Electronic Engine Controls - System Operation And Component Description (G1550549): Operation
The ECM (engine control module) processes inputs from the following sources:
- BJB (battery junction box)
- Generator
- CJB (central junction box)
- ECT (engine coolant temperature) sensor
- Immobilizer Antenna Unit (IAU)
- APP (accelerator pedal position) sensor
- Ambient temperature sensor
- LP fuel sensor
- Oil pressure sensor
- CMP (camshaft position) sensor (inlet)
- CMP sensor (exhaust)
- CKP (crankshaft position) sensor
- A/C (air conditioning) pressure sensor
- Pre-catalyst HO2S
- Post catalyst HO2S
- Oil temperature sensor
- FRP
- Turbocharger boost pressure and temperature sensor
- MAP (manifold absolute pressure) sensor
- MAF (mass air flow)
- Knock sensors (2 off)
- Stop lamp switch
- RCM (restraints control module)
- A/C compressor clutch
- Electric throttle position sensors.
The ECM outputs controlling signals to the following sensors and actuators:
- FPDM (fuel pump driver module)
- Cooling fan control module
- Fuel injectors
- Fuel metering valve
- Turbine by-pass control actuator valve
- VCT (variable camshaft timing) solenoid (inlet)
- VCT solenoid (exhaust)
- Purge valve
- Ignition coils (4 off)
- Electric throttle motor
- DMTL pump (NAS only).
The ECM is connected to the engine sensors which allow it to monitor the engine operating conditions. The ECM processes these signals and decides the actions necessary to maintain optimum engine performance in terms of drivability, fuel efficiency and exhaust emissions. The memory of the ECM is programmed with instructions for how to control the engine, this known as the strategy. The memory also contains data in the form of maps which the ECM uses as a basis for fueling and emission control. By comparing the information from the sensors to the data in the maps, the ECM is able to calculate the various output requirements.
The ECM contains an adaptive strategy which updates the system when components vary due to production tolerances or ageing. Some sensors receive a regulated 5 Volt supply from the ECM.
The ECM receives a vehicle speed signal on a CAN (controller area network) bus from the ABS (anti-lock brake system) module. Vehicle speed is an important input to the ECM strategies. The ABS derives the speed signal from the ABS wheel speed sensors. The frequency of this signal changes according to road speed. The ECM uses this signal to determine the following:
- How much to reduce engine torque during gear changes
- When to permit speed control operation
- To control the operation of the speed control system
- Implementation of the idle strategy when the vehicle is stationary.
Ignition is controlled by a direct ignition system, provided by 4 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 controls operation of the starter motor via the starter relay in the BJB. The ECM also protects the starter motor, preventing operation of the starter relay if the engine speed signal exceeds a predetermined value
The ECM and the CJB exchange encrypted data to validate and approve an engine start. For additional information, refer to: Anti-Theft - Passive (Description and Operation),