Malfunction Indicator Lamp: Description and Operation

Malfunction Indicator Light:

PURPOSE
The malfunction indicator light (Check Engine Light) notifies the vehicle operator that an ECM related problem has occurred. The light is also used to extract trouble codes from the ECM.

LOCATION
The light is part of the instrument cluster.

OPERATION
The lamp receives power whenever the ignition is ON. When a fault occurs the ECM grounds terminal W causing the lamp to illuminate. The lamp also is grounded for a few seconds after engine start to verify operation.