Malfunction Indicator Lamp: Description and Operation

MALFUNCTION INDICATOR LAMP (MIL)

The MIL notifies the driver 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 (IC) or instrument panel cluster (IPC) and is labeled CHECK ENGINE, SERVICE ENGINE SOON or the international standards organization (ISO) standard engine symbol.
- The MIL is illuminated during the IC (IPC) prove out for approximately 4 seconds.
- The MIL remains illuminated after IC (IPC) prove out if:
- an emission-related concern and DTC exists.
- the PCM does not send a control message to the IC (IPC) (applications with the MIL controlled through the communication link).

- The MIL remains OFF during the IC (IPC) prove out if an indicator or IC (IPC) concern is present.
- To turn OFF the MIL after a repair, a reset command from the scan tool must be sent, or 3 consecutive drive cycles must be completed without a concern.
- For all MIL concerns, go to Symptom Charts. QT: Powertrain Control Module (PCM) Quick Test
- 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 ON engine OFF, unless the OBD inspection/maintenance (I/M) readiness indicators indicate all of the OBD monitors have completed since the last keep alive memory (KAM) reset or since the PCM DTCs have been cleared.