Malfunction Indicator Lamp (MIL)

The malfunction indicator lamp (MIL) is located in the instrument panel cluster. The MIL will display as either SERVICE ENGINE SOON or one of the following symbols when commanded ON:

Fig 1: Identifying MIL Symbol On Instrument Cluster

Courtesy of GENERAL MOTORS CORP.

Fig 2: Identifying Check Engine Light Symbol

Courtesy of GENERAL MOTORS CORP.

The MIL is under the control of the diagnostic executive. The MIL will be turned ON if an emissions-related diagnostic test indicates a malfunction has occurred. It will stay ON until the system or component passes the same test, for 3 consecutive trips, with no emissions related faults.

The MIL indicates that an emissions related fault has occurred and vehicle service is required. The following is a list of the modes of operation for the MIL:

• The MIL illuminates when the ignition is turned ON, with the engine OFF. This is a bulb test to ensure the MIL is able to illuminate.
• The MIL turns OFF after the engine is started if a diagnostic fault is not present.
• The MIL remains illuminated after the engine is started if the control module detects a fault. A diagnostic trouble code (DTC) is stored any time the control module illuminates the MIL due to an emissions related fault.
• The MIL flashes if the control module detects a misfire condition which could damage the catalytic converter.
• When the MIL is illuminated and the engine stalls, the MIL will remain illuminated as long as the ignition is ON.