Trailer Wiring Fault

[Muddy Bean]

Plugged a trailer with brakes into my truck last week. Truck pretended there isn’t a trailer but when I squeezed the controller I did indeed have brakes. Turn signals, brake lights, running lights all worked on trailer and truck without issue. Unhooked that day and ever since I’ve had the dreaded “Trailer Wiring Fault” message come up every time I start the truck. Went to tow again yesterday and as soon as you plug the trailer in, it engages the trailer brakes and you can’t move. I had to drive yesterday without the trailer plugged in...no lights, nothing. Checked every single fuse related to the trailer both under hood and in kick panel. All are good. Please someone give me the next step here. I know for a fact this isn’t a problem with the trailer as we are towing it with another Ford truck and not having any issues at all with it.

2015 Expedition EL with heavy duty tow package.


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[HawkX66]

Plugged a trailer with brakes into my truck last week. Truck pretended there isn’t a trailer but when I squeezed the controller I did indeed have brakes. Turn signals, brake lights, running lights all worked on trailer and truck without issue. Unhooked that day and ever since I’ve had the dreaded “Trailer Wiring Fault” message come up every time I start the truck. Went to tow again yesterday and as soon as you plug the trailer in, it engages the trailer brakes and you can’t move. I had to drive yesterday without the trailer plugged in...no lights, nothing. Checked every single fuse related to the trailer both under hood and in kick panel. All are good. Please someone give me the next step here. I know for a fact this isn’t a problem with the trailer as we are towing it with another Ford truck and not having any issues at all with it.

2015 Expedition EL with heavy duty tow package.


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Start with ground IMO. Hook up the trailer and see how the ground between the two is. Better yet, hook up a temp ground and see if there's any difference. I have the electrical diagrams if you need something in particular. I'm not sure how the truck "senses" the trailer. Mine does the same thing. 17 Plati. Probably voltage drop or something.

 

[Muddy Bean]

Thanks Hawk,

From my research on the f150 forums and other places, this isn’t a wiring issue. It happens even when no trailer is attached. It has happened to people who have never hooked to a trailer and had only 1500 miles on their trucks. It appears to be a bad brake controller module and when I unplug it the brakes on the trailer release and I can tow and have lights but just no brakes. So I’m going to just replace the module


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[HawkX66]

That makes sense and sounds a whole lot easier. Good luck!

 

[99WhiteC5Coupe]

Plugged a trailer with brakes into my truck last week. Truck pretended there isn’t a trailer but when I squeezed the controller I did indeed have brakes. Turn signals, brake lights, running lights all worked on trailer and truck without issue. Unhooked that day and ever since I’ve had the dreaded “Trailer Wiring Fault” message come up every time I start the truck. Went to tow again yesterday and as soon as you plug the trailer in, it engages the trailer brakes and you can’t move. I had to drive yesterday without the trailer plugged in...no lights, nothing. Checked every single fuse related to the trailer both under hood and in kick panel. All are good. Please someone give me the next step here. I know for a fact this isn’t a problem with the trailer as we are towing it with another Ford truck and not having any issues at all with it.

2015 Expedition EL with heavy duty tow package.


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I bought a new 2015 Ford Expedition Limited 4x4 with the HD tow package. It has never been wrecked or damaged.

I have never towed with it or connected a trailer, or opened the 4 or 7 pin connector covers.

Since new, the truck will randomly display the “trailer wiring fault” message on the DIC. At times, after starting the engine with the push button start, it will also display “no key detected”.

I have returned it to the selling dealer several times, including providing a picture of the message. Each time, the dealer said there were no codes, thus nothing to repair. I have stopped going to this dealer due to their poor service.

The defect has annoyed me and clearly Ford has no idea how to fix it, or their dealers would have a TSB to refer to.

I don’t want to just start replacing parts, and the dealer was no help. I hope someone has a solution to this problem.

 

[Eagle 71]

So I’m going to just replace the module

Muddy, please post results of swapping out the module.
Assuming you purchased the new module thru a Ford dealership, will they accept the return of the new module if (after running trons thru it), it doesn't solve your problem? Bottom line though, hope it does.

 

[Muddy Bean]

I’ll let you all know. I have no idea if ford would take a return. If I found a really kind dealer then maybe... I’m pretty sure this is the issue though.


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[cmiles97]

Based upon the F150 forums with this issue, I went after market for my brake controller. It's ugly as it is down below the dash but the system still sees the trailer and I can use the trailer sway control. I've had it a year and 20K miles, not one "trailer wiring fault". PS I towed my utility trailer last weekend to take my motorcycle out of it at the apartment complex. Even drove a few extra miles to make sure the trailer was ok after sitting outside at a storage place. Everything worked perfect. The ford system saw it as soon as it was plugged in as the trailer I setup in the software.

 

[Muddy Bean]

Based upon the F150 forums with this issue, I went after market for my brake controller. It's ugly as it is down below the dash but the system still sees the trailer and I can use the trailer sway control. I've had it a year and 20K miles, not one "trailer wiring fault". PS I towed my utility trailer last weekend to take my motorcycle out of it at the apartment complex. Even drove a few extra miles to make sure the trailer was ok after sitting outside at a storage place. Everything worked perfect. The ford system saw it as soon as it was plugged in as the trailer I setup in the software.

Which one are you using? I’m interested as I think this will continue to happen even with new ford brake controllers.


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[cmiles97]

Which one are you using? I’m interested as I think this will continue to happen even with new ford brake controllers.


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Tekonsha 9330 Voyager Electronic. The installer ran all new wire back and installed a 7pin connector. I'm not sure how he integrated it into the ford system, I'll assume they have a pre-made cable with quick connect that does that.

https://www.amazon.com/Tekonsha-903...ocphy=9004728&hvtargid=pla-449393663642&psc=1