Malfunction Indicator Lamp: Description and Operation

DESCRIPTION

The Malfunction Indicator Lamp (MIL), is used to inform the driver when the system detects a malfunction in a monitored device or circuit. It can also be used to display trouble codes to assist technicians in diagnosing problems with computer controlled systems and devices. This light, located in the instrument panel has been called by other names including Service Engine Soon (SES) light, and Check Engine Light (CEL).

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. 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 MIL. See TROUBLE CODE DESCRIPTION under DIAGNOSIS, TESTING AND INSPECTION PROCEDURES/TESTING PROCEDURES.