Part 1
Electronic Engine Controls
NOTE:
A = Hardwired, D = High speed CAN (controller area network) bus, N = Medium speed CAN (controller area network) bus, O = LIN (local interconnect network) bus
CONTROL DIAGRAM SHEET 1 OF 3
CONTROL DIAGRAM SHEET 2 OF 3
CONTROL DIAGRAM SHEET 3 OF 3
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 six 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 ECM (engine control module) 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.).
System Inputs
The EMS has the following inputs:
- RCM (restraints control module)
- Park/neutral switch
- Ignition coil feedback
- Fuel rail temperature
- MAF (mass air flow)
- Engine speed
- Camshaft position
- Driver demand
- Brake pedal position switch
- Speed control switches
- Generator load
- HO2S (heated oxygen sensor) pre catalyst
- HO2S (heated oxygen sensor) post catalyst
- Throttle position
- Cooling fan speed
- Ignition switch
- Knock sensors
- MAP (manifold absolute pressure)
- ECT (engine coolant temperature)
- Engine oil temperature
- EOP (engine oil pressure)
- Fuel pressure
- Fuel temperature
System Outputs
The EMS has the following outputs:
- Throttle Actuator
- Brake vacuum pump relay
- Ignition coils
- Oxygen sensor heaters
- Fuel injectors
- Purge Valve
- Engine Cooling Fan
- Fuel pump relay
- Starter Relay
- ECM (engine control module) Main Relay
- Generator Control
- Fuel tank leakage detection
ECM Adaptions
The ECM (engine control module) 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:
- The APP (accelerator pedal position) sensor
- The oxygen sensors
- The MAF (mass air flow)/IAT (intake air temperature) sensor
- The CKP (crankshaft position) sensor
- The Electric throttle body.
Oxygen Sensors and MAF/AT Sensor
There are several adaptive maps associated with the fueling strategy. Within the fueling strategy the ECM (engine control module) calculates short-term adaptions and long term adaptions. The ECM (engine control module) will monitor the deterioration of the oxygen sensors over a period of time. It will also monitor the current correction associated with the sensors.
The ECM (engine control module) will store a fault code in circumstances where an adaption is forced to exceed its operating parameters. At the same time, the ECM (engine control module) will record the engine speed, engine load and intake air temperature.
Crankshaft Position Sensor
The characteristics of the signal supplied by the CKP (crankshaft position) sensor is learnt by the ECM (engine control module). This enables the ECM (engine control module) to set an adaption and support the engine misfire detection function. Due to the small variation between different flywheels and different CKP (crankshaft position) 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 (engine control module) is renewed or replaced. The ECM (engine control module) supports four flywheel adaptions for the CKP (crankshaft position) 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 (engine control module) 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 (engine control module) sensor monitors the number of misfire occurrences within two engine speed ranges. If the ECM (engine control module) detects more than a predetermined number of misfire occurrences within either of these two ranges, over two consecutive journeys, the ECM (engine control module) will record a fault code and details of the engine speed, engine load and engine coolant temperature. In addition, the ECM (engine control module) 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 (engine control module) stores catalyst-damaging fault codes, along with the engine speed, engine load and engine coolant temperature.
The signal from the CKP (crankshaft position) 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 (engine control module) can detect variations in flywheel speed by monitoring the sine wave signal supplied by the CKP (crankshaft position) sensor.
By assessing this signal, the ECM (engine control module) can detect the presence of an engine misfire. At this time, the ECM (engine control module) will assess the amount of variation in the signal received from the CKP (crankshaft position) and assigns a roughness value to it. This roughness value can be viewed within the real time monitoring feature, using a Land Rover approved diagnostic system. The ECM (engine control module) will evaluate the signal against a number of factors and will decide whether to count the occurrence or ignore it. The ECM (engine control module) can assign a roughness and misfire signal for each cylinder, (i.e. identify which cylinder is misfiring).
Diagnostics
The ECM (engine control module) stores faults as DTC (diagnostic trouble code), referred to as 'P' codes. The 'P' codes are defined by OBD (on-board diagnostic) legislation and, together with their associated environmental and freeze frame data, can be read using a third party scan tool or a Land Rover approved diagnostic system. A Land Rover approved diagnostic system can also read real time data from each sensor, the adaptive values currently being employed and the current fueling, ignition and idle settings.
Engine Control Module
The ECM (engine control module) is located in the engine bay attached to the bulkhead. On LHD (left-hand drive) vehicles the ECM (engine control module) is located on the RH (right-hand) side of the compartment behind the BJB (battery junction box). On RHD (right-hand drive) vehicles the ECM (engine control module) is located on the LH (left-hand) side of the engine compartment.
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.).
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
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 ECT (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.PTC (positive temperature coefficient)
Tank Leakage Detection-NAS ONLY
The tank leakage detection system periodically checks the evaporative system and the fuel tank for leaks when the ignition is switched off. The tank leakage detection 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 tank leakage detection 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 tank leakage detection 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
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 tank leakage detection pump fresh air vent.NTC (negative temperature coefficient)
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/Intake 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.