Electronic Control Module/Unit (ECM/ECU)

The ECM controls the delivery of fuel and the timing of ignition spark. It receives information from several different sensors from the vehicle and processes this information to provide optimum performance from the engine. Electrical signals from the fuel and ignition system sensors are received and processed by the electronic circuits in the ECM.

Functions:-

Depending on the vehicle model some or all of the following will be fitted:

Engine coolant temperature (ECT) Sensor

Intake air temperature (AIT) sensor

Throttle Position (TP) sensor

Load sensor volume/mass air flow (VAF/MAF) sensor manifold absolute pressure (MAP)sensor.

Vehicle speed (VSS) sensor.

Crankshaft position (CKP) sensor.

Camshaft position (CMP) sensor

Engine speed (RPM) sensor

Oxygen sensor (O2S)

Knock Sensor (KS)

Barometric pressure (BARO) sensor.

Depending on the vehicle the output from the ECM will control some or all of the following:

Injectors by controlling the length of time each injector valve remains open. Fuel pump relay Idle speed control system. Evaporative emissions system Exhaust gas recirculation system. Ignition timing and knock sensing. Intake manifold length. Self-diagnosis of faults, indicated by an LED on the ECM or a malfunction indicator lamp (mil) or check engine warning light on the instrument panel. Emergency "limp-home" programme, which substitutes an average value for any failed primary sensor enabling the vehicle to be driven to a workshop for correction.