Fuel Filler Cap Loose Warning Indicator (if equipped)
WARNING: This page is about a different car, the 2004 Ford RV Cutaway, 2004 Ford Econoline, 2004 Ford E450 Super Duty, and 2004 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
When the PCM detects that there is a leak in the evaporative emissions (EVAP) system that could be the result of a loose fuel filler cap, the PCM sends a message via the SCP network to the instrument cluster, causing the fuel filler cap loose warning indicator to illuminate.