Trailer Wiring Fault message

[Joey Smith]

I have a 2019 Expedition XLT Max 4x4 with heavy tow package.

When going on a trip with my trailer, I saw Trailer Wiring Fault 2-3 times upon hooking up and moving forward. I would drive it forward to a safe spot. During that time everything seemed to work ok (brakes). I would go and re-seat the 7 pin connector and restart the car and the message would be gone.

Anyone else have this happen?

I brought it in to the Ford dealership and they said they don’t have a trailer and that it was probably a problem with the trailer. I asked them to run diagnostics anyways and see if there are any issues.

I suspect they will say they do no see anything.

Am interested if others have seen this and have found ways to resolve it. Did it end up being a trailer wiring issue?

Thx!


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[flying68]

First reaction is most likely a trailer or trailer connector issue. Could be as simple as a bad ground connection (corroded or loose).

 

[Boostedbus]

I have seen this intermittently pop up on the screen on my 2017 Expedition (trailer is disconnected) and it was a faulty ground. You can run a second remote ground wire from the trailer frame to the truck hitch frame and that should most likely stop the problem. Make sure you scratch/grind the paint off to bare metal on both connections, drill 1/8 inch hole, apply some dielectric grease, and screw in a self tapping screws to fasten loop wire connector ends. You can also put an easy pull apart disconnect link in between on the wire.

 

[99WhiteC5Coupe]

I ordered and bought a new 2015 Ford Expedition Limited 4x4 with the HD tow package.

Since new, the vehicle intermittently displays “trailer wiring fault” messages. There is no pattern to the messages being displayed. At times, it will display the trailer message AND “no key detected” (after the vehicle is started with the push-button start).

I have never towed or hooked up a wiring harness to the four or seven pin factory connectors.

I returned the vehicle to the dealer and was told “no codes stored”.

The messages continued, so I took a photo of the message and returned to the dealer. Since the vehicle was not displaying the message when I arrived (although I had a photo) - the dealer said there was nothing they could do.

Others on this forum have posted that they fixed the problem by replacing the factory trailer brake controller.

 

[Joey Smith]

As I expected, the Ford service people said they could not find anything.

I will try and take a closer look at the trailer cord/connector and see if it is corroded. I just got the trailer (2017, used) and am still figuring things out. I had read I should be using some contact cleaner to keep the electrical connections clean. The WD40 Contact Cleaner just arrived so I plan to see if that does anything first before doing anything else.

Thx for the responses.


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[gaspass]

Any progress on this issue? I had a similar issue in that if the headlights were turned on I got a trailer disconnected alert as well as turn signal faults every time I hit the brakes. If the lights were not turned on then there was no alerts. Throughout all of this the lights(turn, stop and running) all functioned appropriately.
I am thinking a short somewhere but sure where to start. Another posting suggested looking at the wiring between the 7-pin and 4-pin connectors

 

[Yupster Dog]

I am thinking a short somewhere but sure where to start.

If your problem is trailer light wiring/truck plug wiring,
They sell trailer light testers and they are not expensive. Get the one you put between the trailer lights and your truck plug. It will tell you which direction and what wire to fix.