Hello. I have a 2002 F-150 extra cab and have been attempting to wire up a brake controller for my RV. Found the factory installed plug and thought all was good until I read an extra paper that came with the brake controller. Something about Ford adding another wire and not to use the plug as it short out the brake controller. So, found the correct wire that only supplies power when the brake pedal is depressed and spliced in a wire to run connect to the brake controller. As soon as I connected the wire to the controller, the interior lamp relay started clicking and drained power from the truck. Unhooked the cable, charged the battery and all was fine. Just tried to reconnect the wires and controller plug and the relay started clicking like crazy and it drained the battery.

 

I'm not sure what year Ford added the extra wire. I think it coincided with the introduction of the OEM Controller that interfaced with the Truck Modules and the jumper harness the goes between the plug and aftermarket controller made them comparable.

Maybe someone else can weigh in. It's been to long since I used an aftermarket controller for me to remember

 

Quite frankly, I’d grab the jumper harness that’s already made for that controller, plug it in and call it a day.

That is how I did it with the Prodigy in my ‘03.

Some of these get tricky because you can’t just splice like-colored wires and that is likely tripping you up. I’d get pics if I had driven the ‘03 to work today.

Here is Etrailer’s install. Maybe it will help you out. I’ve got a maintenance call to answer on the PA.