Hi everyone,
We purchased a 2021 F-150 3.5L ecoboost and when we connected it to our travel trailer, everything seemed fine. 10 minutes down the road we got a message on the dash "Trailer Light Module Fault" - the brakes, left/right signal and 4 ways weren't working, but the night lights on the trailer were still on. Has anyone else experienced this? How was it fixed/resolved? We tried the travel trailer on 2 other trucks without the issue, so we are confident the issue is with the truck and not the trailer. The trailer does not have LED lights as I've seen in a couple other posts that it can be the cause of the fault.

Thanks in advance!

 

Hi everyone,
We purchased a 2021 F-150 3.5L ecoboost and when we connected it to our travel trailer, everything seemed fine. 10 minutes down the road we got a message on the dash "Trailer Light Module Fault" - the brakes, left/right signal and 4 ways weren't working, but the night lights on the trailer were still on. Has anyone else experienced this? How was it fixed/resolved? We tried the travel trailer on 2 other trucks without the issue, so we are confident the issue is with the truck and not the trailer. The trailer does not have LED lights as I've seen in a couple other posts that it can be the cause of the fault.

Thanks in advance!

 

I had a bad ground on my boat trailer that caused similar issues on my 15.

 

We ask that you not post the same question in multiple forms. Thanks.

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Are u missing a you?

 

We bought our 21 F-150 in November 21 and drove it across Canada with a trailer. Everything was fine until we got into wet conditions. That’s when the Trailer Lighting Module Fault issue started. It got worse with worse conditions to the point no lights worked on the trailer except the market lights as described in the post. This occurred with 3 trailers as we rented a couple different uhaul trailers as well and had the exact same issue. The truck is in for service now, and we’ll see if Ford fixed the issue. There was recall work for the trailer brake module but I don’t know if that’s going to solve the light issue.

 

we did the recall on ours and it still isn’t working. They also replaced the junction box and fuses in the truck and it still persists. We are taking the trailer to the dealership once again but it’s now almost a year later and no known solution to the issue. We are at our wits end.

 

Did you do the big three?

1) Clean out and grease the 7-pin and four-pin, and the trailer plug.
2) Clean out and grease the two wiring connectors, first is the other side of the 7-pin (behind the bumper), second is a little way down the wiring harness.
3) Disconnect, clean, and grease the ground strap for the wiring harness back there.

If still no lights, having confirmed the trailer lights do in fact work, put a meter on the following to see if you're getting 12v there for the lights you are missing:

4-way: LH Stop/Turn, RH Stop/Turn and Park lamps all originate at the BJB (Battery Junction Box) and travel through either two (Park) or three (LH/RH) other connectors along the way.

7-way: Park originates at the BJB and travels through one connector along the way
LH Stop/Turn, RH Stop/Turn and vBatt all originate at the TRM (Trailer Module) above the brake pedal in the cab, and travel through one connector along the way.

 

I’m having an issue with just the right brake light, everything else works. Jumped the connectors on the trailer plug and the brake light works. I’ve seen elsewhere that there are a few people with the same problem. When I bought the trailer brake adjuster a new module came with it so I installed that as well. What doesn’t make sense to me is that the right turn signal works but the brake light doesn’t. Also, it was working when we used it previously. I guess it is possible the module went bad…thoughts??

 

My truck is having the same problem. in addition to that, it tells me reverse brake assist is unavailable. My dealer replaced the module and it still did not fix the problem. In fact a new error code is being shown on the dash " trailer brake module fault"