Principles of Operation

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.

The trailer lamps and trailer battery charge are supplied power by relays that are energized to correspond with the exterior lighting and ignition state functions of the vehicle.

If the vehicle is not equipped with the factory manufactured Trailer Brake Control (TBC) module, the vehicle supplies circuitry to support the installation of an aftermarket TBC module (installed by the customer). To support the aftermarket TBC module, the vehicle circuitry only supplies voltage, ground, stoplamp switch input and a brake controlling circuit to the trailer tow connector. The trailer electric brakes themselves are controlled by the aftermarket trailer brake controller and not the vehicle itself.

For diagnostics and a description of the factory manufactured trailer brake control system, refer to AUXILIARY BRAKE SYSTEM -- F250-F550 SUPER DUTY .