Malfunction Indicator Lamp: Description and Operation

DESCRIPTION
The Malfunction Indicator Light (MIL, also referred to as the Service Engine Soon - SES light) is used to inform the driver when the system detects a malfunction in a monitored device or circuit. It can also be used for displaying trouble codes to assist diagnosing fuel injection problems.

OPERATION
The MIL should be lit when the ignition is turned "ON", and go out after the engine starts. If the light does not go out after starting the engine, a problem has been detected that affects emissions &/or driveability, and one or more trouble codes are stored in memory. If this is the case, the vehicle should be serviced.

NOTE: Not all malfunctions will set trouble codes. Also, some codes may be present in computer memory and not light the SES light. See TROUBLE CODE DESCRIPTION under DIAGNOSIS, TESTING AND INSPECTION PROCEDURES/TESTING PROCEDURES.