Engine Control - Description & Operation Land Rover Discovery L318

VEHICLE IDENTIFICATION

VEHICLE IDENTIFICATION

COMPONENT LOCATIONS

For engine management control component locations (Scheme 18)and (Scheme 19).

Scheme 18

Scheme 19

ENGINE MANAGEMENT BLOCK DIAGRAM

For engine management block diagram (Scheme 20)

Scheme 20

GENERAL

The V8 engine is equipped with the Bosch Motronic M5.2.1 engine management system. This system is a sequential multiport fuel injection system controlled by an Engine Control Module (ECM).

A single ECM is used for the control of the existing 4.0 liter engine and the new 4.6 liter engine introduced with 2003 model year vehicles for the NAS market only. The ECM contains the tunes for both engines variants. When the ECM is replaced, TestBook/T4 must be used to select the correct tune to match the engine fitment.

The ECM has On Board Diagnostic (OBD) strategies as required by various market legislative bodies. To meet these requirements the system monitors and reports on any faults that cause excessive exhaust emissions.

In markets that mandate OBD, the ECM monitors performance of the engine for misfires, catalyst efficiency, exhaust leaks and evaporative control loss. If a fault occurs, the ECM stores the relevant fault code and warns the driver of component failure by illuminating the Malfunction Indicator Light in the instrument pack.

In markets where OBD is not mandatory, the ECM will still monitor performance of the engine and store the fault code, but will NOT illuminate the Malfunction Indicator Light.

The ECM uses input and output information from its sensors and actuators to control the following engine conditions

1. Fuel Quantity.
2. Closed Loop Fuelling
3. Open Loop Fuelling
4. Ignition Timing
5. Knock Control
6. Idle Speed Control
7. Emission Control
8. On-Board Diagnostic (OBD) Where Applicable
9. Vehicle Immobilization
10. Misfire Detection (Where Applicable)
11. Vehicle Speed Signal
12. Rough Road Signal (Where Applicable)
13. Low Fuel Level Signal (Where Applicable)
14. Coolant Temperature Gauge Signal

The ECM processes sensor information from the following input sources

1. Ignition Switch (Position II)
2. Crankshaft Speed & Position Sensor
3. Camshaft Position Sensor
4. Engine Coolant Temperature Sensor
5. Mass Air Flow Sensor
6. Intake Air Temperature Sensor
7. Knock Sensor
8. Throttle Position Sensor
9. Heated Oxygen Sensors
10. High/Low Ratio Switch
11. Fuel Tank Pressure Sensor (Where Fitted)
12. Thermostat Monitoring Sensor (Where Fitted)

The ECM controls the following outputs

1. Fuel Injectors (1 Per Cylinder)
2. Ignition Coils/High Tension Leads/Spark Plugs
3. Fuel Pump Relay
4. Idle Air Control Valve
5. Heated Oxygen Sensors
6. EVAP Canister Purge Valve
7. EVAP Canister Vent Solenoid (CVS) Valve (Where Fitted)
8. Malfunction Indicator Lamp (MIL)/Service Engine Soon Lamp (Where Fitted)
9. Hill Descent Control (Via SLABS Interface)
10. EVAP System Fuel Leak Detection Pump (Where Fitted)
11. Secondary Air Injection Pump (Where Fitted)

The ECM also interfaces with the following

1. Diagnostics Via Diagnostic Connector With Testbook/T4
2. Controller Area Network (CAN) Link To EAT ECU
3. Air Conditioning System
4. Self Levelling & Anti-Lock Braking System (SLABS) ECU
5. Immobilization System Via The Body Control Unit (BCU)
6. Instrument Cluster
7. Cruise Control ECU
8. Active Cornering Enhancement (ACE) ECU

Engine Control Module (ECM)

The Engine Control Module (ECM) is located on the RH side A post below the face panel inside the vehicle. (Scheme 21) It has a cast aluminum case and is mounted on a bracket. The ECM has 5 independent connectors totalling 134 pins.

Scheme 21

The ECM is available in 4 variants

1. NAS (North Americian Version)
2. NAS Low Emission Vehicles
3. UK/Europe/Japan/Australia
4. ROW/Gulf

The ECM uses a FLASH electronic erasable programmable read only memory (EEPROM). This enables the ECM to be externally configured, to ensure that the ECM can be updated with any new information, this also allows the ECM to be configured with market specific data. Textbook/T4 must be used to configure replacement ECM's. The ECM can be reprogrammed, using TestBook/T4, with new engine tunes up to 16 times to meet changing specifications and legislation. The current engine tune data can be accessed and read using TestBook/T4.

The ECM memorizes the positions of the crankshaft and the camshaft when the engine has stopped via the CKP and CMP sensors. This allows immediate sequential fuel injection and ignition timing during cranking. This information is lost if battery voltage is too low (i.e. flat battery). So the facility will be disabled for the first engine start.

ECM Input/Output

The ECM has various sensors fitted to the engine to allow it to monitor engine condition. The ECM processes these signals and decides what actions to carry out to maintain optimum engine operation by comparing the information from these signals to mapped data within its memory.

Connector 1 - C0634

This connector contains 9 pins and is used primarily for ECM power input and earth. (Scheme 22) The ECM requires a permanent battery supply, if this permanent feed is lost i.e. the battery discharges or is disconnected the ECM will lose its adapted values and its Diagnostic Trouble Codes (DTC). These adapted values are a vital part of the engine management's rolling adaptive strategy. Without an adaptive strategy, driveability, performance, emission control, and fuel consumption are adversely affected. The ECM can be damaged by high voltage inputs, so care must be taken when removing and replacing the ECM.

Scheme 22

Connector 2 - C0635

This connector contains 24 pins and is primarily used for Heated Oxygen Sensors (HO2S) control and earth. (Scheme 23) The HO2S sensors require a heater circuit to assist in heating the tip of the sensors to enable closed loop fuelling to be implemented quickly after cold starting.

Scheme 23

Connector 3 - C0636

This connector contains 52 pins and is used for most sensor and actuator inputs and outputs. (Scheme 24)and (Scheme 25). Sensor and actuator control is vital to ensure that the ECM maintains adaptive strategy

Scheme 24

Scheme 25

Connector 4 - C0637

This connector contains 40 pins and facilitates use of TestBook/T4 via the Diagnostic connector. (Scheme 26)and (Scheme 27). Also contained in this connector is the Malfunction Indicator Lamp (MIL), this instrument panel lamp informs the driver of concerns within the engine management system.

Scheme 26

Scheme 27

Connector 5 - C0638

This connector contains 9 pins and is used to control the ignition system. (Scheme 28) The ignition coils are supplied with power and a switching earth completes the circuit.

Scheme 28

Crankshaft Speed & Position (CKP) Sensor

The CKP sensor is located towards the rear of the engine below cylinder number 7, with its tip adjacent to the outer circumference of the flywheel. (Scheme 29) The CKP sensor is the most important sensor on the vehicle and without its signal the engine will not run. The signal produced by the CKP sensor allows the ECM to determine crankshaft angle and speed of rotation. The ECM uses this information to calculate ignition timing and fuel injection timing.

The CKP sensor works as a variable reluctance sensor. It uses an electromagnet and a reluctor ring to generate a signal. As the reluctor ring passes the tip of the CKP sensor the magnetic field produced by the sensor is cut and then re-instated. The ECM measures the signal as an AC voltage.

The output voltage varies in proportion to engine speed. The reluctor ring has a set tooth pattern, 60 teeth are spaced at 6° intervals and are 3° wide, two teeth are removed to provide a reference mark at 60° BTDC for number 1 cylinder. There is no back up strategy or limp home facility if this sensor fails, the engine does not run.

Scheme 29

CKP Sensor Input/Output

Because of the nature of its operation the CKP sensor does not require any electrical input source. The CKP sensor is a 3 pin variable reluctance sensor generating its own electrical output. The 2 output sources from the sensor are grounded via pin 46 of connector C0636 of the ECM and sensor output is via pin 32 of connector C0636 of the ECM. This output is in the form of an AC voltage waveform. The 3rd pin is used by the ECM as an earth screen, this screen protects the integrity of the CKP sensor signal to ensure that outside electrical interference is eliminated, it is controlled via pin 45 of connector C0636 of the ECM. The AC voltage generated from the CKP sensor is relative to engine speed.

The above readings are dependent upon correct air gap between the tip of the CKP sensor and the passing teeth of the reluctor ring. (Scheme 30) The correct air gap between the tip of the CKP sensor and the passing teeth of the reluctor ring can be set by the correct fitting of a spacer as follows

1. 9.2-mm spacer for vehicles with manual gearbox fitted.
2. 18-mm spacer for vehicles with automatic gearbox fitted.

Scheme 30

It is vital that the correct air gap is maintained, if the air gap becomes too wide the CKP signal becomes too weak, causing possible engine misfires to occur.

The CKP sensor can fail the following ways or supply incorrect signal

1. Sensor assembly loose
2. Incorrect spacer fitted
3. Sensor open circuit
4. Sensor short circuit
5. Incorrect fitting and integrity of the sensor.
6. Water ingress at sensor connector.
7. ECM unable to detect the software reference point.
8. Ferrous contamination of crank sensor pin/reluctor.

In the event of a CKP sensor signal failure any of the following symptoms may be observed

1. Engine cranks but fails to start.
2. MIL remains on at all times.
3. Engine misfires (CKP sensor incorrectly fitted).
4. Engine runs roughly or even stalls (CKP sensor incorrectly fitted).
5. Tachometer fails to work.
6. Flywheel adaption reset - ferrous contamination.

If the CKP sensor fails while the engine is running the engine will suddenly stall, this is because the CKP sensor has no backup strategy. If this happens the ECM will produce a fault code that it can store in its memory. If the engine is not running when the CKP sensor fails, the vehicle will crank but will be unlikely to start, and no fault code will be generated. In this instance the MIL lamp will remain illuminated and the tachometer will fail to read.

It is vital that the CKP sensor output wires are not reversed (i.e. the connector is fitted incorrectly) as this will cause a 3° advance in ignition timing. This happens because the ECM uses the falling edge of the signal waveform as its reference or timing point for each passing tooth on the reluctor.

Whenever a new crankshaft position sensor is fitted or the flywheel is removed, the adaptive values will have to be reset, using TestBook/T4.

Should a malfunction of the component occur, the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 31)

Scheme 31

Camshaft Position (CMP) Sensor

The CMP sensor is located on the front of the engine, above and behind the crankshaft pulley. (Scheme 32) The CMP sensor is a Hall effect sensor producing four pulses for every two crankshaft revolutions. The sensor is positioned close to the camshaft gear wheel, the gear wheel has four slots machined at 90° intervals. This allows the ECM to recognize 4 individual cylinders every camshaft revolution or all 8 cylinders every crankshaft revolution.

The CMP sensor Hall effect works as a magnetic switch. It switches battery voltage on or off depending on the position of the camshaft gear wheel in relationship to the sensor.

The ECM uses this signal for cylinder recognition to control sequential fuel injection, engine knock and diagnostic purposes.

Scheme 32

CMP Sensor Input/Output

Electrical input to the camshaft position sensor is from fuse 2 located in engine compartment fuse box. One output is sensor earth, the other is the signal output to the ECM via pin 20 of connector C0636.

The CMP sensor can fail the following ways or supply incorrect signal

1. Sensor open circuit.
2. Short circuit to vehicle battery supply.
3. Short circuit to vehicle earth.
4. Incorrect fitting of the sensor.
5. Excessive camshaft gear wheel tolerance.
6. Excessive camshaft endfloat.
7. Camshaft and crankshaft misalignment.
8. Speed signal correlation with CKP sensor signal.
9. Cam wheel magnetized/residual magnetism.

In the event of a CMP sensor signal failure any of the following symptoms may be observed

1. Ignition timing reverts to default values from ECM memory.
2. Loss of cylinder correction.
3. Loss of active knock control.
4. Loss of active knock control diagnostics.
5. Loss of cylinder identification for misfire diagnostics.
6. Loss of quick synchronization of crankshaft and camshaft for cranking/start up.
7. Fuel injection could be 360° out of phase.
8. Front HO2S sensor ageing period diagnostic disabled (NAS only).

Should a malfunction of the component occur the following fault code may be evident and can be retrieved by TestBook/T4. (Scheme 33) The fault condition has to be detected for more than 100 cam pulses (25 revolutions) when the engine speed is greater than 500 rev/min.

Scheme 33

Engine Coolant Temperature (ECT) Sensor

The ECT sensor is located at the front of the engine adjacent to the coolant outlet pipe. (Scheme 34) The ECT sensor forms a vital part of the ECM operating strategy, and therefore the optimum control of the running of the engine. Richer air/fuel ratio is required at lower coolant temperatures such as cold starting. Coolant temperature information from the ECT sensor is also vital to enable the ECM to weaken the air/fuel mixture as temperature rises to maintain low emissions and optimum performance.

Scheme 34

For NAS vehicles with secondary air injection, the signal from the ECT sensor is monitored at engine start, to determine whether the conditions are cold enough to warrant secondary air injection to be employed. The ECT sensor is then monitored to switch off the secondary air injection when the required engine coolant temperature has been attained.

The ECT works as a Negative Temperature Coefficient (NTC) sensor. As temperature rises, the resistance in the sensor decreases, as temperature decreases, the resistance in the sensor increases. The ECT sensor forms part of a voltage divider chain with a pull up resistor within the ECM. Consequently as the ECT sensor resistance changes, the analogue voltage at the input signal from the ECT sensor to the ECM will be adjusted which corresponds to the temperature of the engine coolant. With this information, the ECM can implement the correct strategies for cold start, warm up etc. The ECM supplies the instrument cluster with a pulse width modulated (PWM) coolant temperature signal to drive the temperature gauge.

Input/Output

The electrical input and output to and from the ECT sensor are reference voltage and sensor earth. The ECM provides the ECT sensor with a 5 volt reference via pin 22 of connector C0636 of the ECM, and earth via pin 21 of connector C0636 of the ECM. The normal operating parameters of the ECT sensor are as follows. (Scheme 35)

Scheme 35

Should the sensor fail the ECM has a back up strategy that uses a changing default value during warm up based on the signal from the inlet air temperature sensor. When the strategy default value reaches 60°C (140°F), the ECM implements a fixed default value of 85°C (185°F). It will also illuminate the MIL.

The ECT sensor can fail the following ways or supply incorrect signal

1. Sensor open circuit.
2. Short circuit to vehicle supply.
3. Short circuit to earth.
4. Incorrect mechanical fitting.
5. Signal fixed above 40°C (140°F) will not be detected.
6. Signal fixed below 40°C (140°F) will be detected.

In the event of an ECT sensor signal failure any of the following symptoms may be observed

1. Difficult cold start.
2. Difficult hot start.
3. Driveability concern.
4. MIL illuminated.
5. Instrument cluster temperature warning lamp illuminated.
6. Temperature gauge reads excessively hot.
7. Temperature gauge reads excessively cold.
8. Cooling fan will not run.

There are three types of ECT sensor diagnostic checks

1. The ECT sensor signal is within limits, but is inaccurate - the engine has to be running and the signal indicates a coolant temperature below 40°C (104°F). The signal differs too much from the coolant temperature model for longer than 2.53 seconds.
2. The ECT sensor signal is greater than the maximum threshold value - the ECM has to be powered up to perform the diagnostic, but the engine does not need to be running.
3. The ECT sensor signal is less than the minimum threshold value - the ECM has to be powered up to perform the diagnostic, but the engine does not need to be running.

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook/T4.

Scheme 36

Thermostat Monitoring Sensor

The thermostat monitoring sensor is located in the radiator, adjacent the bottom hose. (Scheme 37) The ECM compares the temperature measured by the thermostat monitoring sensor to the temperature measured by the ECT sensor. If the difference between the two readings is too great, the ECM determines the thermostat is stuck. In this case, the ECM registers a fault code in its memory.

Scheme 37

The thermostat monitoring sensor works as a Negative Temperature Coefficient (NTC) sensor. As temperature rises, the resistance in the sensor decreases, as temperature decreases, the resistance in the sensor increases. With this information, the ECM is able to monitor the performance of the thermostat. The normal operating parameters of the thermostat monitoring sensor are as follows. (Scheme 38)

Scheme 38

The ECM provides the thermostat monitoring sensor with a 5 volt reference via pin 21 of connector C0635 of the ECM, and an earth via pin 5 of connector C0635 of the ECM.

There are three types of thermostat monitoring sensor diagnostic checks

1. Sensor signal is above maximum threshold. For the ECM to register this as a fault, and illuminate the MIL, the temperature registered by the thermostat monitoring sensor must be above 140°C (284°F) for more than 1 second.
2. Sensor signal is below minimum threshold. For the ECM to register this as a fault, and illuminate the MIL, the temperature registered by the thermostat monitoring sensor must be below -33°C (-27°F) for more than 1 second, while the inlet air temperature reading is greater than -32°C (-25°F).
3. Signal difference between ECT sensor and thermostat monitoring sensor is below maximum threshold. For the ECM to register this as a fault, and illuminate the MIL, the following conditions must exist: No maximum or minimum threshold signal faults exist. No faults are recorded against the thermostat monitoring sensor or vehicle speed signal. Engine not in idle speed control. Fuel cut-off not active. Engine speed is greater than 400 RPM. Road speed is greater than 0 mph. Integrated mass air flow from engine start to fuel cut-off is greater than set value (between 3 kg and 10 kg dependent upon engine coolant temperature at engine start). Engine coolant temperature at engine start is between 9°C and 39°C (48°F and 102°F). High range is selected. Delay time before thermostat monitoring is enabled is between set limits (between 50 and 500 seconds dependent upon engine coolant temperature at engine start). Engine coolant temperature is greater than 90°C (194°F). The difference between the ECT sensor reading and the thermostat monitoring sensor reading is less than 39°C (102°F).

Should a malfunction occur, the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 39)

Scheme 39

MAF/IAT Sensor

The MAF/IAT sensors are combined into a single unit and located between the air filter housing and the inlet manifold. (Scheme 40)

The ECM receives input signals from the MAF/IAT sensor to calculate the mass of air flowing into the engine inlet manifold.

Scheme 40

The MAF sensor has both electrical input and output. Input to the MAF sensor comes from two different sources. Battery voltage is supplied to the MAF sensor via fuse 2 of the engine compartment fuse box. The MAF sensor also utilizes a 5 volt reference input via pin 7 of connector C0636 of the ECM. The MAF sensor output voltage is measured via pin 23 of connector C0636 of the ECM.

The IAT sensor has only electrical output. Output from the IAT sensor is measured at pin 34 of connector C0636 of the ECM, this is a variable voltage/resistance measured by the sensor to provide air temperature information to the ECM.

The MAF/IAT sensor share the same sensor earth. Sensor earth is via pin 9 of connector C0636 of the ECM.

The MAF/IAT sensor and its connector has silver plated terminals for its low current signals to protect against corrosion. DO NOT apply 12V to the 5V supply, as this will destroy the internal circuitry. The MAF/IAT sensor should not be dropped or roughly handled and should be kept free from contamination.

MASS AIR FLOW (MAF) SENSOR

The MAF sensor utilizes a "hot film" element contained in the air intake duct to monitor the mass of the air flow being drawn into the engine. The MAF sensor contains two sensing elements, one element is controlled at ambient temperature, e.g. 25°C (77°F), while the other is heated to 200°C (360°F) above the ambient temperature, e.g. 225°C (437°F).

When the intake air passes the heated element, it cools it down, so lowering the resistance of the hot film element. In order to maintain the same temperature, the circuit to the heated element has to supply more current. The change in current causes a corresponding change in potential difference to be detected in the monitoring circuit. This change is supplied to the ECM as a voltage between 0 and 5V, where it is processed by the ECM's internal mapping to interpret the data as a measure of the mass of air flow.

The measured air mass flow is used by the ECM to determine the fuel quantity to be injected in order to maintain the stoiciometric air/fuel mixture for optimum engine performance and low emissions.

Normal operating parameters of the MAF sensor are as follows. (Scheme 41)

Scheme 41

If the MAF sensor fails, the ECM implements a back up strategy which is based on throttle angle. Poor throttle response and reduced performance will result.

The MAF sensor can fail the following ways or supply incorrect signal

1. Sensor open circuit.
2. Short circuit to vehicle supply.
3. Short circuit to vehicle earth.
4. Contaminated sensor element.
5. Damaged sensor element.
6. Air leak after the MAF sensor.
7. Inlet air restriction.
8. Resistance in wiring harness causing signal offset.

In the event of a MAF sensor signal failure any of the following symptoms may be observed

1. During driving engine rev/min may dip, before recovering.
2. Difficult starting.
3. Engine stalls after starting.
4. Delayed throttle response.
5. Emissions control inoperative.
6. Idle speed control inoperative.
7. Reduced engine performance.
8. MAF sensor signal offset.

There are two types of MAF sensor diagnostic check

1. The MAF sensor signal is less than the minimum threshold for specific speed range - the engine must have exceeded 200 rev/min for longer than 300 ms and remain above 400 rev/min. The signal must be less than the threshold mapped against engine speed for longer than 500 ms.
2. The MAF sensor signal is greater than the maximum threshold for specific speed range - the engine must have exceeded 200 rev/min for longer than 10 ms. The signal must be greater than the threshold mapped against engine speed for longer than 300 ms.

If the MAF sensor fails the following fault codes will be produced and can be retrieved by TestBook/T4. (Scheme 42)

Scheme 42

INTAKE AIR TEMPERATURE (IAT) SENSOR

The intake air temperature (IAT) sensor utilizes a thermistor with a negative temperature coefficient (NTC); as temperature rises, the thermistor resistance decreases. The change in resistance causes a change in input voltage at the ECM. The ECM converts the voltage value it receives to provide an indication of the temperature of the inlet air.

Normal operating parameters of the IAT sensor are as follows. (Scheme 43)

Scheme 43

Should the IAT sensor fail, the ECM defaults to an assumed air temperature of 45°C (113°F).

The IAT sensor can fail the following ways or supply incorrect signal

1. Sensor open circuit.
2. Short circuit to vehicle battery supply.
3. Short circuit to vehicle earth.
4. Increased sensor resistance.
5. Damaged sensor element.

In the event of an IAT sensor signal failure any of the following symptoms may be observed

1. Adaptive fuelling disabled.
2. Idle speed adaption disabled.
3. Catalyst monitoring affected due to exhaust temperature model.
4. Idle speed actuator test disabled.
5. Warm up ignition angle affected.
6. Condenser fan hot restart inhibited.

There are two types of IAT sensor diagnostic checks

1. The IAT sensor signal is less than the minimum threshold - the engine has to have been running for longer than 180 seconds, and idle speed control must have been operational for longer than 10 seconds. No fuel cut off is active. The IAT sensor signal must be less than -35°C (-31°F) for longer than 200 ms.
2. The IAT sensor signal is greater than the maximum threshold - the ECM has to be powered up (engine does not need to be running), and the signal must be greater than 140°C (284°F) for longer than 200 ms.

If the IAT sensor fails the following fault codes will be produced and can be retrieved by TestBook/T4. (Scheme 44)

Scheme 44

AIR INTAKE DUCT - GULF MODELS FROM 2000MY

The density of the intake air is partly dependent on altitude and temperature. Hot air has a lower density than cold air; consequently in hot climates, the low air density can result in low power due to low volumetric efficiency.

In order to improve engine performance, Gulf specification models from 2000MY have a secondary air intake duct which is located under the front left inner wing of the vehicle. (Scheme 45) Cooler air from the side of the vehicle is routed through the duct to the air cleaner, where it combines with air entering via the front grille.

In addition to the secondary air duct, the vehicles are fitted with a larger front grille and have larger cooling and condenser fans.

The MAF/IAT sensor, air cleaner and air cleaner duct are encased in insulation bags to help keep the intake air cool and so increase the mass of air entering the engine intake manifold.

The air cleaner includes a cyclone filter and also a dump valve in the bottom of the unit. Sand and dust particles which are carried into the air cleaner with the air flow are automatically expunged via the dump valve.

Scheme 45

Throttle Position (TP) Sensor

The TP sensor is located on the throttle body assembly in the engine compartment. (Scheme 46) The ECM is able to determine the position of the throttle plate and the rate of change of its angle. The ECM processes the signal received from the TP sensor.

Scheme 46

The TP sensor consists of a resistance track and a sliding contact connected to the throttle plate assembly. As the throttle is opened and closed the sliding contact moves along the resistance track to change the output voltage of the sensor. The ECM determines throttle plate position by processing this output voltage. The connection of the sensor to the throttle plate assembly is via a shaft.

The ECM is able to determine the closed throttle position, this enables the TP sensor to be fitted without the need for prior adjustment. The TP sensor signal has input into the ECM's fuelling strategy and also to determine closed throttle position for idle speed control. The TP sensor also supplies the ECM with information to enable the overrun fuel cut off strategy to be implemented. When the ECM receives closed throttle information from the TP sensor it closes the injectors for the duration of the closed throttle time.

The TP sensor signal is also used by the Electronic Automatic Transmission (EAT) ECU to determine the correct point for gear shifts and acceleration kickdown. The ECM also supplies the SLABS ECU with this TP sensor information as a PWM signal.

The TP sensor has electrical input and output. Input is a 5 volt supply via pin 10 of connector C0636 of the ECM. The signal output is via pin 24 of connector C0636 and is a varying voltage, less than 0.5V (closed throttle) and greater than 4.5V (wide open throttle) depending on throttle plate position. The TP sensor earth is via pin 25 of connector C0636 of the ECM, this acts as a screen to protect the integrity of the TP sensor signal.

The connector and sensor terminals are gold plated for corrosion and temperature resistance, care must be exercised while probing the connector and sensor terminals.

If the TP sensor signal fails, the ECM uses a default value derived from engine load and speed.

The TP sensor can fail the following ways or supply incorrect signal

1. Sensor open circuit.
2. Short circuit to vehicle supply.
3. Short circuit to vehicle earth.
4. Signal out of parameters.
5. Blocked air filter (load monitoring, ratio of the TP sensor to air flow).
6. Restriction in air inlet (load monitoring, ratio of the TP sensor to air flow).
7. Vacuum leak.

In the event of a TP sensor signal failure any of the following symptoms may be observed

1. Engine performance concern.
2. Delayed throttle response.
3. Failure of emission control.
4. Closed loop idle speed control inoperative.
5. Automatic gearbox kickdown inoperative.
6. Incorrect altitude adaptation.
7. MIL illuminated (NAS only).

There are three throttle position sensor diagnostic checks

1. TP sensor signal is greater than the maximum threshold value - the engine speed must be greater than 400 rev/min for longer than 2 seconds and the signal must be greater than 96% for longer than 50 ms.
2. TP sensor signal is less than the minimum threshold - the engine speed must be greater than 400 rev/min for longer than 2 seconds and the signal must be less than 4% for longer than 50 ms.
3. Ratio of throttle position to mass of air flow - the calculated throttle angle must be outside limits when the engine speed is between 800 rev/min and 4000 rev/min, the engine load is between 2 and 6.5 and the coolant temperature is above -10°C (14°F).

Should a malfunction of the TP sensor occur the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 47)

Scheme 47

Heated Oxygen Sensors (HO2S)

The market requirement dictates how many HO2S are fitted to the vehicle

1. 4 sensors are fitted to all NAS and EU-3 vehicles.
2. 2 sensors fitted to all UK, European, Australia and Japanese pre EU-3 specification vehicles.
3. No sensors fitted to ROW vehicles.

The HO2S monitor the oxygen content of the exhaust gases. By positioning the sensors one for each bank upstream of the catalytic converter in the exhaust pipe, the ECM can control fuelling on each bank independently of the other. (Scheme 48) This allows greater control of the air/fuel ratio and maintains optimum catalyst efficiency. On NAS vehicles the ECM also uses two HO2S positioned downstream of the catalytic converters in the exhaust pipe to monitor catalytic converter efficiency. The ECM is able to achieve this by comparing the values of the upstream HO2S and the down stream sensor for the same bank. These comparative values form part of the ECM OBD strategy.

Scheme 48

The HO2S uses zirconium contained in a galvanic cell surrounded by a gas permeable ceramic, this produces an output voltage proportional to the ratio difference between the oxygen in the exhaust gases and to the ambient oxygen.

The HO2S operates at approximately 350°C (662°F). To achieve this temperature the HO2S incorporate a heating element which is controlled by a PWM signal from the ECM. The elements are activated immediately after engine starts and also under low engine load conditions when the exhaust gas temperature is insufficient to maintain the required HO2S temperature. If the heater fails, the ECM will not allow closed loop fuelling to be implemented until the sensor has achieved the required temperature.

This value equates to an HO2S output of 450 to 500 mV. A richer mixture can be shown as lambda = 0.97, this pushes the HO2S output voltage towards 1000 mV. A leaner mixture can be shown as lambda = 1.10, this pushes the HO2S output voltage towards 100 mV.

From cold start, the ECM runs an open loop fuelling strategy. The ECM keeps this strategy in place until the HO2S is at a working temperature of 350°C (662°F). At this point the ECM starts to receive HO2S information and it can then switch into closed loop fuelling as part of its adaptive strategy. The maximum working temperature of the tip of the HO2S is 930°C (1706°F), temperatures above this will damage the sensor.

HO2S age with use, this increases their response time to switch from rich to lean and from lean to rich. This can lead to increased exhaust emissions over a period of time. The switching time of the upstream sensors are monitored by the ECM. If a pre-determined threshold is exceeded, a failure is detected and the MIL illuminated.

The upstream and downstream HO2S are color coded to prevent incorrect fitting. The tips of the upstream sensors are physically different to the tips of the downstream sensors.

The HO2S are color coded as follows

1. Upstream sensors (both banks) - Orange.
2. Downstream sensors (both banks) - Grey.

The four HO2S have a direct battery supply to the heater via fuse 2 located in the engine compartment fuse box.

The heater is driven by the ECM providing an earth path for the circuit as follows

1. Upstream LH bank via pin 19 of connector C0635 of the ECM.
2. Upstream RH bank via pin 13 of connector C0635 of the ECM.
3. Downstream LH bank via pin 7 of connector C0635 of the ECM.
4. Downstream RH bank via pin 1 of connector C0635 of the ECM.

The HO2S output signal is measured by the ECM as follows

1. Upstream LH bank via pin 15 of connector C0635 of the ECM.
2. Upstream RH bank via pin 16 of connector C0635 of the ECM.
3. Downstream LH bank via pin 17 of connector C0635 of the ECM.
4. Downstream RH bank via pin 14 of connector C0635 of the ECM.

The HO2S earth path for the signal is supplied by the ECM as follows

1. Upstream LH bank via pin 9 of connector C0635 of the ECM.
2. Upstream RH bank via pin 10 of connector C0635 of the ECM.
3. Downstream LH bank via pin 11 of connector C0635 of the ECM.
4. Downstream RH bank via pin 8 of connector C0635 of the ECM.

The HO2S voltage is difficult to measure using a multimeter, the output can be monitored using TestBook/T4. A rich mixture would read 500 to 1000 mV, a weak mixture would read 100 mV to 500 mV, the reading should switch from rich to weak. The open loop default voltage is 450 mV, this is used by the ECM to set the air/fuel ratio until the tip of the HO2S reaches operating temperature.

The HO2S can fail the following ways or supply incorrect signal

1. Sensor open circuit.
2. Short circuit to vehicle supply.
3. Short circuit to vehicle earth.
4. Sensor disconnected.
5. Stoichiometric ratio outside the correct operating band.
6. Contamination from leaded fuel.
7. Air leak into the exhaust system.
8. Wiring loom damage.
9. Sensors fitted incorrectly or cross wired.

In the event of a HO2S signal failure any of the following symptoms may be observed

1. Default to open loop fuelling on defective bank.
2. If the sensors are crossed over (LH bank to RH bank), the engine will run normally after initial start up, but performance will become progressively worse as the sensors go towards maximum rich for one bank of cylinders and maximum lean for the other. The ECM will eventually default into open loop fuelling.
3. High CO reading.
4. Excess emissions.
5. Strong hydrogen sulfide (H2S) smell until the ECM defaults to open loop fuelling.
6. MIL illuminated (NAS market only).

A number of diagnostic tests are performed by the ECM with regards to the HO2 sensors

1. HO2 sensor and system diagnostics.
2. HO2 sensor heater diagnostics.
3. HO2 sensor switching period (ageing) diagnostics.
4. Rear HO2 sensor adaption diagnostic (NAS only).
5. Catalyst monitoring diagnostic.

For further details of the heated oxygen sensors and exhaust emission control, refer to the V8 Emission Control section of this manual. Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 49)

Scheme 49

Fuel Injectors

The fuel injectors are located beneath the air inlet manifold. (Scheme 50) They utilize an electrical solenoid to lift the injector needle off its seat to allow fuel injection to take place. The fuel injectors provide excellent fuel atomization in the lower portion of the inlet manifold, the air/fuel mixture can then be drawn into the cylinders to give good combustion characteristics and therefore excellent driveability.

Scheme 50

There are eight fuel injectors one per cylinder that the ECM operates sequentially. All the injectors are fed from a common fuel rail as part of the returnless fuel system. Fuel pressure is maintained at a constant 3.5 bar (52 psi) by a regulator that is integral with the fuel pump.

All eight fuel injectors are supplied with battery voltage via fuse number 1 located in engine compartment fuse box. The ECM controls the individual earth path for each injector via its own pin at connector C0636 of the ECM multiplug. This facility allows the ECM to control the fuel injectors so that sequential fuel injection can take place.

Typical hot engine injector pulse width values

1. Idle = 2.5 ms.
2. Peak torque (3000 rev/min) = 7 ms. The ECM controls injector earth as follows: Cylinder No 1 - pin 41 of connector C0636 of the ECM multiplug. Cylinder No 2 - pin 1 of connector C0636 of the ECM multiplug. Cylinder No 3 - pin 27 of connector C0636 of the ECM multiplug. Cylinder No 4 - pin 40 of connector C0636 of the ECM multiplug. Cylinder No 5 - pin 2 of connector C0636 of the ECM multiplug. Cylinder No 6 - pin 15 of connector C0636 of the ECM multiplug. Cylinder No 7 - pin 14 of connector C0636 of the ECM multiplug. Cylinder No 8 - pin 28 of connector C0636 of the ECM multiplug.

Individual injectors can be measured for resistance using a multimeter. An acceptable injector resistance is as follows

1. 14.5 +/- 0.7 ohms at 20°C (68°F)

The fuel injectors can fail in the following ways or supply incorrect signal

1. Injector actuator open circuit.
2. Short circuit to vehicle supply.
3. Short circuit to vehicle earth.
4. Blocked injector.
5. Restricted injector.
6. Low fuel pressure.

In the event of fuel injector signal failure any of the following symptoms may be observed

1. Rough running.
2. Difficult starting.
3. Engine misfire.
4. Possible catalyst damage.
5. High emissions.
6. Adaptive fuelling disabled.
7. Adaptive idle speed control disabled.

The ECM performs three types of fuel injector diagnostic check

1. Output short circuit to earth.
2. Output short circuit to battery voltage.
3. Output open circuit.

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 51)and (Scheme 52).

Scheme 51

Scheme 52

Idle Air Control Valve (IACV)

The IACV is located on the side of the air inlet pipe on top of the engine. (Scheme 53) The IACV is used to maintain good quality idle speed under all operating conditions.

Scheme 53

When an engine is running at idle it is subject to a combination of internal and external loads that can affect idle speed. These loads include engine friction, water pump, alternator operation, and air conditioning.

The IACV acts as an air bypass valve. The ECM uses the IACV to enable the closed loop idle speed calculation to be made by the ECM. This calculation regulates the amount of air flow into the engine at idle, therefore compensating for any internal or external loads that may affect idle speed.

The IACV utilizes two coils that use opposing PWM signals to control the position of opening/closing of a rotary valve. If one of the circuits that supply the PWM signal fails, the ECM closes down the remaining signal preventing the IACV from working at its maximum/minimum setting. If this should occur, the IACV automatically resumes a default idle position. In this condition, the engine idle speed is raised and maintained at 1200 rev/min with no load placed on the engine.

The idle speed in cold start condition is held at 1200 rev/min in neutral for 20 seconds and ignition timing is retarded as a catalyst heating strategy. The cold start idle speed and the default idle position give the same engine speed 1200 rev/min, and although they are the same figure they must not be confused with each other as they are set separately by the ECM.

The input to the IACV is a 12 volt signal from fuse 2 located in the engine compartment fuse box. The output earth signal to open and close the actuator is controlled by the ECM as follows

1. IACV (open signal) - via pin 42 of connector C0636 of the ECM.
2. IACV (closed signal) - via pin 43 of connector C0636 of the ECM.

The IACV can fail the following ways or supply incorrect signal

1. Actuator faulty.
2. Rotary valve seized.
3. Wiring loom fault.
4. Connector fault.
5. Intake system air leak.
6. Blocked actuator port or hoses.
7. Restricted or crimped actuator port or hoses.

In the event of an IACV signal failure any of the following symptoms may be observed

1. Either low or high idle speed.
2. Engine stalls.
3. Difficult starting.
4. Idle speed in default condition.

There are eight IACV diagnostic checks performed by the ECM

1. Output short circuit to earth - opening coil.
2. Output short circuit to battery supply - opening coil.
3. Output open circuit - opening coil.
4. Output short circuit to earth - closing coil.
5. Output short circuit to battery voltage - closing coil.
6. Output open circuit - closing coil.
7. Blocked IACV - rev/min error low (engine speed must be 100 rev/min less than the target speed, engine load less than 2.5 and the measured air flow more than 10 kg/h less than the expected air flow for a fault condition to be flagged).
8. Blocked IACV - rev/min error high (the engine speed must be more than 180 rev/min greater than the target speed and the measured air flow more than 10 kg/h greater than the expected air flow for a fault condition to be flagged).

Should a malfunction of the component occur, the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 54)

Scheme 54

Fuel Pump Relay

The fuel pump relay is located in the engine compartment fuse box. (Scheme 55) It is a 4 pin normally open relay. Input from the ECM allows the fuel pump relay to control the electrical input to the fuel pump, regulating the fuel supply to the fuel injectors. When the ignition is switched on and the engine is cranked, the fuel pump relay is activated by the ECM, allowing the fuel system to be pressurized to 3.5 bar (52 psi). The ECM then deactivates the relay until the engine has started.

If the fuel pump runs, but the fuel pressure is out of limits, adaptive fuel faults will be stored.

Scheme 55

The input value for the relay windings is battery voltage, the input value for the switching contacts comes from fuse 10 in the engine compartment fuse box. The output control of the switching contacts is direct to the fuel pump motor, and the relay windings are controlled by pin number 18 of connector C0635 of the ECM.

At ignition ON (position II) the fuel pump relay contacts remain open until the ECM supplies an earth path for the relay windings via pin number 18 of connector C0635 of the ECM. At this point, the relay windings are energized, drawing the relay contacts closed. This allows voltage from fuse 10 in the passenger compartment fuse box to pass directly to the fuel pump.

The fuel pump relay can fail the following ways or supply incorrect signal

1. Relay drive open circuit.
2. Short circuit to vehicle earth.
3. Short circuit to vehicle supply.
4. Component failure.

In the event of a fuel pump relay failure any of the following symptoms may be observed

1. Engine stalls or will not start.
2. No fuel pressure at the fuel injectors.

The ECM performs three types of diagnostic test to confirm the fuel pump relay integrity

1. Output short circuit to earth.
2. Output short circuit to battery voltage.
3. Output open circuit.

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 56)

Scheme 56

EVAPORATIVE EMISSIONS

Refer to Emissions section for description of the evaporative emissions system components. See EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, EVAPORATIVE EMISSION CONTROL SYSTEM. .

SECONDARY AIR INJECTION (NAS ONLY)

Refer to Emissions section for description of the secondary air injection system components. See EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, SECONDARY AIR INJECTION SYSTEM. .

FUEL TANK PRESSURE SENSOR (NAS ONLY)

Refer to Fuel Delivery section for description of the fuel system components. See FUEL DELIVERY SYSTEM - V8, DESCRIPTION AND OPERATION, DESCRIPTION .

Refer to Emissions section for description of the fuel tank pressure sensor. See EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, EVAPORATIVE EMISSION CONTROL SYSTEM .

Ignition Coils

Two double ended ignition coils are located at the rear of the engine, below the inlet plenum camber mounted on a bracket. (Scheme 57) The ignition system operates on the wasted spark principle. When the ECM triggers an ignition coil to spark, current from the coil travels to one spark plug jumping the gap at the spark plug electrodes igniting the mixture in the cylinder. Current continues to travel along the earth path (via the cylinder head) to the spark plug negative electrode at the cylinder that is on the exhaust stroke. The current jumps across the spark plug electrodes and back to the coil completing the circuit. Since it has sparked simultaneously in a cylinder that is on the exhaust stroke it has not done any work, therefore it is wasted.

Scheme 57

The coils are paired in the following cylinder order

1. 1 and 6.
2. 8 and 5.
3. 4 and 7.
4. 3 and 2.

The ECM calculates the dwell timing from battery voltage, and engine speed to ensure constant secondary energy. This ensures sufficient spark energy is always available without excessive primary current flow and thus avoiding overheating or damage to the coils. Individual cylinder spark timing is calculated from the following signals

1. Engine speed.
2. Engine load.
3. Engine temperature.
4. Knock control.
5. Automatic gearbox shift control.
6. Idle speed control.

During engine warm up ignition timing should be an expected value of 12° BTDC.

TestBook/T4 can not directly carry out diagnostics on the high-tension side of the ignition system. Ignition related faults are monitored indirectly by the misfire detection system.

Input to the low tension side of the ignition coils comes from Fuse 14 located in the passenger compartment fuse box. This fuse provides battery power for two ignition coils.

It is possible to test both primary and secondary coils of the ignition coils for resistance using a multimeter as follows

1. Expected primary coil resistance: 0.5 +/- 0.05 ohms at 20°C (68°F).
2. Expected secondary coil resistance: 13.3 +/- 1.3 kohms at 20°C (68°F).

The ECM provides the earth control for each coil on separate pins as follows

1. LH Bank (cylinders 1, 3, 5, 7): Cylinder 1 - pin 6 of connector C0638 of the ECM multiplug. Cylinder 3 - pin 2 of connector C0638 of the ECM multiplug. Cylinder 5 - pin 8 of connector C0638 of the ECM multiplug. Cylinder 7 - pin 7 of connector C0638 of the ECM multiplug.
2. RH Bank (cylinders 2, 4, 6, 8): Cylinder 2 - pin 2 of connector C0638 of the ECM multiplug. Cylinder 4 - pin 7 of connector C0638 of the ECM multiplug. Cylinder 6 - pin 6 of connector C0638 of the ECM multiplug. Cylinder 8 - pin 8 of connector C0638 of the ECM multiplug.

The ignition coil can fail the following ways or supply incorrect signal

1. Coil open circuit.
2. Short circuit to vehicle supply.
3. Short circuit to vehicle earth.
4. Faulty component.

In the event of ignition coil failure any of the following symptoms may be observed

1. Engine misfire on specific cylinders.
2. Engine will not start.

Knock Sensor (KS)

The ECM uses two knock sensors located between the center two cylinders of each bank to detect pre-ignition. (Scheme 58) The knock sensors consist of piezo ceramic crystals that oscillate to create a voltage signal. During pre-ignition the frequency of crystal oscillation increases, which alters the signal output to the ECM. The ECM compares the signal to known signal profiles in its memory. If pre-ignition is detected the ECM retards ignition timing for a number of cycles. If no more pre-ignition is detected, the timing is gradually advanced to the original setting.

Scheme 58

The ignition is calibrated to run on 95 RON premium fuel, but the system will run satisfactorily on 91 RON regular fuel. If the vehicle is refuelled with a lower grade fuel, some audible detonation will initially be heard. This is non-damaging and ceases when the system adaption is completed.

Because of the nature of its operation, the knock sensors do not require any electrical input source. The KS output for LH bank (cylinders 1, 3, 5, 7) is measured via pin 49 of connector C0636 of the ECM. The KS output for RH bank (cylinders 2, 4, 6, 8) is measured via pin 36 of connector C0636 of the ECM. Both knock sensors have a screened earth to protect the integrity of the sensor signals. The KS earth for LH bank (cylinders 1, 3, 5, 7) is via pin 48 of connector C0636 of the ECM. The KS earth for RH bank (cylinders 2, 4, 6, 8) is via pin 35 of connector C0636 of the ECM.

The connector and sensor terminals are gold plated for corrosion and temperature resistance, care must be exercised while probing the connector and sensor terminals.

The KS can fail the following ways or supply incorrect signal

1. Sensor open circuit.
2. Short circuit to vehicle battery supply.
3. Short circuit to vehicle earth.
4. Faulty component.
5. Incorrectly tightened sensor.

In the event of a KS signal failure any of the following symptoms may be observed

1. KS disabled, the ECM refers to a SAFE IGNITION MAP.
2. Rough running.
3. Engine performance concern.

The ECM performs the following diagnostic checks to confirm correct knock sensor operation

1. KS signal level is less than the minimum threshold (dependent on engine speed) - the engine must be running, coolant temperature above 60°C (140°F), number of camshaft revolutions since start greater than 50 and the KS signal profile must be less than the threshold value at a given engine speed for a fault condition to be flagged.
2. KS signal is greater than the maximum threshold (dependent on engine speed) - the engine must be running, coolant temperature above 60°C (140°F), number of camshaft revolutions since start greater than 50 and the KS signal profile must be greater than the threshold value at a given engine speed for a fault condition to be flagged.
3. Error counter for verification of knock internal circuitry exceeded - the engine must be running, coolant temperature above 60°C (140°F), number of camshaft revolutions since start greater than 50 and the error counter greater than the threshold value at a given engine speed for a fault condition to be flagged.

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 59)

Scheme 59

Spark Plugs

The spark plugs are platinum tipped on both center and earth electrodes. The platinum tips give a long maintenance free life.

Cleaning or resetting the spark plug gap is not recommended as this could result in damaging the platinum tips and thereby reducing reliability.

The misfire detection system will malfunction and store erroneous codes if the incorrect spark plugs are used.

The ignition coils provide a voltage to the spark plugs via the HT leads. The cylinder head via the individual thread of each spark plug provides the earth path.

The spark plugs can fail in the following ways

1. Faulty component.
2. Connector or wiring fault.
3. Breakdown of high tension lead causing tracking to chassis earth.
4. Incorrect spark plugs fitted.

In the event of a spark plug failure, misfire on specific cylinder may be observed.

High Tension (HT) Leads

The HT leads are located on top of the engine, below the plenum chamber. (Scheme 60) Their function is to transfer the HT voltage generated by the ignition coils to the spark plugs in the engine.

Scheme 60

The input to the HT lead is HT voltage from the ignition coil pack. The HT lead then supplies this voltage to the spark plug. Output HT voltage is used by the spark plugs to ignite the air/fuel mixture in the combustion chamber.

The HT leads can fail in the following ways

1. Connector/Wiring fault.
2. Faulty component causing spark tracking to chassis earth.
3. Damage to HT leads during component removal.

In the event of a HT lead failure the following symptom may be observed

1. Misfire on specific cylinder.

All ignition system related faults are diagnosed by the misfire detection system and its fault codes.

HILL DECENT CONTROL (HDC)

Refer to Brakes for description of the hill descent control. See BRAKES, DESCRIPTION AND OPERATION, DESCRIPTION .

HIGH/LOW RATIO SWITCH

Refer to Transfer Box for description of the high/low ratio switch transfer box components. See TRANSFER CASE .

MIL/Service Engine Soon Warning Lamp

The MIL/service engine soon warning lamp is located in the instrument cluster. (Scheme 61) It illuminates to alert the driver to system malfunctions. Service engine soon warning lamp is the name for this warning lamp in NAS only, it is called MIL in all other markets.

Scheme 61

During ignition a self-test function of the lamp is carried out. The lamp will illuminate for 3 seconds then it will extinguish if no faults exist. See INSTRUMENTS, DESCRIPTION AND OPERATION, DESCRIPTION .

The MIL is supplied with battery voltage from the instrument cluster. When the ECM detects a fault, it provides an earth path to illuminate the MIL. Output to the MIL is via pin 20 of connector C0637 of the ECM.

Air Temperature Control (ATC) Request

The ATC request comes via the ATC switch located in the fascia panel. When the driver operates the switch it acts as a request from the ATC ECU to engage the ATC clutch to drive the system.

During periods of high driver demand such as hard acceleration or maximum rev/min the ATC clutch will be disabled for a short time. This is to reduce the load on the engine. See AIR CONDITIONING, DESCRIPTION AND OPERATION, DESCRIPTION .

The operation of the ATC request is via a switch being connected to earth. Voltage is supplied via pin 38 of connector C0637 of the ECM, at the point at when the switch is pressed the connection is made and the ATC clutch is engaged.

The ATC request can fail as follows

1. Open circuit.
2. Short circuit to voltage supply.
3. Short circuit to vehicle earth.
4. Wiring loom fault.

In the event of an ATC request failure, the ATC system does not work.

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 62)

Scheme 62

ATC Compressor Clutch Relay

The ATC compressor clutch relay is located in the engine compartment fuse box. (Scheme 63) It is a four pin normally open relay. The relay must be energized to drive the ATC compressor clutch.

Scheme 63

The ECM provides the earth for the relay coil to allow the relay contacts to close and the ATC clutch drive to receive battery voltage. The ECM uses a transistor as a switch to generate an open circuit in the earth path of the relay coil. When the ECM opens the earth path, the return spring in the relay will pull the contacts apart to shut down the ATC clutch drive.

Input to the ATC clutch relay switching contacts is via fuse 6 located in the engine compartment fuse box. The relay coils are supplied with battery voltage from the main relay, also located in the engine compartment fuse box. The earth path for the relay coil is via pin 29 of the ECM C0657 connector. When the relay is energized the output from the switching contacts goes directly to the ATC compressor clutch.

The ATC clutch relay can fail in the following ways

1. Relay open circuit.
2. Short circuit to vehicle supply.
3. Short circuit to vehicle earth.
4. Broken return spring.

In the event of an ATC clutch relay failure, the ATC does not work.

Should a malfunction of the component occur, the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 64)

Scheme 64

Cooling Fan Relay

The cooling fan relay is located in the engine compartment fuse box. (Scheme 65) It is a four pin normally open relay. The relay must be energized to drive the cooling fan.

Scheme 65

The cooling fan is used to cool both the condenser in which the ATC refrigerant is held and the radiator. This fan is used especially when the engine is operating at excessively high temperatures. It is also used as a part of the ECM backup strategy if the ECT fails.

The ECM provides the earth for the relay coils to allow the relay contacts to close and the cooling fan motor to receive battery voltage. The ECM uses a transistor as a switch to generate an open circuit in the earth path of the relay windings. When the ECM opens the earth path, the return spring in the relay will pull the contacts apart to shut down the cooling fan motor drive.

Input to the cooling fan relay switching contacts is via fuse 5 located in the engine compartment fuse box. The relay coils are supplied with battery voltage from the main relay, also located in the engine compartment fuse box. The earth path for the relay coils is via pin 31 of the ECM connector C0636. When the relay is energized the output from the switching contacts is directly to the cooling fan motor.

The cooling fan relay can fail in the following ways

1. Relay open circuit.
2. Short circuit to vehicle battery supply.
3. Short circuit to vehicle earth.
4. Broken return spring.

In the event of a cooling fan relay failure, the cooling fan does not work.

FUEL QUANTITY

The ECM controls engine fuel quantity by providing sequential injection to the cylinders. Sequential injection allows each injector to deliver fuel to the cylinders in the required firing order.

To achieve optimum fuel quantity under all driving conditions, the ECM provides an adaptive fuel strategy.

Conditions

Adaptive fuel strategy must be maintained under all throttle positions except

1. Cold starting.
2. Hot starting.
3. Wide open throttle.
4. Acceleration.

All of the throttle positions mentioned above are deemed to be OPEN LOOP. Open loop fuelling does not rely on information from the HO2 sensors, but the air/fuel ratio is set directly by the ECM. During cold start conditions the ECM uses ECT information to allow more fuel to be injected into the cylinders to facilitate cold starting. This strategy is maintained until the HO2 sensors are at working temperature and can pass exhaust gas information to the ECM. Because of the specific nature of the other functions e.g. hot starting, idle, wide open throttle, and acceleration they also require an OPEN LOOP strategy. For NAS vehicles with secondary air injection for cold start conditions, refer to the Emissions section. See EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, SECONDARY AIR INJECTION SYSTEM .

Adaptive fuel strategy also allows for wear in the engine and components, as well as slight differences in component signals, as no two components will give exactly the same readings.

Function

To be able to calculate the amount of fuel to be injected into each cylinder, the ECM needs to determine the amount of air mass drawn into each cylinder. To perform this calculation, the ECM processes information from the following sensors

1. Mass air flow (MAF) sensor.
2. Crank speed and position (CKP) sensor.
3. Engine coolant temperature (ECT) sensor.
4. Throttle position (TP) sensor.

During one engine revolution, 4 of the 8 cylinders draw in air. The ECM uses CKP sensor information to determine that one engine revolution has taken place, and the MAF sensor information to determine how much air has been drawn into engine. The amount of air drawn into each cylinder is therefore 1/4 of the total amount measured by the ECM via the MAF sensor.

The ECM refers the measured air mass against a fuel quantity map in its memory and then supplies an earth path to the relevant fuel injector for a period corresponding to the exact amount of fuel to be injected into the lower inlet manifold. This fuel quantity is in direct relation to the air mass drawn into each cylinder to provide the optimum ratio.

During adaptive fuelling conditions, information from the heated oxygen sensors (HO2S) is used by the ECM to correct the fuel quantity to keep the air/fuel ratio as close to the stoichiometric ideal as possible.

CLOSED LOOP FUELLING

The ECM uses a closed loop fuelling system as part of its fuelling strategy. The operation of the three-way catalytic converter relies on the ECM being able to optimize the air/fuel mixture, switching between rich and lean either side of lambda one. Closed loop fuelling is not standard for all markets, vehicles that are not fitted with HO2S do not have closed loop fuelling.

The ideal stoichiometric ratio is represented by lambda = 1. The ratio can be explained as 14.7 parts of air to every 1 part of fuel.

To achieve closed loop fuelling, the ECM interacts with the following components

1. HO2S.
2. Fuel injectors.

Closed loop fuelling is a rolling process controlled by the ECM. The ECM uses information gained from the CKP, ECT, MAF/IAT and the TP sensors, to operate under the following conditions

1. Part throttle.
2. Light engine load.
3. Cruising.
4. Idle.

When the engine is operating in the above conditions, the ECM implements the closed loop fuelling strategy. The air/fuel mixture is ignited by the High Tension (HT) spark in the combustion chambers and the resulting gas is expelled into the exhaust pipe. Upon entering the exhaust pipe the exhaust gas passes over the protruding tip of the HO2S. The HO2S measures the oxygen content of the gas compared to that of ambient air and converts it into a voltage, which is measured by the ECM.

The voltage signal read by the ECM is proportional to the oxygen content of the exhaust gas. This signal can then be compared to stored values in the ECM's memory and an adaptive strategy can be implemented.

If the HO2S informs the ECM of an excess of oxygen (lean mixture), the ECM extends the opening time of the fuel injectors via the Injector Pulse Width (IPW) signal. Once this new air/fuel ratio has been BURNT in the combustion chambers the HO2S can again inform the ECM of the exhaust gas oxygen content, this time there will be a lack of oxygen or a rich mixture. The ECM reduces the opening time of the injectors via the IPW signal using the ECM's adaptive fuel strategy. During closed loop fuelling the HO2S will constantly switch from rich to lean and back again, this indicates that the ECM and the HO2S are operating correctly.

OPEN LOOP FUELLING

Open loop fuelling does not rely on information from the HO2S, but the air/fuel ratio is set directly by the ECM, which uses information gained from the ECT, MAF/IAT, the TP sensors and also the vehicle speed sensor (VSS). The ECM uses open loop fuelling under the following conditions

1. Cold start.
2. Hot start.
3. Wide open throttle.
4. Acceleration.

The ECM uses open loop fuelling to control fuel quantity in all non adaptive strategy conditions. The ECM implements fuelling information carried in the form of specific mapped data contained within its memory.

Because there is no sensor information (e.g. HO2S), provided back to the ECM, the process is called an OPEN LOOP.

The ECM will also go into open loop fuelling if a HO2S fails.

IGNITION TIMING

The ignition timing is an important part of the ECM adaptive strategy. Ignition is controlled by a direct ignition system using two four-ended coils operating on the wasted spark principle.

When the ECM triggers an ignition coil to spark, current from the coil travels to one spark plug, then jumps the gap at the spark plug electrodes, igniting the mixture in the cylinder in the process. Current continues to travel along the earth path (via the cylinder head) to the spark plug negative electrode at the cylinder that is on the exhaust stroke. The current jumps across the spark plug electrodes and back to the coil completing the circuit. Since it has simultaneously sparked in a cylinder that is on the exhaust stroke, it has not provided an ignition source there and is consequently termed WASTED.

The ECM calculates ignition timing using input from the following

1. CKP Sensor
2. Knock Sensors
3. MAF Sensor
4. TP Sensor (idle only)
5. ECT Sensor

At engine start up, the ECM sets ignition timing dependent on ECT information and starting rev/min from the CKP. As the running characteristics of the engine change, the ignition timing changes. The ECM compares the CKP signal to stored values in its memory, and if necessary advances or retards the spark via the ignition coils.

Ignition timing is used by the ECM for knock control.

KNOCK CONTROL

The ECM uses active knock control to prevent possible engine damage due to pre-ignition. This is achieved by converting engine block noise into a suitable electrical signal that can be processed by the ECM. A major contributing factor to engine KNOCK is fuel quality, the ECM can function satisfactorily on 91 RON fuel as well as the 95 RON fuel that it is calibrated for.

The ECM knock control system operates as follows

1. Hot running engine.
2. 91 or 95 RON fuel.

The ECM knock control uses two sensors located one between the center two cylinders of each bank. The knock sensors consist of piezo ceramic crystals that oscillate to create a voltage signal. During pre-ignition, the frequency of crystal oscillation increases which alters the signal output to the ECM.

If the knock sensors detect pre-ignition in any of the cylinders, the ECM retards the ignition timing by 3° for that particular cylinder. If this action stops the engine knock, the ignition timing is restored to its previous figure in increments of 0.75°. If this action does not stop engine knock then the ECM retards the ignition timing a further 3° up to a maximum of -15° and then restores it by 0.75° and so on until the engine knock is eliminated.

The ECM also counteracts engine knock at high intake air temperatures by retarding the ignition as above. The ECM uses the IAT signal to determine air temperature.

IDLE SPEED CONTROL

The ECM regulates the engine speed at idling. The ECM uses the idle air control valve (IACV) to compensate for the idle speed drop that occurs when the engine is placed under greater load than usual. When the throttle is in the rest position i.e. it has not been pressed, the majority of intake air that the engine consumes comes from the idle air control valve.

IACV Control Idle Speed

Conditions in which the ECM operates the IACV control idle speed is as follows

1. If any automatic transmission gears other than P or N are selected.
2. If air conditioning is switched on.
3. If cooling fans are switched on.
4. Any electrical loads activated by the driver.

The idle air control valve utilizes two coils that use opposing pulse width modulated (PWM) signals to control the position of a rotary valve. If one of the circuits that supplies the PWM signal fails, the ECM closes down the remaining signal preventing the idle air control valve from working at its maximum/minimum setting. If this should occur, the idle air control valve assumes a default idle position at which the engine idle speed is raised to 1200 rev/min with no load placed on the engine.

EVAPORATIVE EMISSION CONTROL

Due to increasing legislation, all new vehicles must be able to limit evaporative emissions (fuel vapor) from the fuel tank.

The ECM controls the emission control system using the following components

1. EVAP canister.
2. Purge valve.
3. Canister vent solenoid (CVS) valve - (NAS vehicles with vacuum type EVAP system leak detection capability only).
4. Fuel tank pressure sensor - (NAS vehicles with vacuum type EVAP system leak detection capability only).
5. Fuel leak detection pump - (NAS vehicles with positive pressure type EVAP system leak detection capability only).
6. Interconnecting pipe work.

Refer to Emissions section for operating conditions of evaporative emission systems. See EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, EVAPORATIVE EMISSION CONTROL OPERATION .

ON-BOARD DIAGNOSTICS (OBD) - NORTH AMERICAN SPECIFICATION (NAS) VEHICLES ONLY

The ECM monitors performance of the engine for misfires, catalyst efficiency, exhaust leaks and evaporative control loss. If a fault occurs, the ECM stores the relevant fault code and warns the driver of component failure by illuminating the Malfunction Indicator Light in the instrument pack.

On vehicles fitted with automatic gearbox, the ECM combines with the Electronic Automatic Transmission (EAT) ECU to provide the OBD strategy.

If the OBD function of the ECM flags a fault during its operation, it falls into one of the following categories

1. Min = minimum value of the signal exceeded.
2. Max = maximum value of the signal exceeded.
3. Signal = signal not present.
4. Plaus = an implausible condition has been diagnosed.

All of the ECM's internal diagnostic fault paths are monitored by the OBD system. Specific faults have their own numeric code relating to certain sensors or actuators etc. These specific faults fall into two types, error codes (E xxx) or cycle codes (Z xxx). E codes represent instantaneous faults and Z codes relate to codes generated after completion of a drive cycle.

If an emission relevant fault occurs on a drive cycle, the ECM stores a temporary fault code, if the fault does not occur on subsequent drive cycles the fault code stays as a temporary fault code. If the fault recurs on subsequent drive cycles the ECM stores the fault code as a permanent code, and depending on which component has failed the ECM will illuminate the MIL.

IMMOBILIZATION SYSTEM

The ECM and the body control unit (BCU) security system comprise the immobilization system.

The ECM and the BCU combine to prevent the engine from running unless the appropriate security criteria are met.

The ECM and the BCU are a matched pair, if either one is replaced for any reason, the system will not operate unless the replaced unit is correctly matched to its original specification. Textbook/T4 must be used to reconfigure the immobilization system.

The ECM operates immobilization in three states

1. New
2. Secure
3. No Code

With the ECM operating in the NEW state, Textbook/T4 is required to instruct the ECM to learn the new BCU code. If the ECM is in delivery state (i.e. direct from the supplier), it will not run the vehicle and will store a new ECM fault code when it is fitted. This code must be cleared after instructing the ECM to learn the BCU code using Textbook/T4.

When the ECM is in the SECURE state, no further action is required as the ECM has successfully learned the BCU code. A SECURE ECM can not be configured to a NO CODE state.

If the vehicle is fitted with an ECM with a valid code, the engine will start and the MIL will go out.

However, if the ECM has an invalid BCU security code the engine will crank, start, and then immediately stall. The status of the security system can only be interrogated using Textbook/T4.

Textbook/T4 is able to retrieve the following immobilization fault codes. (Scheme 66)

Scheme 66

MISFIRE DETECTION

Due to increasing legislation, all new vehicles must be able to detect two specific levels of misfire.

The ECM is able to carry out misfire detection as part of the OBD system using the following component parts

1. Flywheel reluctor adaptation.
2. Calculation of engine roughness.
3. Detection of excess emissions misfire.
4. Detection of catalyst damaging misfire.

Note. The flywheel/reluctor ring adaptions must be reset if the CKP sensor or the flywheel are changed.

The flywheel/reluctor ring is divided into four segments 90° wide. The ECM misfire detection system uses information generated by the CKP to determine crankshaft speed and position. If a misfire occurs, there will be an instantaneous slight decrease in engine speed. The ECM misfire detection system is able to compare the length of time each 90° segment takes and is therefore able to pinpoint the source of the misfire.

For the ECM misfire detection system to be calibrated for the tolerances of the reluctor tooth positions, the flywheel/reluctor ring must be ADAPTED as follows

1. 1800 - 3000 rev/min = speed range 1.
2. 3000 - 3800 rev/min = speed range 2.
3. 3800 - 4600 rev/min = speed range 3.
4. 4600 - 5400 rev/min = speed range 4.

The ECM carries out flywheel/reluctor ring adaptions across all the above speed ranges and can be monitored by Textbook/T4. The test should be carried out as follows

1. Engine at normal operating temperature.
2. Select second gear (for both automatic and manual transmission vehicles).
3. Accelerate until engine rev limiter is operational.
4. Release throttle smoothly to allow engine to decelerate throughout the speed ranges.
5. Repeat process as necessary until all adaptations are complete.

Textbook/T4 is able to retrieve the following misfire detection fault codes. (Scheme 67)

Scheme 67

Textbook/T4 is able to retrieve the following Catalyst damage fault codes. (Scheme 68)

Scheme 68

VEHICLE SPEED SIGNAL (VSS)

The VSS is used, by the ECM, to control idle speed and overrun cut off. The ECM receives the signal through a hard wired connection direct from the SLABS ECU.

For vehicles fitted with an automatic gearbox, two vehicle speed signals are received by the ECM. The second signal is derived from the main gearbox output shaft speed, and is sent to the ECM by the Electronic Automatic Transmission (EAT) ECU though the Controller Area Network (CAN). The ECM compares the vehicle speed signal generated by the SLABS ECU with that supplied via the CAN.

The ECM also receives transfer box information. This allows the ECM to take in to account the vehicle being driven using low range gearing and compensate as necessary.

On vehicles with manual transmission, the SLABS signal is checked against a threshold value stored in ECM memory. If other engine parameters indicate the engine is at high load and the VSS is below the threshold, a fault condition is registered in the diagnostic memory.

The vehicle speed signal generated by the SLABS ECU is in the form of a pulse width modulated signal (PWM). Pulses are generated at 8000 per mile, and the frequency of the signal changes in accordance with road speed. At zero road speed the ECU outputs a reference signal at a frequency of 2 Hz for diagnostic purposes.

Function The input signal for the SLABS ECU is measured via pin 22 of connector C0637 of the ECM. The SLABS ECU generates a PWM signal switching between 0 and 12 volts at a frequency of 8000 pulses per mile. For vehicles with automatic gearbox the input signal for the EAT ECU is measured via pins 36 and 37 of connector C0637 of the ECM. These pin numbers provide a bi-directional communications link using the CAN data bus.

In the case of a VSS failure on vehicles with automatic gearboxes, the ECM applies default values derived from the EAT ECU. There are no default values for manual gearbox vehicles.

The VSS can fail in the following ways

1. Wiring short circuit to vehicle supply.
2. Wiring short circuit to vehicle earth.
3. Wiring open circuit.

In the event of a VSS failure, any of the following symptoms may be observed

1. MIL illuminated after 2 driving cycles (NAS only).
2. Vehicle speed limiting disabled (manual transmission vehicles only).
3. SLABS/HDC warning lamp on and audible warning.

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 69)

Scheme 69

ROUGH ROAD SIGNAL

When the vehicle travels across rough terrain, or on rough roads instability becomes evident in the drive train. The ECM could interpret these vibrations as a FALSE MISFIRE. To counteract this FALSE MISFIRE the SLABS ECU generates a rough road signal, sends it to the ECM so that the ECM can suspend misfire detection for as long as the vehicle is travelling on the ROUGH ROAD.

Input for the rough road signal is measured via pin 34 of connector C0637 of the ECM. The SLABS ECU generates a PWM signal that varies in accordance with changing road conditions. The rough road PWM signal operates at a frequency of 2.33 Hz +/- 10%. The significance of changes in the PWM signal are shown in the following table. See ROUGH ROAD SIGNAL PWM SIGNAL .

ROUGH ROAD SIGNAL PWM SIGNAL

The rough road signal can fail in the following ways

1. Harness or connector damage.
2. SLABS failure - wheel speed sensor.

A rough road signal failure may be evident from the following

1. HDC/ABS warning light on.

Should a malfunction of the rough road signal occur, the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 70)

Scheme 70

HILL DESCENT CONTROL (HDC) SIGNAL

The ECM transmits throttle angle, engine torque, engine identification (Td5 or V8), and transmission type (automatic or manual) data to the SLABS ECU to support the Hill Descent Control system. The information is transmitted via a 0-12V Pulse Width Modulated (PWM) signal at a frequency of 179.27 Hz.

The HDC signal output from the ECM is via pin 29 of connector C0636. The ECM generates a PWM signal that varies in pulse width in accordance with changing throttle angle or engine torque. The throttle angle data is transmitted on pulses 1, 3, 5 and 37. The engine torque data is transmitted on pulses 2,4,6 and 38. The engine and transmission information is transmitted on pulse 39. A synchronizing pulse is transmitted after every 39th pulse.

The HDC signal can fail in the following ways

1. Harness or connector damage.

A HDC signal failure may be evident from the following

1. HDC/ABS warning light on.
2. HDC inoperative.
3. Audible warning.

Should a malfunction of the HDC signal occur, the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 71)

Scheme 71

LOW FUEL LEVEL SIGNAL

When the fuel level in the fuel tank becomes low enough to illuminate the low fuel level warning lamp in the instrument cluster, the instrument cluster generates a low fuel level signal. If the low fuel level signal is present during the ECM misfire detection function the ECM can use it to check for a FALSE MISFIRE.

The fuel sender generates the low fuel level signal when the fuel sender resistance is greater than 158 +/- 8 ohms.

The illumination of the low fuel level warning lamp in the instrument cluster triggers the low fuel level signal to be sent to the ECM. This signal is processed via pin 8 of connector C0637 of the ECM.

Should a misfire occur while the fuel level is low, the following fault code may be evident and can be retrieved by TestBook/T4. (Scheme 72)

Scheme 72

COOLANT TEMPERATURE GAUGE SIGNAL

The ECM controls the temperature gauge in the instrument cluster. The ECM sends a coolant temperature signal to the temperature gauge in the instrument cluster in the form of a PWM square wave signal.

The frequency of the signal determines the level of the temperature gauge.

Conditions The ECM operates the PWM signal under the following parameters

1. 40°C (-40°F) = a pulse width of 768 micro seconds.
2. 140°C (284°F) = a pulse width of 4848 micro seconds.

Function The coolant temperature signal is an output from the ECM to the instrument cluster. The coolant temperature signal is generated via pin 44 of connector C0636 of the ECM.

The coolant temperature signal can fail in the following ways

1. Wiring short circuit to vehicle supply.
2. Wiring short circuit to vehicle earth.
3. Wiring open circuit.

In the event of a coolant temperature signal failure any of the following symptoms may be observed

1. Coolant temperature gauge will read cold at all times.
2. Coolant temperature warning lamp remains on at all times.

CONTROLLER AREA NETWORK (CAN) SYSTEM

The controller area network (CAN) system is a high speed serial interface between the ECM and the Electronic Automatic Transmission (EAT) ECU. The CAN system uses a 'data bus' to transmit information messages between the ECM and the EAT ECU. Because there are only two components in this CAN system, one will transmit information messages and the other will receive information messages, and vice-versa.

Conditions The CAN system is used by the EAT ECU and the ECM for transmission of the following information

1. Gearshift torque control information.
2. EAT OBD information.
3. MIL request.
4. Vehicle speed signal.
5. Engine temperature.
6. Engine torque and speed.
7. Gear selected.
8. Gear change information.
9. Altitude adaptation factor.
10. Air intake temperature.
11. Throttle angle/pedal position.

The CAN system uses a twisted pair of wires to form the DATA BUS to minimize electrical interference. This method of serial interface is very reliable and very fast. The information messages are structured so that each of the receivers (ECM or EAT ECU) is able to interpret and react to the messages sent.

The CAN DATA BUS is directly connected between pin 36 of connector C0637 of the ECM and pin 16 of connector C0193 at the EAT ECU, and pin 37 of connector C0637 of the ECM and pin 44 of connector C0193 at the EAT ECU.

The CAN system can fail in the following ways

1. CAN data bus wiring open circuit.
2. CAN data bus wiring short circuit.

In the event of a CAN data bus failure any of the following symptoms may be observed

1. MIL illuminated after 2 drive cycles (NAS only).
2. EAT defaults to 3rd gear only.
3. Harsh gearshifts.
4. SPORT and MANUAL lights flash alternately.

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook/T4. (Scheme 73)

Scheme 73

DRIVE CYCLES

The following are the Textbook/T4 drive cycles

Drive Cycle A

1. Switch on the ignition for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Connect Textbook/T4 and check for fault codes.

Drive Cycle B

1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5. Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6. Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7. Allow engine to idle for 2 minutes.
8. Connect Textbook/T4 and with the engine still running, check for fault codes.

Drive Cycle C

1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5. Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6. Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7. Cruise at 60 mph (100 km/h) for 8 minutes.
8. Cruise at 50 mph (80 km/h) for 3 minutes.
9. Allow engine to idle for 3 minutes.
10. Connect Textbook/T4 and with the engine still running, check for fault codes.

Note. The following areas have an associated readiness test which must be flagged as complete, before a problem resolution can be verified: Catalytic converter fault. Evaporative loss system fault. HO2 sensor fault. HO2 sensor heater fault. When carrying out a drive cycle C to determine a fault in any of the above areas, select the readiness test icon to verify that the test has been flagged as complete.

Drive Cycle D

1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 35°C (95°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5. Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6. Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7. Cruise at 60 mph (100 km/h) for 5 minutes.
8. Cruise at 50 mph (80 km/h) for 5 minutes.
9. Cruise at 35 mph (60 km/h) for 5 minutes.
10. Allow engine to idle for 2 minutes.
11. Connect Textbook/T4 and check for fault codes.

Drive Cycle E

1. Ensure fuel tank is at least a quarter full.
2. Carry out Drive Cycle A.
3. Switch off ignition.
4. Leave vehicle undisturbed for 20 minutes.
5. Switch on ignition.
6. Connect Textbook/T4 and check for fault codes.

For cruise control component locations (Scheme 74)

Scheme 74

BLOCK DIAGRAM

For cruise control block diagram (Scheme 75)

Scheme 75

All markets have a common cruise control system. The cruise control system, when activated, regulates vehicle speed. The system consists of an electrical sub-system and a mechanical sub-system.

The electrical sub-system consists of the following components

1. Cruise Control Master Switch (ON/OFF switch).
2. SET+ switch.
3. RES switch.
4. Cruise control ECU.
5. Vacuum pump assembly.
6. Brake pedal switch.
7. Clutch pedal switch (manual gearbox only).
8. SLABS ECU (speed signal).
9. BCU (brake pedal switch and automatic gearbox gear selector lever position signal).

The mechanical sub-system consists of the following components

1. Pneumatic actuator.
2. Vacuum pump.

The cruise control ECU controls the cruise control system. It is located on the right hand A post.

The system has diagnostic capabilities through Textbook/T4.

CRUISE CONTROL MASTER SWITCH

The cruise control master switch switches the system on and off. When the cruise control master switch is on, an LED within the switch illuminates. If the cruise control master switch is off, cruise control will not operate. The switch provides a 12 Volt feed to the cruise control ECU.

The cruise control master switch is located on the instrument panel near the steering column. (Scheme 76)

Scheme 76

The input from the cruise control master switch to the cruise control ECU is either a 12 Volts ignition feed or an open circuit. 12 Volts indicates that the cruise control master switch is on and the system can be activated. An open circuit indicates that the cruise control master switch is off and cruise control cannot be activated.

Textbook/T4 will not communicate with the cruise control ECU if the cruise control master switch is off.

SLABS ECU

The SLABS ECU provides the road speed signal to the cruise control ECU. This is the same speed signal provided to the ECM. Cruise control will only operate between 28-125 mph (45-200 km/h). Cruise control will not operate if a road speed signal is not present. For SLABS ECU location (Scheme 77)

Scheme 77

The input from the SLABS ECU to the cruise control ECU is a square wave oscillating between 0-12 Volts at a frequency of 8,000 pulses per mile (1.6 km). (Scheme 78) For ECU operating parameters, see ECU OPERATING PARAMETERS table.

Scheme 78

ECU OPERATING PARAMETERS (1)

CRUISE CONTROL ECU

The cruise control ECU controls the cruise control system. Cruise control ECU is located next to brake pedal. (Scheme 79)

Most functions of the cruise control ECU are described under other components.

Scheme 79

The diagnostic line for the cruise control system is between cruise control ECU and diagnostic socket. For Cruise Control ECU operating parameters, see CRUISE CONTROL ECU OPERATING PARAMETERS table.

The cruise control ECU does not generate fault codes, however the following system information is available via TestBook/T4

1. Last switch off reason, which was due to unacceptable speed input.
2. Speed signal detected.
3. Below minimum speed threshold.
4. Current vehicle speed.
5. Recorded SET road speed.

CRUISE CONTROL ECU OPERATING PARAMETERS (1)

SET+/RES SWITCHES

The cruise control system uses two steering wheel switches labelled SET+ and RES. (Scheme 80)

Scheme 80

The SET+ switch performs the set speed, tap up and accelerator functions. The RES switch performs the resume and suspend functions.

With the cruise control master switch on and the vehicle in the cruise control operating speed range, one press of the SET+ switch stores a speed value in the cruise control ECU. If the switch is pressed and held while the vehicle is under cruise control operation, speed increases until the switch is released. At this point the cruise control ECU stores the new speed value. If the switch is tapped (held down for less than 0.5 second) the cruise control ECU increases vehicle speed by 1 mph (1.5 km/h).

If the RES switch is pressed while the systems is inactive (no stored values) the system will not respond. If there is a stored value in the cruise control ECU memory and the switch is pressed, the cruise control system operates and holds the vehicle at the stored road speed. If the cruise control system is active and the RES switch is depressed, the cruise control ECU deactivates cruise operation but maintains the current set speed value.

The input from the SET+ switch to the cruise control ECU is either 12 Volts or an open circuit. See SET+/RES SWITCHES CRUISE CONTROL ECU OPERATING PARAMETERS table.

The input from the RES switch to the cruise control ECU is either 12 Volts or an open circuit. See SET+/RES SWITCHES CRUISE CONTROL ECU OPERATING PARAMETERS table.

The following diagnostic information is available through Textbook/T4

1. The state of operator switch SET+.
2. The state of operator switch RES.

SET+/RES SWITCHES CRUISE CONTROL ECU OPERATING PARAMETERS (1)

BRAKE PEDAL SWITCH

The cruise control ECU has two inputs from the brake pedal switch that determine the position of the brake pedal. (Scheme 81) One input comes through the BCU and is low when the brake pedal is not pressed. The second input comes directly from the brake pedal switch. This input is high when the brake pedal is not pressed. On vehicles with a manual gearbox, the input from the clutch pedal switch to the cruise control ECU is connected in series with the direct signal from the brake pedal switch.

If the cruise control ECU receives a changed signal from either source, it deactivates cruise control, removing power to the vacuum pump and activating the vacuum control valve releasing all vacuum in the system.

The brake pedal switch also provides the signal to illuminate the brake lamps and the brake input to the SLABS ECU.

Scheme 81

With the brake pedal and the clutch pedal in the rest position, the cruise control ECU receives 12 Volts. See BRAKE PEDAL & CLUTCH PEDAL SWITCHES CRUISE CONTROL ECU OPERATING PARAMETERS table.

With the brake pedal pressed, the cruise control ECU receives 0 Volts and a low voltage logic signal from the BCU.

Note. If the clutch pedal is pressed, 0 Volts are present at the cruise control ECU irrespective of brake pedal position.

BRAKE PEDAL & CLUTCH PEDAL SWITCHES CRUISE CONTROL ECU OPERATING PARAMETERS (1)

CLUTCH PEDAL SWITCH

The clutch pedal switch is a single pole normally closed switch. (Scheme 81) It is part of the 12 Volt brake pedal switch circuit to the cruise control ECU. When the clutch pedal is pressed, the cruise control ECU deactivates the cruise control system and releases system vacuum. The last set speed is retained in the cruise control ECU.

The cruise control ECU receives a 12 Volt signal through the normally closed contacts of the brake pedal switch and the normally closed clutch pedal switch.

BODY CONTROL UNIT

On manual gearbox vehicles, the BCU provides cruise control lockout or suspend function as described under brake pedal switch.

On vehicles with automatic gearbox, the BCU monitors the status of the brake pedal switch as well as the status of the automatic gearbox gear selector lever. The BCU monitors the gear selector lever to determine which gearbox position the driver has selected. If the BCU detects that the driver has selected park, reverse or neutral, it sends a signal to the cruise control ECU which inhibits cruise operation or deactivates cruise control if it is activated. For SLABS ECU location (Scheme 77)

If the BCU receives a brake pedal switch signal or an automatic gearbox gear selector lever position signal, the BCU sends a HIGH signal to the cruise control ECU. The cruise control ECU cancels or inhibits cruise control functions.

VACUUM PUMP ASSEMBLY

The vacuum pump assembly contains three components

1. The vacuum pump.
2. The vacuum control valve.
3. The vacuum dump valve.

The vacuum pump provides the vacuum for the system while the two valves work in conjunction to allow the pump to increase the vacuum to the pneumatic actuator (increase vehicle speed) or release vacuum from the pneumatic actuator (decrease vehicle speed). (Scheme 82) On vehicles from 2003 model year, the cruise control vacuum pump and pneumatic actuator assembly is fitted with a heat shield to protect the components from heat from the exhaust manifold.

Scheme 82

The vacuum control valve opens to allow the vacuum pump to increase the vacuum in the pneumatic actuator to increase vehicle speed. When the vehicle reaches the set speed, the vacuum pump control valve closes to hold vacuum in the pneumatic actuator and the vacuum pump is turned off by the cruise control ECU.

The vacuum dump valve is normally open. When cruise control is active, the cruise control ECU provides voltage to close the vacuum dump valve. If power is lost, (e.g. when the brakes or clutch are applied or cruise control is turned off at the cruise control master switch) the vacuum dump valve will immediately open and cruise control will be deactivated.

The cruise control ECU provides power for all three components within the vacuum pump assembly. The cruise control ECU provides earth control circuits for the vacuum pump and the vacuum control valve. The vacuum dump valve is permanently grounded.

The cruise control ECU provides both power and earth to the components within the vacuum pump assembly. Current draw at the vacuum pump assembly varies depending on components operating. See VACUUM PUMP CURRENT DRAW table.

VACUUM PUMP CURRENT DRAW

When cruise is requested, the cruise control ECU provides voltage to the vacuum pump assembly and provides a pulsed earth signal. The pulse period is dependent on the difference between the vehicle set speed and the actual road speed. Removing the earth path switches off the pump.

Several fault codes can be generated, as follows

1. Output Power LOW When HIGH Is Expected Flagged when Pin C0239-11 is shorted to earth. This could be due to an external fault or an internal ECU fault and will be set if pin C0239-11 is LOW for longer than 240 milliseconds, while in cruise mode.
2. Output Power HIGH When LOW Is Expected Flagged when Pin C0239-11 is shorted to battery voltage. This could be due to an external fault or internal ECU fault and will be set if pin C0239-11 is HIGH for longer than 250 milliseconds while not in cruise mode.
3. Output Pump LOW, When HIGH Is Expected Flagged when Pin C0239-7 is shorted to earth. This could be due to an external fault or an internal ECU fault. This fault will be set if pin C0239-11 is HIGH for longer than 7.5 milliseconds while pin C0239-7 is LOW for longer than 2.5 milliseconds while decelerating under control of cruise.
4. Output Pump HIGH, When LOW Is Expected Flagged when Pin C0239-7 is shorted to battery voltage. This could be due to an external fault or an internal ECU fault. This fault will be set if pin C0239-7 is LOW for longer than 7.5 milliseconds of the last 8 pulses when the pump is switched on while accelerating under the control of cruise.
5. Output Valve LOW, When HIGH Is Expected Flagged when Pin C0239-7 is shorted to battery voltage. This could be due to an external fault or an internal ECU fault and will be set if pin C0239-17 is LOW for longer than 2.5 milliseconds while pin C0239-7 is HIGH for longer than 2.5 milliseconds and pin C0239-11 is also HIGH for longer than 7.5 milliseconds, while decelerating under control of the cruise control ECU.
6. Output Valve HIGH, When LOW Is Expected Flagged when Pin C0239-17 is shorted to battery voltage. This could be an external fault or an internal ECU fault. The fault will be set if pin C0239-17 remains HIGH for longer than 35 milliseconds after the vacuum control valve is switched on, while accelerating under control of the cruise control ECU.

Textbook/T4 can be used to determine the fault codes present as well as the general status of the system.

PNEUMATIC ACTUATOR

The cruise control ECU controls the position of the throttle disc by regulating the amount of vacuum applied by the vacuum pump to the pneumatic actuator. The pneumatic actuator is an air tight bellow coupled to the pneumatic pump via a vacuum pipe. (Scheme 82) The pump evacuates the air inside the bellow and pipe, which collapses the bellow. This pulls on a cable, which moves the throttle disc to the desired position. On vehicles from 2003 model year, the cruise control vacuum pump and pneumatic actuator assembly is fitted with a heat shield to protect the components from heat from the exhaust manifold.

CRUISE CONTROL ACTIVATION

Cruise control is a passive system. The driver must activate it. Switching on the cruise control master switch located on the instrument panel activates cruise control. An LED in the switch illuminates, indicating cruise control is available. The driver must accelerate the vehicle to the desired speed using the accelerator pedal. When the desired speed is reached, pressing the SET+ switch activates cruise control.

Cruise control will only activate if the following conditions are met

1. Vehicle speed is between 28-125 mph (45-200 km/h).
2. The brake pedal is not pressed.
3. The clutch pedal is not pressed (manual gearbox only).
4. The gearbox is not in park, reverse or neutral (automatic gearbox only).

The cruise control ECU receives the set signal and determines the vehicle speed provided by the SLABS ECU. The cruise control ECU activates the vacuum pump assembly to move the pneumatic actuator and the linkage to the throttle disc to maintain set road speed. It does this by controlling the vacuum to the pneumatic actuator.

CRUISE CONTROL CANCELLATION

Cancelling cruise control enables the driver to regain control of the vehicle speed by using the accelerator pedal.

Cruise control is cancelled if any of the following conditions occur

1. The brake pedal is pressed.
2. The RES switch button is pressed.
3. The clutch pedal is pressed (manual gearbox only).
4. The cruise control master switch is turned off.
5. The gearbox is placed in park, neutral, or reverse (automatic gearbox only).

The cruise control ECU cancels cruise control operation by opening a vacuum control valve in the vacuum pump assembly. This releases the throttle linkage from the control of the pneumatic actuator and returns it to the control of the accelerator pedal.

The set speed will be stored in the cruise control ECU unless

1. The cruise control master switch is turned off.
2. The ignition switch is turned off.

If cruise control is deactivated using either of the above methods, the set speed will be erased from the memory of the cruise control ECU.

CRUISE CONTROL RESUME

Cruise control can be resumed at the previously set speed, provided the set speed has not been erased from the cruise control ECU memory as described above.

To resume cruise control operation to the previously set speed, depress the RES switch once when the following conditions are met

1. A set speed is stored in the cruise control ECU.
2. Vehicle speed is between 28-125 mph (45-200 km/h).
3. The brake pedal is not pressed.
4. The clutch pedal is not pressed (manual gearbox only).
5. The gearbox is not in park, reverse or neutral (automatic gearbox only).

The cruise control ECU activates the vacuum pump assembly to move the pneumatic actuator. This moves the throttle to the set speed by adjusting the position of the throttle disc.

ACCELERATING WHILE CRUISE CONTROL IS ACTIVE

There are three ways of increasing vehicle speed when cruise control is active

1. Temporarily increase vehicle speed (e.g. when overtaking another vehicle).
2. Increase vehicle set speed in 1 mph (1.5 km/h) increments.
3. Increase vehicle set speed.

To temporarily increase vehicle speed press the accelerator pedal until the desired speed is reached. When the accelerator pedal is released, the vehicle coasts back to the set speed. When it reaches the set speed, cruise control operation continues.

To increase the vehicle set speed in 1 mph (1.5 km/h) increments, tap the SET+ switch. Each tap on the switch increases vehicle speed.

To increase the vehicle set speed, press and hold the SET+ switch until the desired set speed is reached.

The vehicle set speed will increase if the following conditions are met

1. The vehicle is under cruise control operation.
2. Vehicle speed is between 28-125 mph (45-200 km/h).
3. The brake pedal is not pressed.
4. The clutch pedal is not pressed (manual gearbox only).
5. The gearbox is not in park, reverse or neutral (automatic gearbox only).

The vehicle responds as follows

1. If the driver accelerates using the accelerator pedal, vehicle speed increases overriding pneumatic actuator position. When the driver releases the accelerator pedal, the vehicle returns to the set speed.
2. If the SET+ switch is tapped, the driver increases the stored speed and vehicle speed by 1 mph (1.5 km/h) per tap on the switch.
3. If the driver presses and holds the SET+ switch, the vehicle speed increases until the SET+ switch is released. This becomes the new set speed for the cruise control ECU.

SWITCHING OFF CRUISE CONTROL

Switching off cruise control allows the driver to regain control of vehicle speed. It erases the set road speed from the cruise control ECU memory.

To switch off cruise control, press the cruise control master switch to the off position.

When the cruise control master switch is turned off, the cruise control ECU switches off power to the vacuum pump assembly. The vacuum dump valve opens releasing the vacuum in the pneumatic actuator, returning the throttle disc to driver control via the accelerator pedal.

See also:
• TRANSFER CASE
• ROUGH ROAD SIGNAL PWM SIGNAL