Part 1
Electronic Engine Controls
COMPONENT LOCATION (SHEET 1 OF 2)
Electronic Engine Controls - Component Location (Sheet 1 Of 2):
COMPONENT LOCATION (SHEET 2 OF 2)
Electronic Engine Controls - Component Location (Sheet 2 Of 2):
GENERAL
The V8 4.4 Liter engine is controlled by an ECM (engine control module) manufactured by DENSO. The Engine Management System (EMS) controls the following:
^ Engine fueling
^ Ignition timing
^ Closed loop fueling
^ Knock control
^ Idle speed control
^ Emission control
^ OBD (on-board diagnostic)
^ Interface with the immobilization system
^ Speed control
The ECM (engine control module) controls the engine fueling by providing sequential fuel injection to all cylinders. Ignition is controlled by a direct ignition system, provided by eight plug top coils. The ECM (engine control module) is able to detect and correct for ignition knock on each cylinder and adjust the ignition timing for each cylinder to achieve optimum performance.
The ECM (engine control module) uses a torque-based strategy to generate the torque required by the driver and other vehicle control modules. The EMS uses various sensors to determine the torque required from the engine. The EMS also interfaces with other vehicle electronic control modules's, via the CAN (controller area network) bus, to obtain additional information (e.g. road speed from the ABS (anti-lock brake system) control module). The EMS processes these signals and decides how much torque to generate. Torque is then generated by using various actuators to supply air, fuel and spark to the engine (electronic throttle, injectors, coils, etc.).
ENGINE CONTROL MODULE (ECM)
The ECM (engine control module) is located in the E-Box on the RH (right-hand) side of the engine compartment at the front.
System ECM (engine control module) has the following inputs:
^ RCM (restraints control module)
^ Park/neutral switch
^ Ignition coil feedback x2
^ Fuel rail temperature
^ Mass air flow/intake air temperature
^ Engine speed
^ Intake cam position
^ Driver demand
^ Brake pedal switch
^ Generator load
^ UHEGO
^ HEGO
^ Throttle position
^ Cooling fan speed
^ Ignition switch position
^ Knock sensors
^ MAP (manifold absolute pressure) sensor
^ Coolant temperature
^ Engine oil temperature
The ECM (engine control module) outputs to the following:
^ Throttle actuator
^ Brake vacuum pump relay
^ Ignition coils (x8)
^ Oxygen sensor heaters (4)
^ Fuel injectors (8)
^ EGR (exhaust gas recirculation) valve
^ Variable Valve Timing Oil Valves (2)
^ Purge valve
^ Engine cooling fan
^ Fuel pump relay
^ Starter relay
^ EMS Main relay
^ Diagnostic Module Tank Leakage (DMTL) (NAS Only)
^ E-box fan
CRANKSHAFT POSITION SENSOR (CKP)
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 (engine control module). The sensor produces the signal which enables the ECM (engine control module) 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° advance in timing will occur, as the electronics within the ECM (engine control module) 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 60 degrees BTDC (before top dead center) No.1 cylinder. Because of the crankshaft sensor's orientation, the target wheel uses windows machined 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 (engine control module) transmits the engine speed to other vehicle control modules on CAN (controller area network).
CAMSHAFT POSITION SENSOR (CMP)
Two sensors are located at the rear of the engine, in the cylinder head (one per bank), above the rear cylinders. This is a Variable Reluctor Sensor (VRS) 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 variable cam intake is parked in the retarded position and can advance up to 48 degrees.
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:
^ Variable intake cam timing
^ Cylinder recognition
^ Enabling sequential fuel injection
^ Knock control
^ Cylinder identification for diagnostic purposes.
Failure symptoms include:
^ Ignition timing reverting to the base mapping, with no cylinder correction.
^ Active knock control is disabled, along with its diagnostic (Safe ignition map - loss of performance).
^ Quick cam/crank synchronization on start disabled.
^ Variable cam timing is disabled
ENGINE COOLANT TEMPERATURE SENSOR (ECT)
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 -40 Degrees Celsius to 119 Degrees Celsius. When a defective coolant sensor is detected, the ECM (engine control module) uses the oil temperature sensor value.
DIAGNOSTIC MONITORING OF TANK LEAKAGE (DMTL) - NAS ONLY
Charcoal Canister with DMTL Pump (NAS only)
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 cannister and incorporates a PTC (positive temperature coefficient) 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 (engine control module). The ECM (engine control module) 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 (engine control module) 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.
PURGE VALVE
Purge Valve and Hoses location
The purge valve is located at the rear of the engine on a bracket which is attached to the transmission bell housing. The purge valve is a solenoid operated valve which is closed when de-energized. The purge valve is controlled by a 10Hz PWM (pulse width modulation) signal from the ECM (engine control module). When the engine operating conditions are correct, the ECM (engine control module) opens the purge valve which causes fuel vapor and fresh air to be drawn through the charcoal cannister. The fresh air is drawn through the charcoal cannister via the DMTL pump fresh air vent.
ENGINE OIL TEMPERATURE SENSOR
Oil temperature is monitored through a temperature sensor mounted in the oil system. This component is a NTC (negative temperature coefficient). The sensor is mounted next to the oil pressure sensor at the front of the engine and locates into the oil filter bracket.
FUEL RAIL TEMPERATURE SENSOR
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.
MASS AIR FLOW/INLET AIR TEMPERATURE SENSOR (MAF/IAT)
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 intake 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 (engine control module) then uses this signal from the Mass Air Flow 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 maintain the stoichiometric 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:
^ During driving the engine RPM might dip, before recovering.
^ Difficulty in starting or start - stall.
^ Poor throttle response/engine performance.
^ Lambda control and idle speed control halted.
^ Emissions incorrect.
^ AFM signal offset
The IAT (intake air temperature) sensor is integrated into the MAF (mass air flow) sensor. It is a temperature dependent resistor (thermistor), i.e. the resistance of the sensor varies with temperature. This thermistor is a NTC (negative temperature coefficient) 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 (engine control module). The voltage from this sensor changes as the sensor resistance changes, thus relating the air temperature to the voltage measured by the ECM (engine control module).
The ECM (engine control module) stores a 25 Degrees Celsius default value for air temperature in the event of a sensor failure.
MANIFOLD ABSOLUTE PRESSURE SENSOR (MAP)
The MAP (manifold absolute pressure) 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 (engine control module). The sensor is located on the rear of the air intake manifold.
Pin No Description
1 MAP (manifold absolute pressure) signal
2 Sensor supply
3 Not used
4 Sensor ground
The output signal from the MAP (manifold absolute pressure) sensor, together with the CKP (crankshaft position) and IAT (intake air temperature) sensors, is used by the ECM (engine control module) to calculate the amount of air induced into the cylinders. This enables the ECM (engine control module) to determine ignition timing and fuel injection duration values.
The MAP (manifold absolute pressure) sensor receives a 5V supply voltage from pin 48 of ECM (engine control module) connector C0634 and provides an analogue signal to pin 69 of ECM (engine control module) connector C0634, which relates to the absolute manifold pressure and allows the ECM (engine control module) to calculate engine load. The ECM (engine control module) provides a ground for the sensor via pin 11 of ECM (engine control module) connector C0634.
If the MAP (manifold absolute pressure) signal is missing, the ECM (engine control module) will substitute a default manifold pressure reading based on crankshaft speed and throttle angle. The engine will continue to run with reduced drivability and increased emissions, although this may not be immediately apparent to the driver. The ECM (engine control module) will store fault codes which can be retrieved using T4.
KNOCK SENSORS
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 (engine control module) 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.
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 signals are supplied to the ECM (engine control module), which compares them with `mapped' signals stored in memory. From this, the ECM (engine control module) can determine when detonation occurs on individual cylinders. When detonation is detected, the ECM (engine control module) retards the ignition timing on that cylinder for a number of engine cycles, then gradually returns it to the original setting.
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 ECM (engine control module) 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 (engine control module). The ECM (engine control module) 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 (engine control module) learns and then modifies its internal mapping to compensate for the variation in fuel quality. This feature is called adaption. The ECM (engine control module) has the capability of adapting its fuel and ignition control outputs in response to several sensor inputs.
The ECM (engine control module) will cancel closed loop control of the ignition system if the signal received from either knock sensor becomes implausible. In these circumstances the ECM (engine control module) will default to a safe ignition map. This measure ensures the engine will not become damaged if low quality fuel is used. The MIL lamp 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 (engine control module) will also store details of the engine speed, engine load and the coolant temperature.
ELECTRONIC THROTTLE
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:
^ Electronic throttle control valve
^ APP (accelerator pedal position)
^ ECM (engine control module)
When the accelerator pedal is depressed the APP (accelerator pedal position) sensor provides a change in the monitored signals. The ECM (engine control module) compares this against an electronic map and moves the electronic throttle valve via a PWM (pulse width modulation) control signal which is in proportion to the APP (accelerator pedal position) angle signal. The system is required to:
^ Regulate the calculated intake air load based on the accelerator pedal sensor input signals and programmed mapping.
^ Monitor the drivers input request for cruise control operation.
^ Automatically position the electronic throttle for accurate cruise control.
^ Perform all dynamic stability control throttle control interventions.
^ Monitor and carry out maximum engine and road speed cut out.
A software strategy within the ECM (engine control module) enables the throttle position to be calibrated each ignition cycle. When the ignition is turned OFF, the ECM (engine control module) performs a self test and calibration routine on the electronic throttle by closing the throttle fully. The power is then removed and the ECM (engine control module) checks that the throttle returns to the reference position under the pressure from the spring.
ACCELERATOR PEDAL POSITION SENSOR (APP)
The APP (accelerator pedal position) sensor is located in a plastic housing which is integral with the throttle pedal. The housing is injection molded and provides location for the APP (accelerator pedal position) sensor. The sensor is mounted externally on the housing and is secured with two Torx screws. The external body of the sensor has a six pin connector which accepts a connector on the vehicle wiring harness.
The sensor has a spigot which protrudes into the housing and provides the pivot point for the pedal mechanism. The spigot has a slot which allows for a pin, which is attached to the sensor potentiometers, to rotate through approximately 90 degrees, which relates to pedal movement. The pedal is connected via a link to a drum, which engages with the sensor pin, changing the linear movement of the pedal into rotary movement of the drum. The drum has two steel cables attached to it. The cables are secured to two tension springs which are secured in the opposite end of the housing. The springs provide 'feel' on the pedal movement and require an effort from the driver similar to that of a cable controlled throttle. A detente mechanism is located at the forward end of the housing and is operated by a ball located on the drum. At near maximum throttle pedal movement, the ball contacts the detente mechanism. A spring in the mechanism is compressed and gives the driver the feeling of depressing a 'kickdown' switch when full pedal travel is achieved.
The APP (accelerator pedal position) 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 (accelerator pedal position) signal failure the ECM (engine control module) will limit the maximum engine speed to 2000 rpm.
APP (accelerator pedal position) Sensor Output Graph
The APP (accelerator pedal position) sensor has two potentiometer tracks which each receive a 5V input voltage from the ECM (engine control module). Track 1 provides an output of 0.5V with the pedal at rest and 2.0V at 100% full throttle. Track 2 provides an output of 0.5V with the pedal at rest and 4.5V at 100% full throttle. The signals from the two tracks are used by the ECM (engine control module) to determine fueling for engine operation and also by the ECM (engine control module) and the TCM (transmission control module) to initiate a kickdown request for the automatic transmission.
The ECM (engine control module) monitors the outputs from each of the potentiometer tracks and can determine the position, rate of change and direction of movement of the throttle pedal. The 'closed throttle' position signal is used by the ECM (engine control module) to initiate idle speed control and also overrun fuel cut-off.