Electronic Engine Controls (Without Supercharger): Other Jaguar XKR II

IGNITION MODES

The vehicle has a possible 4 ignition modes. The modes and systems that are active in each mode are detailed in the following table.

Scheme 68

Note. A = Hardwired connection

Scheme 69

Note. A = Hardwired connection

Scheme 70

Note. D = High speed controller area network (CAN) bus; N=Medium speed controller area network (CAN) bus; O = LIN (local interconnect network) bus

The vehicle has a possible 4 ignition modes. The modes and systems that are active in each mode are detailed in the following table.

Engine Control Module (ECM)

The ECM is located in the plenum area on the passenger side of the engine compartment attached to the bulkhead.

The ECM has the following inputs

1. RCM
2. Park/neutral switch
3. Ignition coil feedback x2
4. Fuel rail temperature
5. Mass air flow
6. Engine speed
7. Camshaft position x2
8. Driver demand
9. Brake pedal position switch
10. Speed control switches
11. Generator load
12. Oxygen sensors pre catalyst x2
13. Oxygen sensors post catalyst x2
14. Throttle position
15. Cooling fan speed
16. Ignition switch position
17. Knock sensors x2
18. MAP
19. Coolant temperature
20. Engine oil temperature

The ECM outputs to the following

1. Throttle Actuator
2. Brake vacuum pump relay
3. Ignition coils (x8)
4. Oxygen sensor heaters (4)
5. Fuel injectors (8)
6. Purge Valve
7. Engine Cooling Fan
8. Fuel pump relay
9. Starter Relay
10. EMS Main Relay
11. Viscous Fan Control
12. Generator Control
13. Diagnostic Monitoring of Tank Leakage (DMTL) (NAS Only)
14. E box fan

Scheme 71

The crankshaft position sensor is mounted at the rear underside of the engine near the transmission bell housing. Connection between the sensor and the harness is via a link harness and a two-way connector. Both wires go directly to the ECM. The sensor produces the signal which enables the ECM to determine the angle of the crankshaft, and the engine RPM. From this, the point of ignition, fuel injection, etc. is calculated. If the signal wires are reversed a 3 degrees advance in timing will occur, as the electronics within the ECM uses the falling edge of the signal waveform as its reference / timing point for each tooth.

The reluctor is pressed into the flywheel and has a "tooth" pattern based on 36 teeth at 10° intervals and approximately 5° wide: one of the teeth is removed to provide a hardware reference mark which is 30 degrees BTDC (before top dead center) No.1 cylinder. Because of the crankshaft sensor's orientation, the target wheel uses windows stamped into the face, rather than actual teeth.

The sensor operates by generating an output voltage caused by the change in magnetic field that occurs as the windows pass in front of the sensor. The output voltage varies with the speed of the windows passing the sensor, the higher the engine speed, the higher the output voltage. Note that the output is also dependent on the air gap between the sensor and the teeth (the larger the gap, the weaker the signal, the lower the output voltage). The ECM transmits the engine speed to other vehicle control modules on CAN.

Scheme 72

Two sensors are located at the rear of the engine, in the cylinder head (one per bank), above the rear cylinders. The sensors are Variable Reluctor Sensor (VRS) type, producing four pulses for every two engine revolutions. The sensing element is positioned between 0 and 2mm from the side of the cam gear wheel.

The camshaft timing wheel is a sintered component which has four teeth on it to enable the EMS to detect cylinder identification. The signal is used for

1. Cylinder recognition
2. Enabling sequential fuel injection
3. Knock control
4. Cylinder identification for diagnostic purposes.

Failure symptoms include

1. Ignition timing reverting to the base mapping, with no cylinder correction.
2. Active knock control is disabled, along with its diagnostic (Safe ignition map - loss of performance).
3. Quick cam/crank synchronization on start disabled.

Scheme 73

The sensor is located at the front of the engine in the water pipe below the throttle body. The ECT (engine coolant temperature) sensor is a thermistor used to monitor the engine coolant temperature. The engine coolant temperature sensor is vital to the correct running of the engine as a richer mixture is required at lower block temperatures for good quality starts and smooth running, leaning off as the temperature rises to maintain emissions and performance.

The sensor has an operating temperature range of -30 Degrees Celsius to 125 Degrees Celsius. When a defective coolant sensor is detected, the ECM defaults to the oil temperature sensor value.

Scheme 74

Oil temperature is monitored through a temperature sensor mounted in the oil system. This component is a NTC (negative temperature coefficient) type. The sensor is mounted next to the oil pressure sensor at the front of the engine and locates into the oil filter bracket.

Scheme 75

The oil pressure sensor is located in the oil filter bracket adjacent to the oil temperature sensor. The sensor is hardwired to the instrument cluster and is used to illuminate the oil pressure warning indicator. The sensor switches on at pressures below 24.5kPa and is closed circuit at zero oil pressure.

Scheme 76

The fuel rail temperature sensor measures the temperature of the fuel in the fuel rail. This input is then used to deliver the correct quantity of fuel to the engine. Operating Range -40 Degrees Celsius to 150 Degrees Celsius. The fuel rail temperature sensor is fitted on the rear of the right hand bank (bank A) fuel rail.

Scheme 77

The DMTL system periodically checks the evaporative system and the fuel tank for leaks when the ignition is switched off. The DMTL pump is connected to the atmospheric vent of the charcoal canister and incorporates a PTC heating element a normally open valve and a reference orifice. The DMTL pump is only operated when the ignition is switched off and is controlled by the ECM. The ECM also monitors the electric air pump operation and the normally open valve for faults. To check the fuel tank and EVAP system for leaks the ECM operates the DMTL pump and monitors the current draw. This is compared to a referenced figure established from the current draw when air is pumped through the reference orifice.

Scheme 78

The purge valve is located LH side of the engine, on a bracket which is attached to the cylinder block. The purge hose is routed from the purge valve, along the left hand side of the air intake manifold, to the elbow assembly which locates the electric throttle.

The purge hose is connected, at the right hand rear of the engine, with a quick release coupling to the purge line which runs parallel with the fuel feed line and around the rear of the fuel tank to the charcoal canister.

The purge hose continues from the purge valve and is routed to a connection on the air intake elbow assembly. The hose is connected to the elbow with a quick release connector.

The purge valve is a solenoid operated valve which is closed when de-energized. The purge valve is controlled by a 10Hz PWM signal from the ECM. When the engine operating conditions are correct, the ECM opens the purge valve which causes fuel vapor and fresh air to be drawn through the charcoal canister. The fresh air is drawn through the charcoal canister via the DMTL pump fresh air vent. Refer to Evaporative Emissions article.

Scheme 79

The air flow meter is located in the clean air duct immediately after the air filter box.

The air mass flow is determined by the cooling effect of inlet air passing over a "hot film" element contained within the device. The higher the air flow the greater the cooling effect and the lower the electrical resistance of the "hot film" element. The ECM then uses this signal from the MAF meter to calculate the air mass flowing into the engine.

The measured air mass flow is used in determining the fuel quantity to be injected in order to calculate the required air/fuel mixture required for correct operation of the engine and exhaust catalysts. Should the device fail there is a software backup strategy that will be evoked once a fault has been diagnosed.

The following symptoms may be observed if the sensor fails

1. During driving the engine RPM might dip, before recovering.
2. Difficulty in starting or start - stall.
3. Poor throttle response / engine performance.
4. Lambda control and idle speed control halted.
5. Emissions incorrect.
6. AFM signal offset

The IAT sensor is integrated into the MAF meter. It is a temperature dependent resistor (thermistor), i.e. the resistance of the sensor varies with temperature. This thermistor is a NTC type element meaning that the sensor resistance decreases as the sensor temperature increases. The sensor forms part of a voltage divider chain with an additional resistor in the ECM. The voltage from this sensor changes as the sensor resistance changes, thus relating the air temperature to the voltage measured by the ECM.

The ECM stores a 25°C default value for air temperature in the event of a sensor failure.

Scheme 80

The MAP sensor provides a voltage proportional to the absolute pressure in the intake manifold. This signal allows the load on the engine to be calculated and used within the internal calculations of the ECM. The sensor is located on the rear of the air intake manifold.

The output signal from the MAP sensor, together with the CKP and IAT sensors, is used by the ECM to calculate the amount of air induced into the cylinders. This enables the ECM to determine ignition timing and fuel injection duration values.

The MAP sensor receives a 5V supply voltage from ECM and provides an analogue signal to the ECM, which relates to the absolute manifold pressure and allows the ECM to calculate engine load. The ECM provides a ground for the sensor.

If the MAP signal is missing, the ECM will substitute a default manifold pressure reading based on crankshaft speed and throttle angle. The engine will continue to run with reduced driveability and increased emissions, although this may not be immediately apparent to the driver. The ECM will store fault codes which can be retrieved using the Integrated Diagnostic System (IDS).

Scheme 81

The V8 EMS has two knock sensors located in the V of the engine, one per cylinder bank. The sensors are connected to the ECM via a twisted pair.

The knock sensors produce a voltage signal in proportion to the amount of mechanical vibration generated at each ignition point. Each sensor monitors the related cylinder bank.

Care must be taken at all times to avoid damaging the knock sensors, but particularly during removal and fitting procedures. The recommendations regarding torque and surface preparation must be adhered to. The torque applied to the sensor and the quality of the surface preparation both have an influence over the transfer of mechanical noise from the cylinder block to the crystal.

The knock sensors incorporate a piezo-ceramic crystal. This crystal produces a voltage whenever an outside force tries to deflect it, (i.e. exerts a mechanical load on it). When the engine is running, the compression waves in the material of the cylinder block, caused by the combustion of the fuel/air mixture within the cylinders, deflect the crystal and produce an output voltage signal. The ECM uses the signals supplied by the knock sensors, in conjunction with the signal it receives from the camshaft sensor, to determine the optimum ignition point for each cylinder. The ignition point is set according to preprogrammed ignition maps stored within the ECM. The ECM is programmed to use ignition maps for 98 RON premium specification fuel. It will also function on 91 RON regular specification fuel and learn new adaptions. If the only fuel available is of poor quality, or the customer switches to a lower grade of fuel after using a high grade for a period of time, the engine may suffer slight pre-ignition for a short period. This amount of pre-ignition will not damage the engine. This situation will be evident while the ECM learns and then modifies its internal mapping to compensate for the variation in fuel quality. This feature is called adaption. The ECM has the capability of adapting its fuel and ignition control outputs in response to several sensor inputs.

The ECM will cancel closed loop control of the ignition system if the signal received from either knock sensor becomes implausible. In these circumstances the ECM will default to a safe ignition map. This measure ensures the engine will not become damaged if low quality fuel is used. The MIL will not illuminate, although the driver may notice that the engine 'pinks' in some driving conditions and displays a drop in performance and smoothness.

When a knock sensor fault is stored, the ECM will also store details of the engine speed, engine load and the coolant temperature.

Scheme 82

The V8 EMS incorporates an electric throttle control system. The electronic throttle body is located on the air intake manifold in the engine compartment. The system comprises three main components

1. Electronic throttle control valve
2. APP sensor
3. ECM

When the accelerator pedal is depressed the APP sensor provides a change in the monitored signals. The ECM compares this against an electronic "map" and moves the electronic throttle valve via a PWM control signal which is in proportion to the APP angle signal. The system is required to

1. Regulate the calculated intake air load based on the accelerator pedal sensor input signals and programmed mapping.
2. Monitor the drivers input request for cruise control operation.
3. Automatically position the electronic throttle for accurate speed control.
4. Perform all dynamic stability control throttle control interventions.
5. Monitor and carry out maximum engine and road speed cut out.
6. Provide differing responses for differing Terrain response modes.

A software strategy within the ECM enables the throttle position to be calibrated each ignition cycle. When the ignition is turned ON, the ECM performs a self test and calibration routine on the electronic throttle by closing the throttle full, then opening again. This tests the default position springs.

Scheme 83

The APP sensors are located on the accelerator pedal assembly.

The APP sensors are used to determine the driver's request for vehicle speed, acceleration and deceleration. This value is used by the ECM and the throttle is opened to the correct angle by an electric motor integrated into the throttle body.

The APP sensor signals are checked for range and plausibility. Two separate reference voltages are supplied to the pedal. Should one sensor fail, the other is used as a 'limp - home' input. In limp home mode due to an APP signal failure the ECM will limit the maximum engine speed to 2000 RPM.

Scheme 84

The stoplamp switch is mounted on the brake pedal bracket and is connected to the vehicle harness via a 4 pin multi plug.

When the brake pedal is pressed, the switch contacts close allowing a hard wired signal feed to be sent to the ECM. A stoplamp switch status message is then sent from the ECM to the ABS module on the high speed CAN bus.

Oxygen Sensors

There are four oxygen sensors located in the exhaust system. Two upstream before the catalytic converter and two down stream after the catalytic converter. The sensor monitors the level of oxygen in the exhaust gases and is used to control the fuel/air mixture. Positioning a sensor in the stream of exhaust gasses from each bank enables the ECM to control the fueling on each bank independently of the other, allowing much closer control of the air / fuel ratio and catalyst conversion efficiency.

Scheme 85

The oxygen sensors need to operate at high temperatures in order to function correctly. To achieve the high temperatures required, the sensors are fitted with heater elements that are controlled by a PWM signal from the ECM. The heater elements are operated immediately following engine start and also during low load conditions when the temperature of the exhaust gases is insufficient to maintain the required sensor temperatures. A non-functioning heater delays the sensor's readiness for closed loop control and influences emissions. The PWM duty cycle is carefully controlled to prevent thermal shock to cold sensors.

UHEGO (Universal Heated Exhaust Gas Oxygen) sensors also known as Linear or "Wide Band" sensors produces a constant voltage, with a variable current that is proportional to the oxygen content. This allows closed loop fueling control to a target lambda, i.e. during engine warm up (after the sensor has reached operating temperature and is ready for operation). This improves emission control.

The HEGO sensor uses Zirconium technology that produces an output voltage dependent upon the ratio of exhaust gas oxygen to the ambient oxygen. The device contains a Galvanic cell surrounded by a gas permeable ceramic, the voltage of which depends upon the level of O2 defusing through. Nominal output voltage of the device for l =1 is 300 to 500m volts. As the fuel mixture becomes richer (l<1) the voltage tends towards 900m volts and as it becomes leaner (l>1) the voltage tends towards 0 volts.

Sensors age with mileage, increasing their response time to switch from rich to lean and lean to rich. This increase in response time influences the ECM closed loop control and leads to progressively increased emissions. Measuring the period of rich to lean and lean to rich switching monitors the response rate of the upstream sensors.

Diagnosis of electrical faults is continually monitored in both the upstream and downstream sensors. This is achieved by checking the signal against maximum and minimum threshold, for open and short circuit conditions.

Oxygen sensors must be treated with the utmost care before and during the fitting process. The sensors have ceramic material within them that can easily crack if dropped / banged or over-torqued. The sensors must be torqued to the required figure, (40-50Nm), with a calibrated torque wrench. Care should be taken not to contaminate the sensor tip when anti-seize compound is used on the thread. The heater pins of HEGO and UHEGO sensor electrical connections are tinned and the signal pins are gold plated. Mixing up sensors could contaminate the connectors and affect system performance.

Failure Modes

1. Mechanical fitting & integrity of the sensor.
2. Sensor open circuit / disconnected.
3. Short circuit to vehicle supply or ground.
4. Lambda ratio outside operating band.
5. Crossed sensors bank A & B.
6. Contamination from leaded fuel or other sources.
7. Change in sensor characteristic.
8. Harness damage.
9. Air leak into exhaust system.

Failure Symptoms

1. Default to Open Loop fueling for the particular cylinder bank
2. High CO reading.
3. Strong smell of H02S (rotten eggs) till default condition.
4. Excess Emissions.

It is possible to fit front and rear sensors in their opposite location. However the harness connections are of different gender and color to ensure that the sensors cannot be incorrectly connected. In addition to this the upstream sensors have holes around the end of the shroud, whereas the down stream sensors have holes arranged along the length the shroud.

Scheme 86

The Generator has a multifunction voltage regulator for use in a 14V charging system with 6÷12 zener diode bridge rectifiers.

The ECM monitors the load on the electrical system via PWM signal and adjusts the generator output to match the required load. The ECM also monitors the battery temperature to determine the generator regulator set point. This characteristic is necessary to protect the battery; at low temperatures battery charge acceptance is very poor so the voltage needs to be high to maximize any rechargeability, but at high temperatures the charge voltage must be restricted to prevent excessive gassing of the battery with consequent water loss.

The Generator has a smart charge capability that will reduce the electrical load on the Generator reducing torque requirements, this is implemented to utilize the engine torque for other purposes. This is achieved by monitoring three signals to the ECM

1. Generator sense (A sense), measures the battery voltage at the CJB.
2. Generator communication (Alt Com) communicates desired Generator voltage set point from ECM to Generator.
3. Generator monitor (Alt Mon) communicates the extent of Generator current draw to ECM. This signal also transmits faults to the ECM which will then sends a message to the instrument pack on the CAN bus to illuminate the charge warning lamp.

Scheme 87

The engine has 8 fuel injectors (one per cylinder), each injector is directly driven by the ECM. The injectors are fed by a common fuel rail as part of a 'returnless' fuel system. The fuel rail pressure is regulated to 4.5 bar by a fuel pressure regulator which is integral to the fuel pump module, within the fuel tank. The injectors can be checked by resistance checks. There is a fuel pressure test Schrader valve attached to the fuel rail on the front LH side for fuel pressure testing purposes. The ECM monitors the output power stages of the injector drivers for electrical faults.

The injectors have a resistance of 13.8 Ohms ± 0.7 Ohms @ 20 Degrees Celsius.

Scheme 88

The V8 engine is fitted with eight plug-top coils that are driven directly by the ECM. This means that the ECM, at the point where sufficient charge has built up, switches the primary circuit of each coil and a spark is produced in the spark plug. The positive supply to the coil is fed from a common fuse. Each coil contains a power stage to trigger the primary current. The ECM sends a signal to each of the coils power stage to trigger the power stage switching. Each bank has a feedback signal that is connected to each power stage. If the coil power stage has a failure the feedback signal is not sent, causing the ECM to store a fault code appropriate to the failure.

The ECM calculates the dwell time depending on battery voltage and engine speed to ensure constant secondary energy. This ensures sufficient secondary (spark) energy is always available, without excessive primary current flow thus avoiding overheating or damage to the coils.

The individual cylinder spark timing is calculated from a variety of inputs

1. Engine speed and load.
2. Engine temperature.
3. Knock control.
4. Auto gearbox shift control.
5. Idle speed control.

Fuel Pump Relay

The V8 engine has a returnless fuel system. The system pressure is maintained at a constant 4 bar (59 Psi), with no reference to intake manifold pressure. The fuel is supplied to the injectors from a fuel pump fitted within the fuel tank. The electrical supply to this fuel pump is controlled by the ECM via a relay and an Inertia Switch which will turn the fuel off upon a vehicle impact. The fuel system is pressurized as soon as the ECM is powered up, the pump is then switched off until engine start has been achieved.

Cooling Fan Control

The ECM controls an electric fan to provide engine cooling. The ECM supplies the fan with a PWM signal that controls the speed of the fan, thus providing the correct amount of cooling fan speed and airflow. The EMS uses a Hall effect sensor to determine the fan speed.

Variable Valve Control (VVC)

Variable valve timing is used on the V8 engine to enhance low and high speed engine performance and idle speed quality.

For each inlet camshaft the VVC system comprises

1. VVC unit
2. Valve timing solenoid

The VVC system alters the phase of the intake valves relative to the fixed timing of the exhaust valves, to alter

1. The mass of air flow to the cylinders.
2. The engine torque response.
3. Emissions.

The VVC unit uses a vane type device to control the camshaft angle. The system operates over a range of 48 degrees and is advanced or retarded to its optimum position within this range.

The VVC system is controlled by the ECM based on engine load and speed along with engine oil temperature to calculate the appropriate camshaft position.

The VVC system provides the following advantages

1. Reduced engine emissions and improved fuel consumption which in turn improves the engines internal EGR effect over a wider operating range.
2. Enhanced full load torque characteristics.
3. Improved fuel economy through optimized torque over the engine speed range.

Scheme 89

The VVC unit is a hydraulic actuator mounted on the end of the inlet camshaft. The unit advances or retards the camshaft timing to alter the camshaft to crankshaft phase. The ECM controls the VVC timing unit via a oil control solenoid. The oil control solenoid routes oil pressure to the advance or retard chambers either side of the vanes within the VVC unit.

The VVC unit is driven by the primary drive chain and rotates relative to the exhaust camshaft. When the ECM requests a retard in camshaft timing the oil control solenoid is energized which moves the shuttle valve in the solenoid to the relevant position allowing oil pressure to flow out of the advance chambers in the VVC unit whilst simultaneously allowing oil pressure into the retard chambers.

The ECM controls the advancing and retarding of the VVC unit based on engine load and speed. The ECM sends an energize signal to the oil control solenoid until the desired VVC position is achieved. When the desired VVC position is reached, the energizing signal is reduced to hold the oil control solenoid position and consequently desired VVC position. This function is under closed loop control and the ECM can sense any variance in shuttle valve oil pressure via the camshaft position sensor and can adjust the energizing signal to maintain the shuttle valve hold position.

VVC operation can be affected by engine oil temperature and properties. At very low oil temperatures the movement of the VVC mechanism will be slow due to the high viscosity of the oil. While at high oil temperatures the low oil viscosity may impair the VVC operation at low oil pressures. The oil pump has the capacity to cope with these variations in oil pressure while an oil temperature sensor is monitored by the ECM to provide oil temperature feedback. At extremely high oil temperatures the ECM may limit the amount of VVC advance in order to prevent the engine from stalling when returning to idle speed.

VVC does not operate when engine oil pressure is below 1.25 bar. This is because there is insufficient pressure to release the VVC units internal stopper pin. This occurs when the engine is shut down and the VVC unit has returned to the retarded position. The stopper pin locks the VVC unit to the camshaft to ensure camshaft stability during the next start up.

Scheme 90

Valve Timing Solenoid

The valve timing solenoid controls the position of the shuttle valve in the bush carrier. A plunger on the solenoid extends when the solenoid is energized and retracts when the solenoid is de-energized.

When the valve timing solenoids are de-energized, the coil springs in the bush carriers position the shuttle valves to connect the valve timing units to drain. In the valve timing units, the return springs hold the ring pistons and gears in the retarded position. When the valve timing solenoids are energized by the ECM, the solenoid plungers position the shuttle valves to direct engine oil to the valve timing units. In the valve timing units, the oil pressure overcomes the force of the return springs and moves the gears and ring pistons to the advanced position. System response times are 1.0 second maximum for advancing and 0.7 second maximum for retarding. While the valve timing is in the retarded mode, the ECM produces a periodic lubrication pulse. This momentarily energizes the valve timing solenoids to allow a spurt of oil into the valve timing units. The lubrication pulse occurs once every 5 minutes.

Scheme 91

The EGR valve is an electrically controlled valve that allows burned exhaust gas to be recirculated back into the engine. The EGR valve consists of a stepper motor that opens and closes the valve in steps. Since exhaust gas has much less oxygen than air, it is basically inert. It takes the place of air in the cylinder and reduces combustion temperature. As the combustion temperature is reduced, so are the oxides of nitrogen (NOx).

The EGR valve is located on the intake manifold with a pipe connecting the exhaust manifold to the valve. Connection between the sensor and the harness is via a six-way connector.

Scheme 92

The Fuel Pump Driver Module (FPDM) is located in the rear LH quarter adjacent to the parking aid control module.

The fuel pump is control by the ECM. The ECM sends a PWM signal to the FPDM, the frequency of the signal determines the duty cycle of the pump. The PWM signal to the pump represents half the ON time of the pump. If the ECM transmits a 50% on time the FPDM drives the pump at 100%. If the ECM transmits a 5% ON time the FPDM drives the pump at 10%. The FPDM will only turn the fuel pump ON if it receives a valid signal between 4% and 50%. When The ECM requires the fuel pump to be turned OFF the ECM transmits a duty cycle signal of 75%.

The status of the FPDM is monitored by the ECM. Any errors can be retrieved from the ECM using IDS. The FPDM cannot be interrogated for diagnostic purposes.

The MAP controls The FPDM in response to inputs from the fuel rail pressure sensor, MAP and the MAF/IAT sensor.

Scheme 93

The fuel rail pressure sensor is located on top of the fuel rail adjacent to the fuel inlet. The fuel rail pressure sensor measures the pressure of the fuel in the fuel rail. This input is then used by the FPDM to control the amount of fuel delivered to the fuel rail. The fuel rail pressure sensor is a pressure transducer device. A vacuum pipe connects to the intake manifold for manifold pressure. The ECM receives a voltage from the FRP sensor which is proportional to the fuel pressure in the fuel injection supply manifold.

Scheme 94

The ECM is connected to ignition switch I and II. When the ignition is turned on 12V is applied to the Ignition Sense input. The ECM then starts its power up routines and turns on the ECM main relay; the main power to the ECM and it's associated system components. When the ignition is turned OFF the ECM will maintain its powered up state for up to 20 minutes while it initiates its power down routine and on completion will turn off the ECM main relay. The ECM will normally power down in approximately 60 seconds, do not disconcert the battery until the ECM is completely powered down.

Secondary Air Injection

The secondary air injection system comprises

1. SAI pump
2. SAI valve
3. Associated pipes
4. SAI Manifold Absolute Pressure (MAP) sensor (NAS only)

The ECM controls the SAI pump and SAI valve with a PWM signal and on NAS vehicles measures the system pressure via the MAP sensor. Refer to Engine Emission Control article.

CONTROL DIAGRAM SHEET 1 of 3

Note. A = Hardwired connection

CONTROL DIAGRAM SHEET 2 of 3

Note. A = Hardwired connection

CONTROL DIAGRAM SHEET 3 of 3

Note. D = High speed CAN bus; N=Medium speed CAN bus; O = LIN (local interconnect network) bus

ECM Adaptions

The ECM has the ability to adapt the values it uses to control certain outputs. This capability ensures the EMS can meet emissions legislation and improve the refinement of the engine throughout its operating range.

The components which have adaptions associated with them are

1. The APP sensor
2. The H02S
3. The MAF/IAT sensor
4. The CKP sensor
5. Electric throttle body.

UHEGO/HEGO and MAF/IAT Sensor

There are several adaptive maps associated with the fueling strategy. Within the fueling strategy the ECM calculates short-term adaptions and long term adaptions. The ECM will monitor the deterioration of the oxygen sensors (HEGO and UHEGO) over a period of time. It will also monitor the current correction associated with the sensors.

The ECM will store a fault code in circumstances where an adaption is forced to exceed its operating parameters. At the same time, the ECM will record the engine speed, engine load and intake air temperature.

CKP Sensor

The characteristics of the signal supplied by the CKP sensor are learned by the ECM. This enables the ECM to set an adaption and support the engine misfire detection function. Due to the small variation between different flywheels and different CKP sensors, the adaption must be reset if either component is renewed, or removed and refitted. It is also necessary to reset the flywheel adaption if the ECM is renewed or replaced. The ECM supports four flywheel adaptions for the CKP sensor. Each adaption relates to a specific engine speed range. The engine speed ranges are detailed in the table below

Misfire Detection

Legislation requires that the ECM must be able to detect the presence of an engine misfire. It must be able to detect misfires at two separate levels. The first level is a misfire that could lead to the vehicle emissions exceeding 1.5 times the Federal Test Procedure (FTP) requirements for the engine. The second level is a misfire that may cause catalyst damage.

The ECM monitors the number of misfire occurrences within two engine speed ranges. If the ECM detects more than a predetermined number of misfire occurrences within either of these two ranges, over two consecutive journeys, the ECM will record a fault code and details of the engine speed, engine load and engine coolant temperature. In addition, the ECM monitors the number of misfire occurrences that happen in a 'window' of 200 engine revolutions. The misfire occurrences are assigned a weighting according to their likely impact on the catalysts. If the number of misfires exceeds a certain value, the ECM stores catalyst-damaging fault codes, along with the engine speed, engine load and engine coolant temperature.

The signal from the crankshaft position sensor indicates how fast the poles on the flywheel are passing the sensor tip. A sine wave is generated each time a pole passes the sensor tip. The ECM can detect variations in flywheel speed by monitoring the sine wave signal supplied by the crankshaft position sensor.

By assessing this signal, the ECM can detect the presence of an engine misfire. At this time, the ECM will assess the amount of variation in the signal received from the CKP and assigns a roughness value to it. This roughness value can be viewed within the real time monitoring feature, using IDS. The ECM will evaluate the signal against a number of factors and will decide whether to count the occurrence or ignore it. The ECM can assign a roughness and misfire signal for each cylinder, (i.e. identify which cylinder is misfiring).