Somerset Regal L4-151 2.5L (1985)
Malfunction Indicator Lamp: Description and Operation
The SERVICE ENGINE SOON indicator glow when there is a problem or malfunction in the engine. Voltage from the gauges fuse flows to the bulb in
RUN, BULB TEST< or START. If the ECM detects a problem in the engine, it supplies a path to ground for the bulb.
