Malfunction Indicator Light (MIL)

The MIL may also be referred to as the CHECK ENGINE light. When ignition is first turned on, MIL should come on for approximately 5 seconds to verify bulb and circuit operation, and then go off. The MIL is located on instrument panel, to the left of the tachometer.

The Engine Control Module (ECM) monitors several different engine control system circuits. If malfunction occurs which affects vehicle emissions, a Diagnostic Trouble Code (DTC) will be stored in ECM. When DTC is stored in ECM, the ECM will turn on the MIL the next time the ignition is turned on and the same malfunction exists on all malfunctions except for excessive time to enter closed loop. If an excessive time to enter closed loop condition exists, the MIL will be turned on when the first detection of the malfunction exists. The MIL will remain on steady until DTC is cleared from the ECM. If any other DTC exists that does not affect vehicle emissions, the MIL will not be turned on.

If MIL fails to come on with ignition is first turned on, or remains on steady with no DTCs stored in ECM, proceed to TROUBLE SYMPTOMS for diagnosis of the MIL. TROUBLE SYMPTOMS are listed after the Diagnostic Trouble Code (DTC) tests in SELF-DIAGNOSTIC SYSTEM section in this article.

The ECM will turn off MIL when malfunction is not detected during 3 consecutive engine start-to-stop trips on all applications except an engine misfire or fuel trim malfunction. On engine misfire or fuel trim malfunction, ECM will turn off MIL when malfunction is not detected when condition such as engine speed, engine coolant temperature etc. are similar to those when malfunction was first recorded.