Engine Control Module (ECM)
ECM monitors and controls vehicle emissions, fuel system, ignition system and other various systems by using input signals from various input devices. ECM processes input signals from input devices and delivers output signals to various components for controlling system operation to achieve optimum engine performance for all operating conditions. See INPUT DEVICES and OUTPUT SIGNALS . ECM contains a fail-safe function which is used in case of sensor or switch failure. Fail-safe function uses preprogrammed values to provide a limp-in mode for minimal driveability. If a failure exists, ECM will inform driver by turning on Malfunction Indicator Light (MIL) on instrument panel. MIL may also be referred to as CHECK ENGINE light.
ECM contains a self-diagnostic system which may store a Diagnostic Trouble Code (DTC) if an electronic control system failure exists. DTC may be retrieved from ECM for system diagnosis using a scan tool. See SELF-DIAGNOSTIC SYSTEM . For ECM location, see Fig 1-Fig 9 .