Hey guys and TY in advance for your help. I visit from time to time but this is my first post looking for help. I apologize for the lengthy post but I want to be specific.
2018 F150 xlt, 5.0, tow package, 60k. I have the integrated trailer brake module. Until 2 weeks ago everything worked 100%. I drove the trailer to the work site and when I leave as soon as I put the truck in Drive (foot on brake) it instantly locks up the trailer brakes 100% . I unplugged everything, turned off the truck, start over and same result. Trailer brakes stayed locked until I unplugged 7pin. Ultimately drove the trailer home unplugged.

The next day I hooked up and plugged into a DIFFERENT trailer with the same result..locked up trailer brake as soon as I put drive. Thus, discerned the issue was in the truck, not the trailer(s).

I visually looked at the truck 7 pin, all looked good. So, purchased a new trailer brake controller Motorcraft part # JL3Z2C006AA. I installed the part. I hooked back up to the trailer and the brakes did NOT lock up as before. All the lights worked but the brakes did not. So, I took it to my ford dealership and had them hook up Forscan reprogram (uninstall/reinstall) the controller thinking it would resolve my issue.

Hooked the trailer up today and the brakes still do not work. I'm at a loss. Just trying to figure out my next move.

many thanks

 

Could be an issue in your harness.
Visually inspect the entire harness where possible and look for any damage. Disconnect, clean terminals, and reconnect everything.
After that, it's gonna be a seek and find with a meter.

 

The dealer shouldn't be using Forscan, they have their own tool for programming. If they did use Forscan, that'd be a red flag for me. The dealer offered no other diagnostic suggestions?

Are there any DTCs set? That may provide a place to start. There's also the Trailer Module located above the brake pedal area - it should be white in color on a black metal bracket. Check there to make sure the connectors are secure and there's no obvious signs of corrosion, etc. That is a programmable module, so it's possible you'd find some DTCs related to that module using Forscan.

 

Can you manually activate the trailer brakes with the slider?

 

NO. When I manually activate the brakes "no trailer attached" message.

I just thought about something else. I recently changed my brake lights and headlights to LEDs. Could that be a possibility? My thought is perhaps they don't draw enough volts to operate the brake controller. (I'm not exactly sure how it works...... Obviously!)

Thank you

 

This is coming from way out in left field, but you don't have the TBC gain set all the way up, do you?

 

No. It doesn't matter where I set it. "No trailer connected" message.

 

The dealer can troubleshoot the issue. Dealers don’t use Forscan, they have Ford’s IDS software and a VCM3 interface to program the truck’s modules. There are steps in the service manual to determine the root cause of the issue. Sounds to me like a problem with the wiring harness or the seven way connector. Check the trailer-related fuses.