Part 4

Electronic Engine Controls

Air Conditioning (A/C) Relay
The A/C relay is located in the BJB. The operation of the A/C relay is controlled by the ECM which provides a ground path for the A/C relay coil, energizing the relay and closing the relay contacts.
When the relay contacts are closed, battery voltage is supplied via the relay to the A/C compressor clutch. The ECM controls the operation of the variable displacement compressor using a signal line to the compressor and received signals from the A/C pressure sensor.

Air Conditioning Compressor Control
Compressor displacement is controlled by the ECM based on current evaporator temperature and target evaporator temperature signals received from the ATC module. From these values the ECM calculates the required compressor displacement and provides a Pulse Width Modulated (PWM) signal to the compressor solenoid valve. The compressor solenoid valve is mounted on the rear of the compressor and interprets the PWM signal as a displacement value and alters the position of the internal swash plate accordingly.
The ECM will also reduce the displacement of the A/C compressor to its minimum level if 'full throttle' or automatic transmission 'kick down' is requested. This feature is not present on Gulf specification vehicles. Compressor clutch engagement is controlled by the ECM.

Engine Cooling Fan Control
The ECM has a hardwired connection with the cooling fan control module. The ECM outputs a PWM signal to the fan control module which relates to the required fan speed. The fan speed is determined by factors such as engine coolant temperature and A/C operation. The fan control module reacts to the received signal by controlling the operating voltage of the fan motors. The fan control module confirms the fan speed operation on the same connection back to the ECM.

Starter Motor Relay
The starter motor relay is located in the BJB. The operation of the starter motor relay is controlled by the ECM which provides a ground path for the relay coil, energizing the relay and closing the relay contacts. When the relay contacts are closed, battery voltage is supplied, via the starter motor relay, to the starter module solenoid coil. The starter solenoid is energized and connects the starter motor with a direct battery feed to operate the starter motor.
Once the engine has started, the ECM removes the starter motor relay ground, opening the relay contacts and terminating the battery feed to the starter solenoid, which in turn stops the operation of the starter motor. For additional information, refer to Starting System - 3.2L Description and Operation

Fuel Pump Module
The fuel pump is controlled by the FPDM which in turn is controlled by the ECM. The FPDM provides positive and negative feeds to the fuel pump motor which is controlled with a PWM output. The fuel pump is run for 2 seconds to prime the fuel system once ignition on is sensed by the ECM.For additional information, refer to Fuel Tank and Lines Fuel Tank and Lines

Malfunction Indicator Lamp (MIL)
The MIL is located in the instrument cluster and is illuminated by a CAN message from the ECM when an emission related fault occurs. The ECM also illuminates the MIL when requested to do so by the TCM and to perform a bulb check when the ignition is switched on. There is no MIL illumination for non emission related engine management faults. All engine faults are recorded with a Diagnostic Trouble Code (DTC) which can be retrieved using a Land Rover approved diagnostic system. For additional information, refer to Electronic Engine Controls - 3.2L Testing and Inspection

Generator Feedback Signal
The generator has a Local Interconnect Network (LIN) bus connection direct to the ECM. The LIN bus is used by the ECM to request voltage for battery charging and to monitor the fault status of the generator.

PRINCIPLES OF OPERATION

Starting Process
The ECM will only allow engine crank, spark and injector functions when the following conditions are met:
- A hardwired Park/Neutral signal is received from the Transmission Control Module (TCM)
- A hardwired ignition signal is received from the CJB
- A hardwired crank request signal is received from the CJB
- Encrypted data exchange between the instrument cluster and the ECM is verified.
Before the CJB will send the hardwired ignition signal, it must satisfactorily complete the following:
- Exchange encrypted data with the start control module to validate the remote handset.
Additionally, before the CJB will send the hardwired crank request signal it must receive the following signals:
- Brake signal from the speed control inhibit switch
- Hardwired transmission in Park (P) or Neutral (N) signal from the selector lever assembly.
With the remote handset inserted in the start control module and the stop/start button is pressed, the start control module issues battery voltage high signal on the LIN bus connection to the CJB and the fuel pump is run for 2 seconds to prime the fuel system. The CJB uses this signal together with the stop lamp switch signal and issues a crank request message on the high speed CAN bus to the ECM.
The ECM, on receipt of the crank request message, then provides a power and ground supply to the starter relay in the BJB, closing the relay contacts. Battery voltage is supplied via a fuse through the starter relay and is passed to the starter motor solenoid coil. The coil is energized, closing the solenoid contacts and allowing a fuse battery voltage supply direct from the battery to operate the starter motor and crank the engine and simultaneously switch the fuel pump on.
The ECM operates the starter motor until the engine starts which is determined by the engine speed exceeding a pre-determined value.

Auto Start
The ECM has an auto start function which allows the engine to continue cranking if the stop/start button is released. The starter motor will operate until the engine starts or a pre-determined period of time has elapsed which is based on engine coolant temperature. Low engine coolant temperatures allow longer crank times. If the engine does not rotate or the engine speed is low, the ECM removes the power supply and ground from the starter relay stopping the crank process.

Start Prevention
Operation of the starter motor will not be allowed or will be interrupted if:
- the engine is running and the engine speed has exceeded a predetermined speed
- the encrypted data exchange between the instrument cluster, ECM, CJB and start control module has failed to identify the remote handset
- the gear selector lever is not in the park 'P' or neutral 'N' position. The signal is determined from a signal from the TCM and also the transmission mounted position switch
- the brake pedal is not pressed.

Engine Stop Process
To stop the engine the stop/start button must be pressed. Forcibly removing the remote handset from the start control module will not stop the engine. On models with automatic transmission, once the engine has stopped the remote handset will not be released by the start control module until the transmission selector lever is in the Park (P) position.

Throttle Control
The ECM controls the positioning of the throttle disc in the electric throttle using information from the APP sensor and the TP sensor. Data from the A/C pressure sensor, TCM, ECT sensor, MAF sensor and the MAP/IAT sensor is also used to determine the correct throttle control.
The two Hall effect sensors in the TP sensor are designated 1 and 2. Both sensors output an increasing voltage as the throttle disc angle increases. Small air flows through the throttle require comprehensive regulation, therefore the voltage rise in one of the sensors increases more quickly than the other sensor which gives accurate control of the throttle and ensure the throttle disc is in the correct position.
The ECM monitors the signals from both sensors to ensure they are within the minimum and maximum thresholds and that the signals correspond to the same throttle disc position. If there is a difference in the signals the ECM uses a default throttle signal calculated from the electric throttle load, engine speed and air pressure and temperature signals. The sensor whose output signal is closest to the calculated throttle disc angle will be used as the correct output. A fault code will be recorded for the other sensor and this can be read using a Land Rover approved diagnostic system. The ECM then monitors the remaining sensor output signal and compares it against the calculated value. If a difference in the comparison occurs the ECM will discount the output from both sensors and disable the electric throttle control and revert to a limp home mode. The throttle disc has springs for opening and closing and the ECM can measure the load applied by these springs for a load
signal. If a fault occurs which prevents the damper motor from being operated, the springs return the throttle disc to a position which allows a throttle opening large enough to allow the vehicle to driven, but with reduced drive ability.

Throttle Adaptations
The ECM has a learning adaption which allows the ECM to calculate the precise control required for the electric throttle damper motor. The adaption process is performed when the ignition is on and the engine is not running. The throttle disc is moved by the damper motor to the fully closed position and the ECM records the values output by the TP sensor potentiometers.
If the permanent battery supply to the ECM has been removed, then previous adaptations will have been lost. If adaptations are stored, then the ECM compares the stored adaption values with the current throttle angle and uses an average of the stored and current values to create the new adaption value.
If the electric throttle unit has been replaced, the power supply must be removed from the ECM to erase all previously stored adaption values.

Fuel Pressure Regulation
Fuel pressure regulation is controlled by the ECM to respond to fuel pressure demand and provides stepless control of the pump output using the FPDM to control the pump operation. The ECM can vary the fuel pressure to between 55.1 lbf/in2 (3.8 bar) and 72.5 lbf/in2 (5 bar). The high pressure is only used in extreme conditions such as heavy engine loads and engine starts.
The ECM uses the signals from the fuel rail pressure/temperature sensor to determine information regarding the pressure and temperature of the fuel and provide precise injection periods, improving engine starting under all conditions. The advantage of controlling the fuel pump output pressure are that pump power consumption is reduced, lowering the load on the power supply system and reducing fuel consumption, improved service life of the pump and reduced fuel pump noise.

NOTE:
When the ignition is switched off the FPDM reduces the fuel line pressure regulation to 29 lbf/in2 (2 bar) to help reduce injector leakage.


Knock Control
Knock occurs in a cylinder when the fuel and air self ignites at the wrong timing. This can occur either before or after the spark is produced. The fuel mixture can ignite in different areas of the combustion chamber and results in a fast combustion process creating several separate fuel combustions which together combine to produce a mechanical knocking sound. The sounds produce a certain type of vibration through the engine cylinder block and these are detected by the knock sensors. The two knock sensors detect knocks on cylinders 1, 2 and 3 and 4, 5 and 6 respectively.
The vibrations act upon the peizo crystals within the sensors which results in a voltage being produced which is sensed by the ECM. The ECM, using the CMP sensors and the CKP sensor, can determine which cylinder(s) are knocking. The ECM is able to filter the signal to detect vibrations created during normal engine operation and discard them from the knock detection. The ignition timing is gradually advanced until the knocking is detected once again.
Once the ECM has determined knocking is occurring using other inputs such as catalytic converter temperature for example in addition to the signals from the knock sensors, it first retards the ignition timing and subsequently richens the air/fuel if required.

Variable Camshaft Timing (VCT) Control
The inlet camshaft is controlled by the ECM using the VCT solenoid. The exhaust camshaft is fixed and its timing cannot be changed.
Both camshafts are driven indirectly from the crankshaft via a chain. The chain is driven from a shaft in the gear housing assembly. For additional information, refer to Engine - 3.2L The VCT allows the ECM to adjust the inlet camshaft position in relation to the crankshaft, altering the timing of the opening and closing of the inlet and exhaust valves relative to the crankshaft position. This allows the ECM to provide increased engine performance, improved idle quality and reduced emissions.
The position of the inlet camshaft is determined by the ECM using signals from the CKP sensor and the CMP sensors. The ECM can then use the VCT solenoid valve to control the angle of the camshaft by controlling the flow of oil to the VCT unit.
The camshaft is secured to the rotor in the VCT unit. Oil pressure supplied to either side of the VCT unit from the VCT solenoid valve can rotate the rotor and hence the camshaft in either direction. The VCT solenoid is operated by the ECM using PWM, high frequency switching which provides rapid and precise control of the inlet camshaft position. The inlet camshaft position can be adjusted within 40 degrees of crankshaft rotation.

Camshaft Profile Switching (CPS) Control
The inlet camshaft has, in addition to the VCT control, a CPS function which is also controlled by the ECM. The CPS control can vary the valve lift height and duration of the camshaft lobes by adjusting the area of the hydraulic tappet which acts on one of two cam lobe profiles. The CPS control is via two CPS solenoid valves, located at each end of the inlet camshaft. The CPS solenoid valves control the position of hydraulic tappet assemblies which can be set in one of two positions; low and high.
Two CPS solenoids are used so that the hydraulic tappets can be adjusted when no load is applied, for example the cam lobes are off the hydraulic tappets and the cam base circle is acting on the tappet, this keeps the stress on components to a minimum. One CPS solenoid supplies oil pressure to the hydraulic tappets of cylinders 1, 2 and 4 and the second CPS solenoid supplies oil pressure to the tappets of cylinders 3, 5 and 6.
At engine start and at low engine oil temperatures (below 40°C (104°F)) the ECM does not direct engine oil pressure to the hydraulic tappets and therefore the hydraulic tappets are in their spring loaded, low position. For additional information, refer to Engine - 3.2L

Ignition Control
The ECM calculates the optimum ignition timing based on pre-programmed maps and information from the following sensors:
- CKP sensor
- CMP sensors
- MAF sensor
- ECT sensor
- Electric throttle TP sensor
- Knock sensors
- TCM
- Ignition coils.
During engine starting the ECM uses a fixed ignition setting. When the engine has started and the vehicle is being driven, the ECM adjusts the ignition timing accordingly using other parameters such as engine speed, load and temperature.
Once the engine has reached its normal operating temperature, the ECM monitors the signals from the knock sensors. If any of the cylinders produce knocking, the ignition timing for that cylinder will be retarded until the knocking has stopped. The ignition is then gradually advanced back to the normal timing or until the knocking re-occurs.
The ECM uses information from the TCM to provide torque limitation during transmission shifts. The ignition timing is adjusted to momentarily reduce the engine torque output to give a smooth transmission shift and reduce load on the transmission.

Air Conditioning (A/C) Compressor Control
The ECM controls the operation of the A/C compressor and reacts to requests from the ATC module via the high speed CAN bus. The compressor is a variable displacement unit and the ECM controls, via a solenoid, the displacement of the compressor to adjust load during certain driving conditions.
During engine start-up, moving from a standstill and under hard acceleration, the ECM sets the minimum displacement of the compressor to reduce the effect on the engine torque output. The ECM uses information from the ATC module, the A/C pressure sensor, the electric throttle TP sensor and the ECT sensor to determine compressor control. The ATC module transmits climate control and driver requests to the ECM and the ECM determines the priority of these requests over engine performance.