SFI Engine Management System

Description
The engine management system (EMS) maintains optimum engine performance over the entire operating range. The correct amount of fuel is metered into each cylinder inlet tract and the ignition timing is adjusted at each spark plug.

The system is controlled by the ENGINE CONTROL MODULE (ECM) which receives data from sensors located on and around the engine. From this information it provides the correct fuel requirements and ignition timing at all engine loads and speeds.

The fuel injection system uses a hot wire Mass Air Flow Sensor to calculate the amount of air flowing into the engine.

The ignition system does not use a distributor. It is a direct ignition system (DIS), using four double ended coils. The circuit to each coil is completed by switching inside the ECM.

The on board diagnostic system detects any faults which may occur within the EMS. Fault diagnosis includes failure of all EMS sensors and actuator's, emissions related items, fuel supply and exhaust systems.

The system incorporates certain default strategies to enable the vehicle to be driven in case of sensor failure. This may mean that a fault is not detected by the driver. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.

A further feature of the system is 'robust immobilisation'.

Crankshaft position sensor (CKP Sensor)
The crankshaft position sensor is the most important sensor on the engine. It is located in the left hand side of the flywheel housing and uses a different thickness of spacer for manual and automatic gearboxes. The signal it produces informs the ECM:
- the engine is turning
- how fast the engine is turning
- which stage the engine is at in the cycle.

As there is no default strategy, failure of the crankshaft sensor will result in the engine failing to start. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.

Camshaft position sensor (CMP Sensor)
The camshaft position sensor is located in the engine front cover. It produces one pulse every two revolutions. The signal is used in two areas, injector timing corrections for fully sequential fuelling and active knock control.

If the camshaft sensor fails, default operation is to continue normal ignition timing. The fuel injectors will be actuated sequentially, timing the injection with respect to top dead centre. Injection will either be correct or one revolution out of synchronisation. The fault is not easily detected by the driver. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.

Mass air flow sensor (MAF Sensor)
The 'hot wire' type mass air flow sensor is mounted rigidly to the air filter and connected by flexible hose to the plenum chamber inlet. The sensing element of the MAP Sensor is a hot wire anenometer consisting of two wires, a sensing wire which is heated and a compensating wire which is not heated. Air flows across the wires cooling the heated one, changing its resistance. The ECM measures this change in resistance and calculates the amount of air flowing into the engine.

As there is no default strategy, failure will result in the engine starting, and dying when it reaches 550 rev/min, when the ECM detects no MAP Sensor signal. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.