Trailer Wiring Module Fault

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Aug 14, 2023 | 08:25 AM

WXboy

Thread Starter

Logistics Pro

Joined: Sep 2002

Posts: 4,411

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From: Central KY

Trailer Wiring Module Fault

Hooked a trailer to the new-to-me '19 F-250 this weekend and none of the lights would work. Got a message on the dash "trailer wiring module fault" and then "left turn signal fault". Checked all the fuses that control trailer lighting. All OK. Pulled apart the 7-pin connector at the bumper and cleaned it well and applied dielectric grease. Reassembled. Now trailer lights and brakes work 90% of the time but occasionally while driving the same error messages pop up, then disappear, then pop up again randomly.

This trailer's lights and brakes work perfectly 100% of the time on my Dad's GMC and my cousin's Ram. So it's not the trailer. Are these Ford trucks that finnicky? What do I need to try next?

Aug 14, 2023 | 09:18 AM

senix

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Joined: Aug 2008

Posts: 37,384

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From: Frederick, MD

does the truck would as it should with other trailers? I would try that next.

Aug 15, 2023 | 09:34 AM

Mike Bartlett

Tuned

Joined: May 2010

Posts: 499

Likes: 132

From: Pleasanton, CA

Try a bigger ground wire from your trailer. You could rig up a temporary from the trailer frame to the truck chassis maybe with jumper cables. I had something similar with my 2019.

Mike

Aug 15, 2023 | 10:12 AM

MAX4utah

Tuned

Joined: Jul 2021

Posts: 424

Likes: 201

My 22’ does this as well. I have not pursued a fix yet. I was going to have the dealer re-flash the brake controller next time I’m there.

Aug 15, 2023 | 12:17 PM

Don Ridley

Fleet Mechanic

Joined: Jan 2023

Posts: 1,339

Likes: 456

Does the trailer have LED lights? There is a setting to switch between standard and LED trailer lights.

Aug 15, 2023 | 01:35 PM