Indicator Lamps

The SERVICE ENGINE SOON indicator lamp is pulled to by the powertrain control module (PCM). When the lamp is pulled to ground, current from the ignition circuit flows through the indicator lamp, allowing it to illuminate. This indicates to the vehicle's operator that there is a possible problem with the engine control system.

During engine start-up the SERVICE ENGINE SOON indicator lamp is illuminated, for approximately two seconds, by the PCM for a bulb check.