Computerized Engine Controls: Notes

Computerized engine control system consists of various input devices which detect vehicle operating conditions. Electronic Control Module (ECM) monitors input signals received from input devices and sends output signals to control air/fuel mixture, idle air system, spark advance, fuel pump operation And EGR operation (if equipped). This lowers exhaust emissions, while maintaining fuel economy and driveability.

ECM has self-diagnostic capabilities, built-in fail-safe mechanism and back-up power. If an engine control system fault occurs, ECM activates CHECK ENGINE light and stores trouble codes in ECM memory for diagnostic purposes. Fail-safe mechanism substitutes preprogrammed sensor values to the ECM if a sensor fails, thus providing a certain level of engine performance.