Malfunction Indicator Lamp (MIL)

The Malfunction Indicator Lamp (MIL) alerts the driver that the Powertrain Control Module (PCM) has detected an OBD II emission-related component or system fault. When this occurs on a California calibrated engine, an OBD II Diagnostic Trouble Code (DTC) will be set. On a federal calibrated engine, certain faults will also turn on the MIL.
^ On all vehicles, the MIL is located on the instrument panel. On F-650/750 and E-Series, it is labeled SERVICE ENGINE SOON. On F-250/550 and Excursion, a symbol is used.
^ Power is supplied to the MIL whenever the ignition switch is in the RUN or START position. If the vehicle is an F-250/550 or Excursion, the indicator is turned on by Standard Corporate Protocol (SCP) communications connected to the instrument cluster. On F-650/750 and E-Series, the indicator is turned on by the PCM.
^ The light may also be on due to a short to ground in the MIL circuit.
^ An engine, with federal calibration, operating in the Failure Mode Effects Management (FMEM) will cause the MIL to be on.
^ To turn off the MIL after a repair, a clear code command from the Scan Tool must be sent.
^ For any MIL concern, go to Symptom Charts.