System Description

System Schematic:

PURPOSE
The ECM and sensor and output systems control virtually all aspects of engine operation. This combined control allows the engine to function at optimum performance while maintaining acceptable emission and fuel economy levels.

OPERATION
During normal vehicle operation, the ECM controls fuel, spark and emission systems. In the event of a sensor failure or inconsistency, the unit switches to "Fail-Safe" mode. In this mode, certain sensor and output parameters become "fixed," allowing limited vehicle operation. In most cases, the "Check Engine" lamp is illuminated and trouble codes are recorded in ECM long term memory. These alert the operator that a system requires attention and guides the technician toward the failed system.