"Service Engine Soon" Light

A malfunction of control module, wiring harness or solenoid(s) will cause an amber "SERVICE ENGINE SOON" instrument panel light to illuminate. With ignition switch "ON" and engine not running, "CHECK ENGINE SOON" light will be "ON". This is used as a bulb check (except 7.4L models). When engine is started, light will remain on for 3-6 seconds and then turn off.

On 7.4L system, with ignition "ON" and engine not running, "SERVICE ENGINE SOON" light will come "ON" and stay "ON" for 1-2 seconds and then go "OFF". This is also a bulb check.