Malfunction Indicator Lamp (MIL)

The Malfunction Indicator Lamp (MIL) is located in the instrument panel gauge cluster. The MIL is illuminated by the Powertrain Control Module (PCM) in order to notify the vehicle operator of an engine control system malfunction.

The MIL receives ignition positive voltage anytime the ignition is ON. The PCM illuminates the MIL by providing a ground for the MIL circuit. The MIL should be illuminated whenever the ignition is ON and the engine is not running. Illuminating the MIL whenever the ignition is ON and the engine is not running provides a check of the bulb and circuit. The PCM will turn OFF the MIL once the engine is started or running if there are no engine control system malfunctions.

Many of the conditions for illuminating and extinguishing of the MIL are performed by the PCM in accordance with OBD II regulations. For more information on the MIL function, refer to Powertrain Control Module (PCM) Description (Common OBD II Systems).

The Powertrain On-Board Diagnostic (OBD) System Check guides the user to the correct diagnosis and repair of the MIL circuit.