the opposite side of the vane used to increase the valve timing).

As the camshaft begins to move, the oil (A) on the opposite side of the vane where the oil pressure is currently being

applied, drains back through the CMP actuator oil galleries and out throug h the act uator solenoid valve (D).

Figure 6C1-1 – 15

Engine Management – V6 – General Information Page 6C1-1–23

Page 6C1-1–23

3.7 Cruise Control System

The cruise control s ystem inte grates with the engine control module (ECM) through the powertrain interface module

(PIM), to control the electronic throttle actuator and maintain the vehicle at the speed set by the driver.

When the cruise ON-OFF button is pressed, the PIM, on receiving the input from the cruise control s witch, outputs a

signal via the serial data bus to the ECM. The ECM recognises the command from the PIM to engage the cruise control.

The ECM then provides a signal for the instru ment cluster, via the PIM, to inform the user that cruise control is engaged.

The user activates the cruise control at a de sired speed greater than 40 km/h by rotating the cruise control switch

assembly to SET–DECEL. The PIM, on receiving the input from the cruise control switch, outputs a signal via the serial

data bus to the ECM. The ECM then activates the cruise control and sets the speed. The ECM receives all the various

inputs required to maintain the correct speed and th en controls the throttle plate depending on the load on the engine

(ascending or descending hill s, etc).

The cruise control is deactivated b y either pressing the brake pedal, clutch pedal or by the cruise control ON-OFF button.

In each of these instances, the ECM receive s an input when any of these switches are activated. For further information

on the cruise control system, refer to Section 12E Cruise Control.

Engine Management – V6 – General Information Page 6C1-1–24

Page 6C1-1–24

3.8 Brake Torque Management

Brake torque management places limits on engine torque when the brakes are applied, regardless of the accelerator

pedal position (APP). The conditions under which brake torque management occur are as follows:

• The accelerator has been depressed before the brakes are applied,

• the brakes are applie d and the ECM receives an input from the stop lamp s witch,

• vehicle speed is greater than 5 km/h,

• engine speed is greater than 1200 rpm and

• conditions exist for greater than 2.5 seconds.

When brake torque management has been implemented, the torque is reduced by altering the throttle plate opening by

25%. The ECM will monitor the rate at which the vehicle is slowing and adjust the throttle plate opening accordingly.

Engine Management – V6 – General Information Page 6C1-1–25

Page 6C1-1–25

3.9 Emission Control Systems

Evaporative Emission Control System

The evaporative emission con t rol system used is the

activated carbon (charcoal) canister storage method. Fuel

vapour is drawn from the fuel tank into the canister where it

is held by the activated carbon until the ECM commands the

evaporative emission (EVAP) purge solenoid valve to open.

The ECM energises the EVAP purge sole noid valve by

applying a pulse width modulated (PWM) ground to the

EVAP purge solenoid valve control circuit.

Figure 6C1-1 – 16

When ECM commands the EVAP valve (1) to open, the fuel

vapours are drawn from the canister line (2) into the intake

manifold where it is consumed in the normal combusti on

process.

Figure 6C1-1 – 17

The ECM energises the EVAP valve when the appropriate conditions have been met, such as:

• engine coolant temperature is less than 20°C at cold start up and the engine has been running longer than

three minutes and 10 seconds, or

• engine coolant temperature is greater than 80°C and the engine has been runn ing longer than five seconds, or

• engine is not in decel fuel cut-off mode and the throttle opening is less than 96%, or

• the engine is in closed loop fuel mode.

A higher purge rate is used under co nditions that are likely to produce large amounts of vapour, when the following

conditions have been met:

• intake air temperature is greater than 50°C, or

• engine coolant temperature is greater than 100°C, or

• the engine has been runn ing for greater than 15 minutes.

The EVAP purge PWM duty cycle varies according to operating conditions determined by mass air flow, fuel trim and

intake air temperature. The EVAP canister purge valve is re-enabled when throttle position angle decreases below 96%.

For further information on the evaporative emission control system, refer to Section 8A1 Fuel System.

Engine Management – V6 – General Information Page 6C1-1–26

Page 6C1-1–26

Engine Ventilation System

The engine ventilation system contains a positive crankcase

ventilation (PCV) valve (1) located in the righ t-hand

camshaft cover. A hose is routed from the PCV valve to

each side of the intake manifold which provides an even

distribution of crankcase fumes, thereb y impr oving spark

plug reliability and a reduction in emissions.

A breather pipe is routed from the intake manifold to the left-

hand camshaft cover and provides fresh filter ed air from the

intake duct to the engine.

For further information of the engine ventilati on system,

refer to Section 6A1 Engine Mechanical – V6.

Figure 6C1-1 – 18

Engine Management – V6 – General Information Page 6C1-1–27

Page 6C1-1–27

3.10 Serial Data Communication System

The engine control module (E CM) communicates directly with the following control units using the General Motors local

area network (GM LAN) serial data communication protocol:

• Transmission Control Modu le (TCM) (if fitted)

• ABS / TCS / ESP Electronic Control Unit (ECU) (if fitted)

• Steering Angle Sensor (SAS) (if fitted)

• Powertrain Interface Module (PIM)

There are of two communication systems that operate within the V6 engine vehicle structure, which are:

• General Motors Local Area Network (GM LAN)

• Universal Asynchronous Receive and Transmit (UART )

The body control module (BCM) is the UART ‘Bus Master’ that periodically polls (or surveys) each of the following

devices (if fitted) on the serial data bus ev ery 300 milliseconds (including the BCM itself), requesting status data.

Exceptions are the PIM and the audio head unit (AHU), which are polled every 150 milliseconds:

• V6 Engine Control Module (ECM) and Transmission Control Module (TCM), via the PIM

• V6 ABS / TCS / ESP and the Steering Angle Sensor, via the PIM

• Instrument cluster (INS)

• Occupant Climate Control (OCC) Modu le

• Audio Head Unit (AHU)

• Supplemental Restraint System (SRS) Sensing Diagnostic Module (SDM)

• Body Control Module (BCM)

• Tech 2 diagnostic scan tool

While there are other modules and devices connected to the serial data bus, they only monitor the b us for app licable

data that affects their functionality. These devices are:

• Telematics Control Module

• Memory Seat

Refer to Section 12J Body Control Module for further information.

Engine Management – V6 – General Information Page 6C1-1–28

Page 6C1-1–28

Figure 6C1-1 – 19 – Serial Data Communications

As the GM LAN serial data communication protocol is not compatible with the UART serial data communication protocol,

a powertrain interface module (PIM) is integrated into the serial data communication system to perform the following

tasks:

• Translate the GM LAN serial data transmitted b y the ECM, TCM and ABS / TCS ECU into a UART serial data that

can be received and recognised by the BCM, instrument cluster and other vehicle control modules.

• Translate the UART serial data transmitted by the BCM and other vehicle control modules into GM LAN serial data

that can be received and recognised by the ECM, TCM and ABS / TCS ECU.

• Translate the cruise control switch signal i nto a GM LAN serial data that can be received and recognised by the

ECM.

Engine Management – V6 – General Information Page 6C1-1–29

Page 6C1-1–29

Refer to Section 6E1 Powertrain Interface Module – V6 for additional details on PIM principles of operation.

1 The powertrain interface module (PIM) is required as the hardware and serial commu nications interface for the V6

engine. The PIM acts as a transparent bi-directional translation device that allows data to flow between modules

with GM LAN protocol and modules with UART protocol (refer Figure 6C1-1–19).

2 With the communication necessary between the V6 engine and transmission modules, there are instances where

the engine control module (ECM) could set a diagnostic trouble code (DTC) that would also be detected by the

transmission control module (TCM). Therefore, to ensure that the most efficient and effective diagnostic process is

followed, a structured approach to the diagno stic process for electrical systems within the vehicle is most important,

refer to Section 0D Vehicle Diagnostics.

Engine Management – V6 – General Information Page 6C1-1–30

Page 6C1-1–30

3.11 Self Diagnostics System

The ECM constantly performs self-diagnostic tests on the engine management system. W hen the ECM detects a

malfunction, it also stores a diagnostic trouble code (DTC). A stored DTC will identify the problem area(s) and is

designed to assist the technician in rectifying the fault. In addition, DTCs are classified as either Current or History DTC.

For MY2005 vehicles (Euro 2), depending on the type of

DTC set, the ECM may command the instrument cluster

multi-function display (MFD) Check Powertrain icon (1) to

activate and warn the driver there is a fault in the engine

management system.

Figure 6C1-1 – 20

With introduction of Euro 3 for MY2006 vehicles, the

instrument cluster is equipped with an emissions monitoring

system malfunction indicator lamp (MIL), which replaces the

Check Powertrain icon. The lamp is located in the warning

lamps panel beneath the fuel gauge.

Refer to Section 12C Instrumentation for further information

on the operation of the Check Powertrain icon or the

Malfunction Indicator Lamp (MIL).

Figure 6C1-1 – 21

Engine Management – V6 – General Information Page 6C1-1–31

Page 6C1-1–31

3.12 Service Programming System

The ECM has an electronically erasable programmable read only memory (EEPROM) where the software and calibration

information required to operate the engine management system are stored.

The ECM features a service programming system (SPS) to flash program the EEPROM in the ECM with the latest ECM

software to provide optimum performance, driveability and emissions control or to program a new ECM.

Flash programming refers to the SPS used to transfer (or download) ECM data from a computer terminal to the vehicle’s

ECM. The system is designed so the vehicle verification procedures are required to eliminate EEPROM tampering that

could increase engine emission levels.

There are three main flash pr ogramming techniques:

1 Direct programming (pass through). This is where the vehicle’s data link connector (DLC) is connected directly to a

computer terminal. On screen directions are then followed for downloading.

2 Remote Programming. Reprogramming inform ation is downloaded from a computer terminal to Tech 2. Tech 2 is

then connected to the vehicle’s DLC. On screen directions are then followed for downloading.

3 Off-board Programming. The off-board programming method is used when a re-programmable ECM must be

programmed while it is removed from the vehicle. For example, an independent repair facility may find it necessary

to replace a faulty ECM. On flash programming eq uipped vehicles, the replacement ECM must be progr ammed

with data for the specific vehicle identification number (VIN) or the vehicle may not operate prop erly.

Engine Management – V6 – General Information Page 6C1-1–32

Page 6C1-1–32

3.13 Theft Deterrent System

The vehicle incorporates a the ft deterrent system. After the ignition switch is turned to the ON position, and the

powertrain interface module (PIM) has authenticated the body control module (BCM), the PIM sends an encrypted

security code to the engine control module (ECM). T he ECM compares the received security code with its own security

code, and if it is valid, the ECM enables the vehicl e to be started. For further information and diagnosis of the theft

deterrent system, refer to Section 12J Body Control Module.

For further information on the PIM, refer to Section 6E1 Powertrain Interface Module – V6.

Engine Management – V6 – General Information Page 6C1-1–33

Page 6C1-1–33

4 Component Description and

Operation

4.1 A/C Refrigerant Pressure Sensor

The engine control module (ECM) applies a positive 5 V

reference voltage and ground to the air-conditioner (A/C)

refrigerant pressure sensor (1). The A/C refrigerant pressure

sensor provides signal voltag e to the ECM that is

proportional to the A/C refrigerant pressure. The ECM

monitors the A/C refrigerant pressure sensor signal voltage

to determine the refrigerant pressure.

• The A/C refrigerant pressure sensor voltage increases

as the refrigerant pressure increases.

• When the ECM detects the refrigerant pressure

exceeds a predetermined value, the ECM activates

the cooling fans to reduce the refrigerant pre ssure.

• When the ECM detects the refrigerant pressure is too

high or too low, the ECM disables the A/C clutch to

protect the A/C compressor from damage.

Figure 6C1-1 – 22

Engine Management – V6 – General Information Page 6C1-1–34

Page 6C1-1–34

4.2 Brake Pedal Switches

Stop Lamp and BTSI Switch Assembly

The stop lamp and BTSI s witch assembly (1) is located o n

the brake pedal support.

The engine control module (E CM) uses the stop lamp switch

signal voltage to determine when the brake pedal is

depressed.

The ECM uses this input for brake torque manag ement, for

cross referencing the stop lamp switch against the cruise

control cancel switch for correct operation etc. For further

information on brake torque management, refer to

3.8 Brake Torque Management.

The stop lamp switch is a normally open switch with the

brake pedal at rest.

Figure 6C1-1 – 23

Cruise Control Release and Extended Brake Travel Switch Assembly

The cruise control release and extended brake travel s witch assemb ly (2) is located on the brake pedal support. Refer to

Figure 6C1-1 – 23.

The engine control module (E CM) uses the cruise control release switch signal voltage to determine when the brake

pedal is depressed. T he ECM uses this input to cancel cruise control operation, for cross referencing the cruise co ntrol

release switch against the stop lamp s witch for correct operation etc.

The ECM uses the extended brake travel switch signal voltage to determine when full brake pedal travel has been

achieved. The ECM uses this input to compensate for the air being used by the brake booster.

Both of these switches are normally closed when the brake ped al is in the rest position, opening when the pedal is

pressed. Activation of this switch removes the signal to the ECM.

For further information on the cruise control system, refer to 3.7 Cruise Control System, refer to

3.8 Brake Torque Management.

Engine Management – V6 – General Information Page 6C1-1–35

Page 6C1-1–35

4.3 Barometric Pressure Sensor

The barometric pressure (BARO) sensor me asures

barometric (atmospheric) pressure. T he ECM uses this

signal to make corrections to the operating parameters of

the system based on changes in air density, since the

oxygen content of atmospheric air varies proportionally to air

density (barometric / atmospheric pressure). Barometric

pressure is affected mainly by altitude and climate.

The BARO sensor provides a voltage signal to the ECM that

is a function of barometric pressure. It does this through a

series of deformation resistors, which change resistance

when a mechanical force is applied. This force is applied to

the resistors by a diaphragm on which the atmospheric

pressure acts.

The ECM supplies the BARO sensor with a 5 V reference

and a ground circuit. Figure 6C1-1 – 24

Engine Management – V6 – General Information Page 6C1-1–36

Page 6C1-1–36

4.4 Camshaft Position Sensor

Alloytec engines are fitted with two camshaft position (CMP)

sensors, one for each intake camshaft. Alloytec 190 / High

Output engines have four, one for every camshaft.

The CMP sensors are used by the ECM to determine the

position of the camshafts. In conjunction with the crankshaft

position sensor, the CMP enables the ECM to determine

engine rotational position.

Figure 6C1-1 – 25

The CMP sensor operates on the dua l-Hall sensing

principle. The sensor co ntains two hall elements (1) which

operate in conjunction with a two-track trigger wheel (2)

mounted on the camshaft.

As the tracks (3) on the trigger wheel pass the elements,

magnetic flux affects a voltage in the Hall elements. The

integrated circuit inside the sensor conditions the signal

generated by the Hall eleme nts to provide a rectangular

wave on / off signal to the ECM.

The ECM supplies the CMP sensors with a 5 V reference

and ground circuit.

Figure 6C1-1 – 26

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Page 6C1-1–37

4.5 Crankshaft Position Sensor

In conjunction with the camshaft position sensor, the

crankshaft position (CKP) sensor enables th e ECM to

determine engine rotational position. The CKP is also

used to determine engine sp eed (rpm).

Figure 6C1-1 – 27

The CKP sensor (1) operates on the variable reluctance

(pulse generator) sensi ng principle. It contains a magnet

and pickup coil and is used in conjunction with a 58 tooth

ferromagnetic reluctor wheel (2) attached to the

crankshaft (3).

As the crankshaft rotates, the reluctor wheel revolves past

the CKP, causing fluctuations in the magnetic field inside

the sensor. This action creates an AC voltage across the

pickup coil which is processed by the ECM. An increase in

engine speed will increase the output voltage and

frequency.

The reluctor wheel teeth are placed six degrees apart.

Having only 58 teeth leaves a 12 de gree open span, which

creates a signature pattern that enables the ECM to

determine the crankshaft position. The ECM determines

which two cylinders are approaching the top dead centre

based on the crankshaft position sensor signal. The CMP

sensor signals are used by the ECM to determine which

cylinder is on the firing stroke. Figure 6C1-1 – 28

Engine Management – V6 – General Information Page 6C1-1–38

Page 6C1-1–38

4.6 Engine Control Module

Located at the right front of the engine assembly, the engine

control module (ECM) monitors input sig na ls from the

various sensors and switches connected to the engine

management system. The ECM processes this information,

to control the following:

• fuel delivery and inj ection system,

• throttle actuation system,

• inlet manifold runner control valve (Alloytec190 / High

Output engine only),

• camshaft position actuators,

• ignition system,

• on-board diagnostics,

• the engine cooling fans, and

• the air-conditioner compressor clutch ( where fitted).

The ECM supplies 5 V to the various sensors through p ull-

up resistors to the internal regulated power supplies.

The ECM controls output circuits such as the injectors,

cooling fan relays, etc. by applying control signal to the

ground circuits of the components through transistors or a

device inside the ECM called a driver. The exception to this

is the fuel pump relay control circuit. The fuel pump relay is

the only ECM controlled circuit where the ECM controls the

12 V sent to the coil of the relay. The ground side of the fuel

pump relay coil is connected to engine ground.

The ECM communicates directly with the various control

units within the vehicle using the General Motors local area

network (GM LAN) serial data communication protocol.

Refer to 3.10 Serial Data Communication System.

Figure 6C1-1 – 29

Engine Management – V6 – General Information Page 6C1-1–39

Page 6C1-1–39

4.7 Engine Coolant Temperature Sensor

The engine coolant temperature (ECT) sensor is a

thermistor, which is a resistor that changes its resistance

value based on temperature.

Figure 6C1-1 – 30

The ECT is mounted in the engine coolant stream and is a

negative temperature coefficient (NTC) type. Low engine

coolant temperature produc es a high sensor resistance

while high engine coo lant temperature causes low sensor

resistance.

Legend

A Temperature

B Resistance

The ECM provides a 5 V reference signal to the ECT and

monitors the return signal which enables it to calculate the

engine temperature.

The ECM uses this signal to make corrections to the

operating parameters of the system based on changes in

engine coolant temperatur e.

Figure 6C1-1 – 31

Engine Management – V6 – General Information Page 6C1-1–40

Page 6C1-1–40

4.8 Electric Cooling Fans

The ECM controls the operation of two dual speed electric

engine cooling fans. T he ECM operates the fans at either

low or high speed based on in puts from engine coolant

temperature, vehicle speed and air-conditioner request.

For further information on cooling fan operati on refer to

Section 6B1 Engine Co oling – V6.

Figure 6C1-1 – 32

Engine Management – V6 – General Information Page 6C1-1–41

Page 6C1-1–41

4.9 Engine Oil Level and Temperature

Sensor

The engine oil level (EOL) and temperature sensor is a dual

purpose sensor and is fitted in the engine su mp. It combines

a switch to signal oil level and a thermistor typ e temperature

sensor to provide oil temperature signal to the ECM.

Figure 6C1-1 – 33

Engine Oil Temperature Sensor

The engine oil temperature sensor is a negative

temperature coefficient (NTC) type. At low engine oil

temperature, the sensor produces a hig h resistance, whilst

at high temperature the sensor produces a low resistance.

Legend

A Temperature

B Resistance

The ECM provides a 5 V reference signal to the engine oil

temperature sensor and monit ors the return signal which

enables it to calculate the engine oil temperature.

The ECM uses oil temperatur e as one of the inputs in

determining the point at which camshaft phasing will

commence. For further information on camshaft phasing,

refer to 3.6 Camshaft Position Actuator Control System. Figure 6C1-1 – 34

Engine Management – V6 – General Information Page 6C1-1–42

Page 6C1-1–42

Engine Oil Level Sensor

The engine oil level sensor is comprised of a magnetic reed

switch (1) contained within the sensor, a float (2) and a

magnetic pin (3). The magnetic reed switch is a normally

open switch, which closes when a magnet fi eld is present.

When the engine oil leve l is within specifications, the pin on

the inside of the float is pushed up against the reed switch

(view A). When the oil level drops an d the magnetic pin

moves away from the reed switch (view B), the switch

contacts opens.

The ECM provides a 5 V reference signal to the engine oil

temperature sensor and monit ors the return signal. The

ECM only monitors the oil level signal prior to engine start-

up, and once the engine is cranking, the ECM disregards

the oil level sensor signal.

Figure 6C1-1 – 35

Engine Management – V6 – General Information Page 6C1-1–43

Page 6C1-1–43

4.10 Engine Oil Pressure Sensor

The engine oil pressur e (EOP) sensor measures engine oil

pressure. When the EOP sensor signal is below a certain

value, the ECM activates the Check Oil warning message in

the instrument cluster multi-function display (MFD).

Figure 6C1-1 – 36

The EOP sensor provides a voltag e signal to the ECM that

is a function of engine oil pressure. It does this through a

series of deformation resistors (1), which change resistance

when a mechanical force is applied. This force is applied to

the resistors by a diaphragm on which the engine oil

pressure acts (2).

The sensor has an internal ev aluation circuit (3) and is

provided with a 5 V reference voltage, a ground and a signal

circuit.

Figure 6C1-1 – 37

Engine Management – V6 – General Information Page 6C1-1–44

Page 6C1-1–44

4.11 Fuel Injectors

A fuel injector is a solenoid device that is cont rolled by the

ECM. The six injectors deliver a precise amount of fuel into

the intake ports as required by the engine.

Figure 6C1-1 – 38

The fuel port (1) connects to the fuel rail. A strainer (2) is

provided in the port to protect the injector from fuel

contamination.

In the de-energised state (no voltage), the valve needle and

sealing ball assembly (3) are held against a cone-s haped

valve seat (4) by spring force (5) and fuel pressure.

When the injector is energise d by the ECM, the valve

needle, which has an integr al armature, is moved upward by

the injector solenoids magnetic field, un-seating the ball.

For MY2005 vehicles: An orifice plate (6), located at the

base of the injector has four small holes which provide very

fine atomisation of the fuel. The plate is insensitive to fuel

deposits ensuring reliab le fuel delivery.

For MY2006 vehicles: The orifice plate (6), l ocated at the

base of the injector has openings that are arr anged in such a

way that two fuel sprays, angled at 20° apart and at 90° to

the connector plug, emerge from the injector.

With both type of injectors, the fuel is directed at each of the

intake valves, causing the fuel to become further vaporised

before entering the combustion chamber.

Figure 6C1-1 – 39

Engine Management – V6 – General Information Page 6C1-1–45

Page 6C1-1–45

4.12 Fuel Rail Assembly

The fuel rail assembly is mou nted on th e lower intake

manifold and distributes the fuel to each c ylin der through

individual fuel injectors. The fuel rail assembly consists of:

• the pipe that carries fuel to each injector,

• a fuel pressure test port,

• six individual fuel inj ectors,

• wiring harness, and

• wiring harness tray.

Figure 6C1-1 – 40

Engine Management – V6 – General Information Page 6C1-1–46

Page 6C1-1–46

4.13 Heated Oxygen Sensors

The heated oxygen se nsors (HO2S) are mounted in the exhaust system and enable the ECM to measure oxygen

content in the exhaust stream. The ECM uses this information to accurately control the air / fuel ratio, because the

oxygen content in the exhaust gas is indicativ e of the air / fuel ratio of engine combustion.

When the sensor is cold, it produces little or no signal voltage, therefore the ECM only reads the HO2S signal when the

HO2S sensor is warm. As soon as the HO2S are warm and outputting a usable signal, the ECM begins making fuel

mixture adjustments base d o n the HO2S signals. This is known as closed loop mode.

MY2005 vehicles with Alloyte c engines are fitted with two LSF 4.2 two-step planar t ype H O 2S, one in each exhaust pipe

upstream of the catalytic converter. Alloytec190 / High Output engines have four HO2S, one LSU 4.2 wide-band planar

type HO2S upstream of the catalytic converter in each exhaust pipe, and one LSF 4.2 t wo-step planar type HO2S in

each exhaust pipe downstream of the catalytic converter.

With the introduction of Euro 3 vehicle emis sions on MY2006 vehicles, all variants of the Alloytec engine are fitted with

four HO2S, one LSU 4.2 wide-band planar type HO2S upstream of the catalytic converter in each exhaust pipe, and one

LSF 4.2 two-step planar type HO2S in each exhaust pipe downstream of the catalytic converter.

LSF 4.2 Two-step Planar Heated Oxygen Sensors

The LSF 4.2 two-step planar h eated oxygen sensors have

four wires:

• The internal heater element supply, which has 12 V

continually applied whenever the ignition is on.

• Heater element ground – T he ECM applies pulse

width modulated (PWM) ground to the HO2S heater

control circuit to control the rate at which the sensor

heats up. This reduces the risk of the sensor bein g

damaged from heating up too quickl y under certain

conditions such as extreme cold temperatures. Once

the sensor has reached the desired operating

temperature, the ECM will monitor and continue to

maintain the sensor temperature.

• Sensor signal to the ECM.

• Sensor ground.

Legend

1 Protective Tube

2 Ceramic Seal Packing

3 Sensor Housing

4 Ceramic Support Tube

5 Planar Measuring Element

6 Protective Sleeve

7 Connection Cable

Figure 6C1-1 – 41

Engine Management – V6 – General Information Page 6C1-1–47

Page 6C1-1–47

Measurement is achieved b y comparing the oxygen content

of the exhaust gas to the oxygen content of a reference gas

(outside air) using the Nernst principle. Oxygen molecules

from the exhaust gas will accumulate on the outer electrode,

while oxygen molecules from the reference gas will

accumulate on the inner electrode. This creates a voltag e

difference across the Nernst cell, bet ween the two

electrodes, which is the signal voltage to the ECM.

Legend

1 Outer Electrode

2 Inner Electrode

3 Heater Element

4 Oxygen Molecule (in exhaust stream)

5 Other Molecules (in exhaust stream)

6 Reference Gas (outside air)

7 Nernst Cell

V Signal Voltage Figure 6C1-1 – 42

When the fuel system is correctly operating in the closed-

loop mode, the oxygen sensor voltage output is rapidly

changing several times per second, fluctuatin g from

approximately 100mV (high oxygen co ntent – lean mixture)

to 900mV (low oxygen content – rich mixture). The transition

from rich to lean occurs quickly at about 450-500 mV (air

flow (A/F) ratio 14.7:1, or lambda = 1). Due to this, two-step

HO2S sensors are also known as switching type HO2S

sensors.

Legend

A Rich Mixture

B A/F Ratio 14.7:1 (Lambda = 1)

C Lean Mixture

D Sensor Voltage

Figure 6C1-1 – 43

Engine Management – V6 – General Information Page 6C1-1–48

Page 6C1-1–48

LSU 4.2 Wide-band Planar Heated Oxygen Sensors

The LSU 4.2 wide-band planar heated oxygen sensors have

six wires:

• The internal heater element supply, which has 12 V

continually applied whenever the ignition is on.

• Heater element ground – T he ECM applies pulse

width modulated (PWM) ground to the HO2S heater

control circuit to control the rate at which the sensor

heats up. This reduces the risk of the sensor bein g

damaged from heating up too quickl y under certain

conditions such as extreme cold temperatures. Once

the sensor has reached the desired operating

temperature, the ECM will monitor and continue to

maintain the sensor temperature.

• Output voltage.

• Sensor ground.

• Trim current.

• Pumping current.

Legend

1 Measuring Cell (Nernst cell and pump cell)

2 Double Protective Tube

3 Seal Ring

4 Seal Packing

5 Sensor Housing

6 Protective Sleeve

7 Contact Holder

8 Contact Clip

9 PTFE Sleeve (Teflon)

10 PTFE Shaped Sleeve

Figure 6C1-1 – 44

Engine Management – V6 – General Information Page 6C1-1–49

Page 6C1-1–49

Similar to the two-step HO2S, measurement is achi eved by

comparing the oxygen content of the exhaust gas to the

oxygen content of a reference gas. However, the way in

which the ECM calculates the exha ust oxygen content is

different, and results in a continual sig nal. This allows the

ECM to monitor not only whether the fuel mixture is rich or

lean, but exactly how rich or how lean. T he wide-band

HO2S is basically a two-step HO2S with the addition of a

pump cell.

The ECM applies a pump voltage acr oss the pump cell,

which causes oxygen to be pumpe d from the e xhaust gas

into or out of the diffusion gap through the diff usion barrier.

While monitoring the Nernst cell, the ECM varies the pump

current so the gas in the diffusion gap remains constant at

an A/F ratio of 14.7:1 (Nernst cell output of 450 mV).

Legend

1 Outer Electrode

2 Inner Electrode

3 Heater Element

4 Oxygen Molecule (in exhaust stream)

5 Other Molecules (in exhaust stream)

6 Reference Gas (outside air)

7 Nernst Cell

8 Pump Cell Electrode

9 Pump Cell Electrode

10 Pump Cell

11 Diffusion Gap

12 Porous Diffusion Barrier

A Pump Current

V Nernst Cell Voltage

Figure 6C1-1 – 45

If the exhaust gas is lean, the pump cell pumps oxygen to

the outside (positive pump current). If the exhaust gas is

rich, oxygen is pumped from the exhaust gas into the

diffusion gap (negative pump current). B y monitoring how

much it has to vary the pumping current, the ECM

determines the exact A/F ratio.

Legend

A Rich Mixture

B A/F Ratio 14.7:1 (Lambda = 1)

C Lean Mixture

D Sensor Current

Figure 6C1-1 – 46

Engine Management – V6 – General Information Page 6C1-1–50

Page 6C1-1–50

4.14 Ignition Coil and Spark Plug

Long-life platinum tip spark plugs are used which, along with

the ignition coil spark plug boot and spring, require

replacement at 120,000 kilometre service intervals. The

spark plugs, featuring a J-gap and a conical seat, do not

require inspection between services, and must not be re-

gapped.

Individual pencil-type ignition coils, one for each cylinder, are

mounted in the centre of the camshaft covers, and have

short boots connecting the coils directly to the spark plugs.

The pencil coil makes use of the space ava ilable in the spark

plug cavity in the cylinder head and cams haft cover. As a

pencil coil is always mou nted directly on to the spark plug,

no high-tension ignition leads are required, further enhancing

reliability.

Figure 6C1-1 – 47

Pencil coils operate similarly to other compact coils, however

due to their shape, the structure differs considerabl y.

The central rod core (1) consists of laminations of varying

widths, stacked in packs that are nearly spherical. A yoke

plate (2), made from layered electrical sheet steel, provides

the magnetic circuit. The primary winding (3) is located

around the secondary windi ng (4), which supports the core.

A printed circuit board, or driver module, (5) is located at the

top of the coil and controls the firing of the coil based on

input from the ECM.

The ECM is responsible for maintaining correct spark timing

and dwell for all driving conditions. The ECM calculates the

optimum spark parameters from information receiv ed from

the various sensors, and triggers the appropr iate ignition

module which then operates the coi l.

The ignition coil / modules are supplied with the following

circuits:

• Ignition feed circuit.

• Ground circuit.

• Ignition control circuit.

• Reference low circuit.

Figure 6C1-1 – 48

Engine Management – V6 – General Information Page 6C1-1–51

Page 6C1-1–51

4.15 Intake Air Temperature Sensor

The air intake temperature (AIT ) sensor is a thermistor,

which is a resistor that changes its resistance value based

on temperature.

The IAT sensor is part of the air mass sensor and is not a

serviceable item. The sensor is a negative temperature

coefficient (NTC) type. At low air intake air temperature, the

sensor produces a high sensor resistance, whilst at high air

intake air temperature the sensor produces a low

resistance.

Legend

A Temperature

B Resistance

The ECM provides a 5 V reference signal to the IAT and

monitors the return signal which enables it to calculate the

intake air temperature.

The ECM uses this signal to make corrections to the

operating parameters of the system b ased o n changes in air

intake temperature. Figure 6C1-1 – 49

Engine Management – V6 – General Information Page 6C1-1–52

Page 6C1-1–52

4.16 Intake Manifold Runner Control Valve

The intake manifold runner control (IMRC) valve is fitted int o the intake manifold of Alloytec 190 / High Output engines

only.

The purpose of the IMRC is to alter the length and volume of the intake manifold runners. Varying the intake manifold

takes advantage of the natural pulse / pressure waves occurring in the manifold that are created by the process of air

induction into the cylinders.

During induction with an open intake valve, a return pressure wave is generated in the intake manifold. At the open

(throttle) end of the intake manifold, the pressure wave encounters ambient, inactive air and is reflected back again,

returning in the direction of the intake valve.

The waves vary in length and speed, and are proportional to engine sp eed, and the length and volume of the intake

manifold runners. Therefore, at a given engine speed, the manifold can be tuned to increase the air charge into the

cylinders via the returning puls e waves to achieve higher engine torque. By using varying geometry intake manifold

tubing, there is a wider speed range in which the tuning can be effected.

The IMRC valve is supplied with ignition voltage via the

main relay and its operation is controlled by the ECM by

switching the ground circuit.

Referring to Figure 6C1-1 – 52, at lower engine speeds, the

valve flap is open (A), while at higher engine speeds, the

ECM commands the valve to close (B) by switching the

circuit to ground.

The characteristic flow in the manifold is altered by the

IMRC valve position.

Figure 6C1-1 – 50

Figure 6C1-1 – 51

Engine Management – V6 – General Information Page 6C1-1–53

Page 6C1-1–53

4.17 Knock Sensor

The knock sensor (KS) signal is used by the ECM to provide

optimum ignition timing while minimising engine knock or

detonation.

The ECM monitors the voltage of the left-hand (Bank 2)

sensor during the 45 degrees after cylinder 2, 4, or 6 has

fired and the voltage of the right-hand (Bank 1) sensor

during the 45 degrees after cylinder 1, 3, or 5 has fired.

If knock occurs in any of the cylinders, the ignition will be

retarded by three degrees for that particular cylinder. If the

knocking then stops, the ignition will be restored to what it

was before in steps of 0.75 degrees.

Should knocking continue in the same cylinder despite of

the ignition being retarded, the ECM will retard the ignition

an additional step of three degrees, and so on, up to a

maximum of 12.75 degrees. The ignition will also be

retarded at high ambient temperatures to counteract

knocking tendencies provoked by high intake air

temperatures.

Should either Bank 1 or Bank 2 sensor fail to work, or

should an open circuit occur, the ignitio n timing will then be

set at a default strategy that will retard the ignition much

more than normal.

Figure 6C1-1 – 52

The knock sensor is tuned to detect the frequency of the

vibration created by combustion knock. The vibration is

transferred to the knock sensor through the cylinder

block (1).

Inside the sensor is a mass (2) that is excited by this

vibration, and the mass exerts a compressive force onto a

piezo-ceramic element (3). The compressive force causes a

charge transfer inside the element, so that an AC voltage

appears across the two outer faces (4) of the element. The

amount of the AC voltage produced is proportional to the

amount of knock.

Figure 6C1-1 – 53

Engine Management – V6 – General Information Page 6C1-1–54

Page 6C1-1–54

4.18 Mass Air Flow Sensor

Air Intake System

The air intake system draws outside air through an air

cleaner assembly (1). The air is then routed throu gh a mass

air flow (MAF) sensor (2) and into the throttle body and

intake manifold. The air is then directed into the intake

manifold runners, through the c ylinder he ads and into the

cylinders.

An arrow marked on the body of the MAF sensor indicates

correct air flow direction. The arrow must point toward the

engine.

Figure 6C1-1 – 54

Mass Air Flow Sensor

A hot film type mass air flow (MAF) sensor is used which

measures the air mass inducted into th e engine, regardless

of the engine’s operating state . The MAF precisely

measures a portion of the total airflow and takes into

account the pulsation and reverse flows generated by the

engine’s inlet and exhaust valves.

Changes in intake air temperature have no effect on

measuring accuracy.

Figure 6C1-1 – 55

Engine Management – V6 – General Information Page 6C1-1–55

Page 6C1-1–55

Construction

Projecting into the MAF sensor bod y is the compact design

sensor assembly (1), which consists of:

• the sensor element (2),

• partial airflow measuring tube (3), and

• integrated evaluatio n electronics (4).

Figure 6C1-1 – 56

Operation

A diaphragm (1) on the sensor elem ent (2) is heated by a

centrally mounted heater resistor (3), which is held at a

constant temperature. The temperature drops sharpl y each

side of the heating zone.

Temperature of the diaphragm is registered to the

evaluation electronics by two temperature-dependent

resistors located on the upstream (4) and do wnstream (5)

side of the resistor.

With no air flow through the air flow measuring tube and

over the sensor element, the temperature ch aracteristic is

the same each side of the heating zone a nd the resistance

values are identical.

As air flows over the sensor element, the upstream resistor

value alters due to the cooling effect of the air flow. As the

air flows over the heating zone the air tempe r ature is

increased.

Figure 6C1-1 – 57

The air then passes over the downstream resistor and alters the resistance value, but as the air temperature is higher,

the value is different to the upstream resistor. This change i n temperature creates a temperature differential between the

two resistors.

It is this differential that is used to calculate the air mass flow, which is independent of ab solute temperature. The

differential is also directional, which means the MAF not only measures the mass of the incoming air, but also its

direction.

As the evaluation electronics are measuring the resistance differential between the resistors, the air mass flow for the

entire amount of air passing through the MAF is calculated and sent to the ECM as an analog signal of 0 – 5 V.

The ECM can also detect air flow that is inappropriate for a given operating condition based on the signal voltage, or a

signal that appears to be fixed based on the lack of normal signal fluctuations expected during engine operation.

Tech 2 can display the MAF value in grams per second (g/s). Values should change rather quickly on acceleration, b ut

should remain fairly stable at any given engine speed.

Engine Management – V6 – General Information Page 6C1-1–56

Page 6C1-1–56

4.19 Vehicle Speed Sensor – Manual

Transmission Only

The vehicle speed sensor (V SS) (1) operates on the Hall

sensing principle. The sensor contains a hall element which

operates in conjunction with a toothed trigg er wheel (2)

mounted on the transmission output shaft.

As the teeth on the gear trigger wheel passes the element,

magnetic flux affects a voltage in the Hall element. The

integrated circuit inside the sensor conditions the signal

generated by the Hall eleme nt to provide a rectangular wave

on / off signal to the ECM.

The ignition control relay applies battery voltage to the VSS,

and the ground circuit of the sensor is directly connected to

ground.

The engine control module (E CM) converts and outputs the

VSS signal to the instrument cluster assembly via a

dedicated circuit.

Figure 6C1-1 – 58

Engine Management – V6 – General Information Page 6C1-1–57

Page 6C1-1–57

5 Abbreviations and Glossary of

Terms

Abbreviations and terms used in this Section are listed below in alphabetical order with an explanation o f the

abbreviation or term.

Abbreviation Description

A/C Air-conditioning

AC Alternating Current – An electrical current where the polarity is constantly changing between positive and

negative

A/F Air / Fuel (A/F Ratio)

Analogue Signal An electrical signal that constantly varies in voltage within a given parameter

Barometric Pressure Barometric absolute pressure (atmospheric pressure)

CAN Controller Area Network – A type of serial data for communication between electronic devices.

Catalytic Converter A muffler-shaped device fi tted in the exhaust system, usually close to the engine. Through chemical reaction,

a catalytic converter converts harmful gases produced by the combustion process such as HC, CO, and NOx,

into environmentally safe water vapour, carbon dioxide, and nitrogen.

CKT Circuit

Closed Loop A fuel control mode of operation that uses the signal from the exhaust oxygen sensor(s), to control the air / fuel

ratio precisely at a 14.7 to 1 ratio. This allows maximum efficiency of the catalytic converter.

CO Carbon Monoxide. One of the gases produced by the engine combustion process.

DC Direct Current

Digital Signal An electrical signal that is either on or off.

DLC Data Link Connector. Used at the assembly plant to evaluate the engine management system. For service, it

allows the use of Tech 2 in performing system checks.

DLC Data Stream An output from the ECM initiated by Tech 2 and transmitted via the Data Link Connector(DLC).

DMM (10 MΩ) Digital Multimeter. A multipurpose meter that has capability of measuring voltage, current flow and resistance.

A digital multimeter has an input impedance of 10 MΩ (megohms), which means they draw very little power

from the device under test, they are very accurate and will not damage delicate electronic components

Driver An electronic device, usually a power transistor, that operates as an electrical switch.

DTC Diagnostic Trouble Code. If a fault occurs in the engine management system, the ECM may set a four digit

diagnostic trouble code (DTC) which represents the fault condition. Tech 2 is used to interface with the ECM

and access the DTC(s). The ECM may also operate the Check Powertrain icon in the instrument cluster multi

function display (Euro 2), or the Malfunction Indicator Lamp (MIL) in the instrument cluster (Euro 3).

Duty Cycle The time, in percentage, that a circuit is on versus off.

ECT Sensor Engine Coolant Temperature sensor. A device that provides a variable voltage to the ECM based on the

temperature of the engine coolant.

EEPROM Electrically Erasable Programmable Read Only Memory. A type of read only memory (ROM) that can be

electrically programmed, erased and reprogrammed using Tech 2. Also referred to as Flash Memory

EMI or Electrical

Noise An unwanted signal interfering with a required signal. A common example is the effect of high voltage power

lines on an AM radio.

Engine Braking A condition where the engine is used to slow the vehicle on closed throttle or low gear.

EPROM Erasable Programmable Read Only Memory. A type of Read Only Memory (ROM) that can be erased with

ultraviolet light and then reprogrammed.

ESD Electrostatic Discharge. The discharge of static electricity which has built up on an insulated material

EVAP Evaporative emission control system. Used to prevent fuel vapours from the fuel tank from entering into the

atmosphere. The vapours are stored in a canister that contains an activated charcoal element. The fuel

vapours are purged from the canister into the manifold to be burned in the engine.

GM LAN General Motors Local Area Network - A type of serial data for communication between electronic devices.

Fuse A thin metal strip which melts when excessive current flows through it, creating an open circuit and protecting

a circuit from damage.

HC Hydrocarbon. Result of unburned fuel produced by incomplete combustion.

Heavy Throttle Approximately 3/4 of accelerator pedal travel (75% throttle position)

IAT Sensor Intake Air Temperature sensor. A device that provides a variable voltage to the ECM based on the

temperature of air entering the intake system.

Ideal Mixture The air / fuel ratio which provides the best performance, while maintaining maximum conversion of exhaust

emissions, typically 14.7 to 1 on spark ignition engines

IGN Ignition

Inputs Information from sensors (MAF, TP, etc.) and switches (A/C request, etc.) used by the ECM to determine how

to control its outputs.

Engine Management – V6 – General Information Page 6C1-1–58

Page 6C1-1–58

Abbreviation Description

Intermittent An electrical signal that occurs now and then; not continuously. In electrical circuits, refers to occasional open,

short, or ground in a circuit

Light Throttle Approximately 1/4 of accelerator pedal travel (25% throttle position)

Low A voltage less than a specific threshold. Operates the same as a ground and may, or may not, be connected

to chassis ground.

MAF Sensor Mass Air Flow Sensor. A device that provides a variable voltage to the ECM based on the amount of air flow

entering in the intake system.

Medium Throttle Approximately 1/2 of accelerator pedal travel (50% throttle position)

MIL The Malfunction Indicator Lamp is activated by the ECM whenever an emissions related problem exists, to

alert the driver that attention to the engine management system is required.

N.C Normally Closed. Switch contacts that are closed when they are in the normal operating position

N.O Normally Open. Switch contacts that are normally open when in the normal operating position

NOx Nitrogen Oxide. One of the pollutants found in spark ignition engine exhaust that is formed from normal

combustion and increases in severity with combustion temperature.

O2 Sensor Oxygen Sensor. A device located in the exhaust system that provides a variable voltage to the ECM based on

the oxygen content of exhaust gas.

May also include a heating circuit to provide faster initial warm-up (HO2 sensor).

OBD On Board Diagnostic

Open Loop ECM control of the fuel control system without the use of the oxygen sensor signal.

Output Functions that are controlled by the ECM, typically these can include solenoids and relays, etc.

ECM Engine Control Module. An electronic device which controls the engine management system.

ECU Electronic Control Unit. An electronic device which controls specific system functions

PCV Positive Crankcase Ventilation. Method of reburning crankcase fumes rather than passing them directly into

the atmosphere

PIM Powertrain Interface Module – The PIM acts as a communication translator between the ECM and other on-

board controllers that use a different serial data protocol.

PM Permanent Magnet

PWM Pulse Width Modulated. A digital signal turned on and off for a percentage of available cycle time. A signal that

is 30% on and 70% of would be termed a 30% on PWM signal.

Quad Driver A transistor in the ECM capable of operating four separate outputs. Outputs can be either on-off or pulse width

modulated.

RAM Random Access Memory. A microprocessor can write into or read from this memory as needed. This memory

is volatile and needs a constant power supply to be retained. If the power is lost or removed, RAM data is lost.

r.p.m. Revolutions Per Minute

Serial Data Serial data is a series of rapidly changing voltage signals pulsed from high to low. These signals are typically

5 V (UART), 7 V (Class II), and 12 or 0 V (high or low) and are transmitted through a wire often referred to as

the Serial Data Circuit.

SFI Sequential Fuel Injection. Method of injecting fuel into the engine one cylinder at a time in relation to the

engines firing order.

Solenoid An electromagnetic coil which creates a magnetic field when current is applied, causing a plunger or ball to

move.

Switch Device to opens and close a circuit, thereby controlling current flow.

Tech 2 Tech 2 is a peripheral device that aids in the diagnosis and repair of electronic systems such as engine

management, transmission control, ABS, etc. Tech 2 connects to the vehicle’s Data Link Connector (DLC).

TP Sensor Throttle Position sensor. A device that provides a variable voltage to the ECM based on the position of the

throttle plate.

Vacuum – manifold Vacuum sourced downstream of the throttle plate.

Vacuum – ported Vacuum sourced upstream of the throttle plate.

VSS Vehicle Speed Sensor. A permanent magnet type device that provides a digital voltage to the ECM.

UART Universal Asynchronous Receive and Transmit. A type of serial data for communicati on between electronic

devices.

WOT Wide Open Throttle – Full travel of the accelerator pedal (100% throttle position).