Malfunction Indicator Lamp: Description and Operation

The "SERVICE ENGINE SOON" lamp is controlled by the PCM and will turn "ON" for 2 seconds when the engine is turned to the "RUN" position. When the engine is cranked, the lamp will be "OFF". After the key is returned to the "RUN" position, the lamp will turn "ON" for another 2 seconds.

Depending on the trouble code set, the "SERVICE ENGINE SOON" lamp may:

^ Turn "ON" and stay "ON" while the malfunction is taking place. The light will turn "OFF" when the malfunction goes away.

^ Turn "ON" when the malfunction is taking place, and stay "ON" after the malfunction clears. The light will stay "ON" until the ignition key is turned "OFF".