Malfunction Indicator Lamp: Description and Operation

Check Engine Light Operation:

The check engine light is mounted in the instrument cluster. Battery voltage is present at one bulb terminal any time the ignition is turned ON this signal comes from ignition switch terminal Ign. 1. When a system fault is detected, the ECU grounds pin B6 causing the bulb to illuminate. The light is also grounded for two seconds after engine start up to verify the light is functional. The check engine light is used to notify the vehicle operator that service is required.