Part 1
Electronic Engine Controls - 3.2L
COMPONENT LOCATION SHEET 1 OF 2
COMPONENT LOCATION SHEET 2 OF 2
OVERVIEW
The Engine Control Module (ECM) controls the following:
^ Engine fueling
^ Ignition timing
^ Closed loop fueling
^ Knock control
^ Idle speed control
^ Emission control
^ On Board Diagnostics
^ Speed control.
The ECM controls engine fueling by providing sequential fuel injection to all cylinders. Ignition is controlled by a direct ignition system, provided by 6 plug top coils. The ECM 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 uses a torque-based strategy to generate the torque required by the driver and other vehicle control modules. The ECM uses various sensors to determine the torque required from the engine. The ECM also interfaces with other vehicle electronic control modules via the high speed Controller Area Network (CAN) bus, to obtain additional information (for example road speed from the Anti-lock Brake System (ABS) module). The ECM 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.
The ECM also uses an electronic throttle system which comprises the electric throttle assembly and an Accelerator Pedal Position (APP) sensor.
The ECM also interfaces with the immobilization system to help prevent the vehicle being started without proper authorization.
CONTROL DIAGRAM SHEET 1 OF 2
CONTROL DIAGRAM SHEET 2 OF 2
ENGINE CONTROL MODULE (ECM)
The ECM is located on a bracket in a central position on the engine compartment firewall. The ECM is attached to a housing and secured with 4 screws. The housing is located in the bracket and locked in position.
The ECM is supplied with battery voltage from fuses located in the BJB. A permanent battery supply is provided to ensure adaptive data is not lost when the engine is switched off.
A regulator, located within the ECM, supplies a 5 V current to internal components such as the micro-processor unit. Other components or functions requiring full battery voltage are controlled by external relays or internal power stages.
The micro-processor within the ECM receives signals from different components and control modules and uses a program within the ECM software to interpret the signal information and issue signals which relate to how the engine components and functions should be controlled.
The ECM receives inputs from the following:
^ CMP sensors
^ CKP sensor
^ Fuel rail pressure sensor
^ MAF sensor
^ Knock sensors
^ Fuel rail temperature/pressure sensor
^ ECT sensor
^ Engine oil level/temperature sensor
^ Manifold Absolute Pressure (MAP) sensor
^ Electric throttle - Throttle Position (TP) sensor
^ APP sensor
^ Fuel tank leakage monitoring module (NAS only)
^ Cooling fan control
^ Heated Oxygen sensors (HO2S)
^ Stop lamp switch (via Central Junction Box (CJB))
^ Speed control inhibit switch
^ Intake Air Temperature (IAT) sensor
^ Ambient Air Temperature (AAT) sensor
^ Transmission Control Module (TCM).
The ECM sends outputs to the following:
^ Main relay
^ Air Conditioning (A/C) relay
^ Fuel injectors
^ Ignition coils
^ Engine cooling fan control
^ Electric throttle
^ Electric fuel pump driver module
^ Variable Camshaft Timing (VCT) solenoids
^ Starter relay control
^ Variable intake manifold control valves
^ Variable inlet cam profile switching solenoid valves
^ Transmission Control Module (TCM).
SENSORS
The ECM optimizes engine performance by interpreting signals from numerous vehicle sensors and other inputs. Some of these signals are produced by the actions of the driver, some are supplied by sensors located on and around the engine and some are supplied by other vehicle systems.
Camshaft Position (CMP) Sensor
Two CMP sensors are located in the camshaft housing at the Left Hand (LH) end of the engine. The sensors are located in a hole in the housing and are secured with a screw. There is a CMP sensor for each camshaft.
The CMP sensors monitor the position of the camshafts to establish ignition timing order, fuel injection triggering and for accurate Variable Camshaft Timing (VCT) operation. The ECM can also use the CMP sensors to determine which cylinder has a misfire or knock using the CMP signal output.
The CMP sensor is a Hall-effect sensor which switches a 5 V supply from the ECM on and off. The supply is switched when teeth machined onto a pulse wheel on the camshaft pass by the tip of the sensor. The teeth are of differing shapes, so the ECM can determine the exact position of the camshaft at any time. When one of the teeth passes by the sensor tip, a signal is transmitted to the ECM which can vary between 0 and 5 V. The signal is high when a tooth is directly adjacent to the sensor and is low when the tooth is away from the sensor.
Failure of one or both of the sensors will result in the ECM using a default map for ignition timing and knock control will be disabled.
The ECM monitors the sensor for correct function and can diagnose and store fault codes for sensor faults. These can be retrieved using a Land Rover approved diagnostic system.
Crankshaft Position (CKP) Sensor
The CKP sensor is located on the forward side of the transmission torque converter housing, in line with the engine flywheel. The sensor is secured with a bolt into a bracket attached to the gear housing. A reluctor ring is fitted to the outer diameter of the crankshaft flexplate and the sensor reacts to the gaps in the reluctor ring to determine engine speed and position information. The sensor has 2 wires from the ECM sensor ground and a feedback signal.
The CKP sensor is an inductive type sensor which produces a sinusoidal output voltage signal. This voltage is induced by the proximity of the moving reluctor ring gaps, which excite the magnetic flux around the tip of the sensor when each gap passes. This output voltage will increase in magnitude and frequency as the engine speed rises determined by an increase in the speed at which the gaps on the reluctor ring pass the sensor. The signal voltage can be as low as 0.1 V at low engine speeds and up to 100 V at high engine speeds. The ECM does not react to the output voltage (unless the voltage is extremely low or high), instead it measures the time intervals between each pulse (signal frequency). The signal is determined by the number of gaps passing the sensor, and the speed at which they pass. The reluctor ring has 2 gaps missing to give the ECM a synchronization point and determine the position of the crankshaft. The CKP sensor signal is also used for misfire detection.
The signal produced by the CKP sensor is critical to engine running. Failure of the sensor when the engine is running will result in the engine stopping immediately. The engine can be restarted using signals from the CMP sensors but the engine speed will be limited to 3000 rpm and the Malfunction Indicator Lamp (MIL) will be illuminated.
The ECM monitors the sensor for correct function and can diagnose and store fault codes for sensor faults. These can be retrieved using a Land Rover approved diagnostic system.
Fuel Rail Pressure/Temperature Sensor
The fuel rail pressure/temperature sensor is located on the LH end of the fuel rail. The ECM supplies the combined pressure and temperature sensor with a 5 V reference voltage and a ground and measures the returned signals for pressure and temperature.
Fuel pressure
The fuel pressure sensor is a piezo resistor type sensor. The sensor receives a 5 V reference voltage from the ECM and produces an analogue signal of between 0 and 5 V depending on the pressure sensed. Low pressure gives a low voltage output and consequently high pressure gives a higher voltage output. The ECM uses this pressure signal to adjust the fuel pump module output pressure by sending controlling signals to the FPDM and for injector timing.
The ECM monitors the fuel pressure sensor for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system. Sensor operation can also be checked using a Land Rover approved diagnostic system to check fuel pressure. If no fuel pressure is in the fuel rail, the sensor will read and output atmospheric pressure.
Fuel Temperature
The fuel temperature sensor is a Negative Temperature Co-efficient (NTC) sensor. The sensing thermistor element resistance decreases as the sensor temperature increases. The ECM supplies the sensor with a 5 V reference voltage and a ground and measures the returned signal as a temperature.
The resistance in the sensor changes with fuel temperature. A low fuel temperature will result in a high voltage being returned to the ECM and high fuel temperature will return a low voltage reading of between 0 - 5V.
The ECM monitors the fuel temperature sensor for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system. The ECM uses the ECT temperature signal as a default but only up to a maximum of 100 degrees C (212 degrees F).
Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor
The MAF/IAT sensor is located in the outlet pipe from the air cleaner housing. The combined MAF/IAT functions are connected to the ECM on separate wires. The sensor has an extended moulding which is located in a central position the air flow through the air cleaner housing outlet pipe, through which the air flow and temperature are measured.
Mass Air Flow (MAF) Sensor
The MAF sensor measures the mass of air being drawn into the engine. The air mass is calculated by the cooling effect of inlet air passing over a 'hot film' element contained within the sensor. The higher the air flow, the greater the cooling effect on the element which in turn lowers the electrical resistance of the 'hot film' element. The ECM uses this resistance value to calculate the air mass or volume of air flowing into the engine.
The MAF sensor receives a battery voltage supply via the ECM and the main relay. The ECM provides a ground and a signal path for the resistance signal from the 'hot film' sensor. The analogue signal from the MAF sensor varies between 0.5 and 5 V. Low air flow gives a low voltage and high air flow gives a high voltage.
The MAF signal is used by the ECM to determine:
^ the correct fuel quantity (injection period) to maintain the correct air/fuel ratio required for correct operation of the engine and the catalysts
^ the ignition timing
^ the engine load.
The ECM monitors the MAF sensor for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system.
Intake Air Temperature (IAT) Sensor
The IAT sensor measures the temperature of the intake air entering the engine. The sensor is a temperature dependant resistor (thermistor). The thermistor is a NTC sensor element. The element resistance decreases as the sensor temperature increases. The ECM supplies the sensor with a 5V reference voltage and a ground and measures the returned signal as a temperature.
The resistance in the sensor changes with intake air temperature. A low intake air temperature will result in a high voltage being returned to the ECM and high intake air temperature will return a low voltage reading of between 0 - 5V.
The ECM monitors the IAT sensor for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system. If the IAT sensor fails, the ECM uses a default temperature value using the fuel rail pressure/temperature sensor.
Knock Sensors
Two knock sensors are located on the front of the engine and are each secured to threaded holes in the engine cylinder block with a bolt. The knock sensors are used by the ECM to monitor combustion knocking or vibration generated by ignition combustion. The knock sensors are each connected to the ECM via a twisted pair of wires which reduces electrical interference disrupting the signal produced.
Each knock sensor contains a piezo-ceramic crystal which produces a voltage when an external force applies pressure or load on it. When the engine is running, compression waves produced by the combustion process, creates pressure waves which pass through the engine cylinder block. These pressure waves are detected by the knock sensors and the deflection of the crystal caused by the pressure waves causes the sensors to produce an output signal. The signals are passed to the ECM which compares them with stored mapped signals in its memory.
The ECM can then determine when the correct combustion occurs in individual cylinders. If incorrect combustion detonation is detected, the ECM can retard the ignition timing on that cylinder for a number of combustion cycles. The ignition timing will be gradually returned to its optimal settings. If the knock is still detected the ECM will increase the injection period, which has a cooling effect on that cylinder.
The signals from the knock sensors are used in conjunction with the CMP sensors and the CKP sensor to determine the ignition cycle and therefore identify which cylinder is knocking. The ECM is programmed to use ignition maps based on high quality 95-98 RON fuel. If fuel of a poor quality such as 91 RON is used the engine may suffer from knock (pinking) for a period of time. The ECM is capable of learning and adapting to the low grade fuel and will modify its internal ignition mapping to compensate for the low grade fuel. This feature of the ECM is called adaption.
If one or both knock sensors fail or the signal becomes implausible, the ECM will cancel closed loop control of the ignition system. The ECM will use a default 'safe' ignition map to ensure the pre-detonation does not damage the engine by setting maximum retard control on spark advance. The driver may notice 'pinking' under certain driving conditions and a loss of performance. The ECM monitors the knock sensors for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system.
Engine Coolant Temperature (ECT) Sensor
The ECT sensor is located in the thermostat housing, on the front of the engine, below the inlet manifold. The ECT sensor is a thermistor type sensor used by the ECM to monitor the engine coolant temperature. The ECM uses the temperature information for the following functions:
^ regulate the injection period
^ set engine idle target speed
^ control the engine cooling fan(s)
^ determine operation of the A/C compressor
^ determine operation of the purge valve and catalytic converter heating function.
The sensor is a Negative Temperature Co-efficient (NTC) thermistor element. The element resistance decreases as the sensor temperature increases. The ECM supplies the sensor with a 5V reference voltage and a ground and measures the returned signal as a temperature.
The ECT sensor is important to the correct running of the engine as a richer mixture is required at low engine coolant temperatures for efficient starting and smooth cold running. As the engine coolant temperature increases, the ECM uses the temperature signal from the sensor to lean off the fuel mixture to maintain optimum emissions and performance.
The ECM monitors the ECT sensor for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system. If the ECT sensor fails, the ECM uses a default value of 90 degrees C (194 degrees F). The electric fan control module is sent a default coolant temperature value of 105 degrees C (221 degrees F) and switches the cooling fan on permanently.
Engine Oil Level/Temperature Sensor
The engine oil level/temperature sensor is located on the underside of the engine and is secured in the engine oil pan with 3 screws and is sealed with an O-ring seal. The ECM supplies the sensor with a 5 V reference voltage and two wires supply the temperature and oil level signals back to the ECM.
Two types of engine oil level/temperature sensor are used. On earlier models a capacitive oil level sensor is fitted and was replaced by an ultrasound level sensor on later models. The principle of the temperature sensor is the same in both sensor types. The sensors can be identified by differences in the sensor housings; the capacitive sensor has the electrical connector moulded square to the base of the sensor, the ultrasonic sensor has the connector moulded at a slight angle to the base of the sensor.
The ECM uses both the oil level and temperature signals to calculate the oil level. Temporary oil level changes caused by hill driving or cornering are taken into account by the ECM using additional information such as vehicle speed and engine load.
Engine Oil Level Sensor - Capacitance Type
The engine oil level sensor comprises two capacitive gauge elements. These measure the resistance to electrical current passing through the engine oil.
There are two capacitors, one measuring the permittivity of the oil and a second with two plates set vertically measuring the height. The second capacitor will have a proportion of oil and air between the plates and since the permittivity of air is different to that of oil, the permittivity reading will change as the level of oil decreases and the air between the plate gap increases. This permittivity reading is compared to that of the oil (taken by the first capacitor) and an oil level is derived.
Engine Oil Level Sensor - Ultrasound Type
The engine oil level sensor uses an ultrasonic pulse, which is reflected back from the surface of the oil. The time it takes for this signal to return to the sensor is turned into a PWM signal and is sent to the ECM. The ECM determines the time taken for the ultrasonic pulse signal to be received and calculates it into an oil level figure.
Engine Oil Temperature Sensor
The engine oil temperature sensor is a Positive Temperature Co-efficient (PTC) thermistor element. The element resistance increases as the sensor temperature decreases. The ECM supplies the sensor with a 5 V reference voltage and a ground and measures the returned signal as a temperature. A low oil temperature will result in a low voltage being returned to the ECM and high oil temperature will return a high voltage reading.
The ECM monitors the engine oil level/temperature sensor for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system. If the sensor fails, the ECM uses the engine coolant temperature sensor signal value as a substitute.
Manifold Absolute Pressure (MAP) Sensor
The MAP sensor is located in the lower part of the intake manifold. The MAP sensor measures the absolute pressure in the intake manifold. The sensor is a semi-conductor type sensor which responds to pressure acting on a membrane within the sensor, altering the output voltage. The sensor receives a 5V reference voltage and a ground from the ECM and returns a signal of between 0.5 - 4.5 V to the ECM. A low pressure returns a low voltage signal to the ECM and a high pressure returns a high voltage.
The MAP sensor detects quick pressure changes in the intake manifold after the electric throttle. The signal is used in conjunction with the MAF sensor signal to calculate the injection period.
The ECM monitors the engine MAP sensor for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system. If the sensor fails, the ECM uses the MAF/IAT sensor signal value as a substitute.
Electric Throttle
The electric throttle is located at the entrance of the intake manifold and is secured to the manifold with four Torx head bolts. The throttle also provides for the connection of the air cleaner housing outlet pipe which is secured to the throttle body with a clip.
The electric throttle comprises the throttle body, a round throttle disc which is actuated by a damper motor and a throttle position sensor. The electric throttle is controlled by the ECM and receives positional signals from the TP sensor. If a failure of the motor occurs, the throttle disc is returned to its closed position by the springs, with limited engine speed available to the driver.
Spindle Damper Motor
The motor is a DC damper motor which drives a gear wheel and two springs; one for opening and one for closing. The motor rotates the spindle to which the throttle disc is attached. PWM signals from the ECM control the damper motor to adjust the position of the throttle disc, regulating the amount of air entering the inlet manifold for combustion.
Movement of the motor is achieved by changing the polarity of the power supply to the DC motor, allowing it to be operated in both directions. The throttle disc and the motor has two maximum positions; throttle disc closed which allows minimal air flow through the electric throttle into the intake manifold and throttle disc open which allows maximum air flow into the intake manifold.
Throttle Position (TP) Sensor
The TP sensor is housed in the electric throttle assembly and is used to check the position of the throttle disc. Two permanent magnets in the sensor connected to the throttle disc affect two Hall effect sensors. As the spindle is rotated the magnets rotate around the Hall effect sensors and produce offset analogue signals back to the ECM. The ECM compares these signals to stored values to ensure that they show an accurate throttle disc position. The offset signals are that one Hall effect sensor produces a higher voltage as the throttle angle increases and the other sensor produces a lower voltage as the throttle angle increases.
The ECM performs a self test and a calibration routine on the throttle disc position at each ignition cycle. This is achieved by the ECM powering the damper motor to fully close the throttle disc and then fully open the throttle disc.
The ECM monitors the DC damper motor and the TP sensor for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system.
Accelerator Pedal Position (APP) Sensor
The APP sensor is located on the accelerator pedal. The sensor comprises a plastic housing which contains two potentiometers and an analogue/digital converter. The potentiometers are connected to a common shaft which is actuated by movement of the accelerator pedal.
The APP sensor provides the ECM and the CJB with information relating to the position of the accelerator pedal. The ECM uses this information to actuate the damper motor in the electric throttle assembly to move the throttle disc to the correct angle in relation to the pedal position.
The APP sensor receives a fused 12 V supply from the CJB, which is controlled by the ignition relay in the BJB. The CJB also provides the sensor with a ground. The sensor provides two outputs; the analogue output is transmitted directly to the CJB, which in turn issues the signal to the ECM on the CAN bus, the second output is the Pulse Width Modulation (PWM) signal which is transmitted directly to the ECM. Both the analogue and PWM signals transmit the same positional information.
The ECM uses the PWM signal to calculate the required position of the electric throttle disc in the electric throttle. In the event of a failure of the PWM signal, the ECM uses the analogue signal received from the CJB as a replacement. If the analogue signal is also incorrect or missing, the ECM limits the maximum engine speed to 2000 rpm.
The PWM and the analogue signal are used for diagnosing faults with the APP sensor. If the ECM detects a difference between the analogue and PWM signals a fault code is stored. The ECM will use the signal with the lowest value for electric throttle control. The APP sensor position and any stored fault codes can be read using a Land Rover approved diagnostic system.