Pinpoint Test C: The Message Center Displays WIRING FAULT ON TRAILER: Notes
WARNING: This page is about a different car, the 2012 Ford Pickup, 2012 Ford F550 Super Duty, 2012 Ford F450 Super Duty, and 2012 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Refer to OEM WIRING DIAGRAMS - TRAILER & CAMPER ADAPTER -- F250-F550 SUPER DUTY for schematic and connector information.