Computers and Control Systems: Description and Operation

Engine Control System Diagnosis

A warning indicator light is located in the instrument cluster for the engine control system. This light performs three functions.
1. The light will come on if continued engine knocking occurs. This tells the driver to release the accelerator and reduce the engine load so that the knocking will stop.
2. The light will also come on if a fault exists in the system (control unit missing certain inputs or receiving false information). This will usually only occur above 3000 RPM because certain conditions must be met to verify the operation of all components. The light will then go out when engine speed falls below approximately 3000 RPM. The light will stay on as long as engine speed is above 3000 RPM and testing conditions are met if a fault exists in the system.
3. The light also works together with the tachometer for displaying error codes during the diagnosis procedure.