SERVICE ENGINE SOON Warning Indicator
WARNING: This page is about a different car, the 2003 Ford RV Cutaway, 2003 Ford Econoline, 2003 Ford E550 Super Duty, 2003 Ford E450 Super Duty, and 2003 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
The SERVICE ENGINE SOON warning indicator receives its ground from the electronic engine control (EEC) module. The SERVICE ENGINE SOON warning indicator prove-out flashes in the RUN position and is controlled by the EEC.