The malfunction indicator lamp (MIL) is located on the instrument panel. The lamp is labeled -Check Engine- on 1993-97 vehicles, and -Service Engine Soon- on 1998-00 vehicles. The lamp is connected to the PCM, and will alert the driver to certain malfunctions within the electronic engine control system. When the lamp is illuminated, the PCM has detected a fault and stored a DTC in the memory.
The light will stay illuminated as long as the fault is present. Should the fault self-correct, the MIL will extinguish, but the stored code will remain in the memory.
Under normal operating conditions, the MIL should illuminate briefly when the ignition key is turned ON . This is an MIL circuit check to verify that the lamp operates. If the lamp does not light, the bulb and/or circuit should be repaired. As soon as the PCM receives a signal that the engine is cranking, the lamp should extinguish. The lamp should remain extinguished during the normal operating cycle.
The MIL may also be used for retrieving DTCs when the PCM is put in diagnostic mode. When in diagnostic mode, the MIL will emit a series of flashes, indicating which DTCs are stored in the PCM memory.