Malfunction Indicator Lamp: Description and Operation

Malfunction Indicator Lamp (MIL)

The MIL notifies the driver that the powertrain control module (PCM) has detected an on board diagnostic (OBD) emission-related component or system concern. When this occurs, an OBD diagnostic trouble code (DTC) sets.

- The MIL is located in the instrument cluster and is labeled CHECK ENGINE, SERVICE ENGINE SOON or the international standards organization (ISO) standard engine symbol.

- The MIL is illuminated during the instrument cluster prove out for approximately four seconds.

- The MIL remains illuminated after instrument cluster prove out if:

- an emission-related concern and DTC exists.

- the PCM does not send a control message to the instrument cluster (applications with the MIL controlled through the communication link).

- the PCM is operating in the hardware limited operation strategy (HLOS).

- The MIL remains off during the instrument cluster prove out if an indicator or instrument cluster concern is present.

- To turn off the MIL after a repair, a reset command from the scan tool must be sent, or three consecutive drive cycles must be completed without a concern.

- For all MIL concerns, go to Symptom Charts No Diagnostic Trouble Codes (DTCs) Present Symptom Chart Index.

- If the MIL flashes at a steady rate, a severe misfire condition may exist.

- If the MIL flashes erratically, the PCM can reset while cranking if the battery voltage is low.

- The MIL flashes after a period of time with the ignition in the RUN position (engine not running) if DTC P1000 is set.




CHECK ENGINE, SERVICE ENGINE SOON, or ISO Standard Engine Symbol