Engine Control Module: Description and Operation

The DI System Can Be Divided Into Five Sub-systems.




-The Sensor System sends information to the control system required to achieve optimum control of the ignition.

-The Control System ensures that optimum ignition timing and ignition voltage are obtained for each ignition.

-The High Tension System produces and distributes high tension voltage.

-The On-board Diagnostic (OBD) system has three test functions to facilitate fault tracing. The OBD system works commonly for the fuel system, the TO control system and the DI system.

-The EGR System reduces the emission of nitrogen oxides.

Control Module Monitoring Functions

The control module has a reversible limp-home mode. This means that if a signal returns to a reasonable value after it has been faulty, the control will utilize this value again rather than remaining in limp-home mode.

- If there is no signal from the KS the ignition is retarded approx. 10°.

- If there is no load signal from MFI LH 2.4 or LH 3.1, ignition timing is calculated for full load except when the TP switch indicates that the engine is idling.

-If there is no engine temperature signal, ignition timing is based on the engine being warm.

- If there is no TP signal, the control module takes account of load when the engine is idling.

Ignition Timing Control




The DI control module computes ignition timing twice per revolution, once per ignition. It bases the basic ignition timing on engine speed and the load signal from the MFI control module.

Under certain conditions the control module then adjusts the basic ignition timing to provide for optimum combustion and operation.

- When the car is being started ignition timing is only dependent on engine speed and engine temperature.

- When the engine is idling ignition timing is only dependent on engine speed.

- At temperatures below 55°C (131°F) ignition is retarded as a function of temperature.

- At temperatures below 60°C (140°F) no account is taken of the KS signal.

- If the engine is over-revving the control module uses

the power stage to provide a spark only to every other spark plug so that engine power is reduced.

Ignition Voltage Control

The control module controls the ignition voltage so that it is independent of battery voltage and engine speed. At low voltage the control module sends a signal to the power stage to start charging the coil earlier thereby extending charging time.