Cate&Rob -- wasn't able to capture the video from the laptop (sorry). There are a few "As Built Codes" in the TRM module but it's hex gibberish. That module may be specific to my '17, as there is a lot of information (search engine results) stating the TRM is related to the trailer charging system.

After reading the (very long) thread at https://www.ford-trucks.com/forums/1...-messages.html one possibility is it's moisture in the connector that connects to the BACK of the 7-pin connector.

As summarized on other sites, Trailer Disconnect Warning Light Troubleshooting on a Ford Truck I checked on Ford truck message boards and the most common two reasons the Trailer Disconnect Warning comes on is either that there is corrosion or water in the trailer connector, there is a short on the wiring behind the trailer’s connector

What's maddening is the dates on these threads goes back YEARS. Surprised I haven't encountered it.

From a YouTube video: UPDATE: this turned out to be water making its way into the T adapter our upfitter installed along with the 5th wheel connection in the bed of the truck. Dealer and upfitter kept pointing fingers at each other. Dielectric grease the plugs myself, no help. Eventually I decided to crawl under the rear and trace the wiring from the bumper mounted connection and look for something loose. When I came to the T adapter running up to my outlet in the bed I disconnected it, about a half cup of water spilled out. Dried it out, applied dielectric grease then sealed around the openings with plumbers tape and electrical tape over the top. It’s been 6 months now, lots of heavy rain and no hint of the problem again. Hope this helps!

Yet another post said it's a ground issue between the EoH controller on the trailer and the truck. Is the EoH controller's ground wired directly to the 7-pin's ground wire? (Both to the frame doesn't count.)

One guy was convinced the issue was the grounding so...To test this theory, we used jumper cables to connect the bottom of the 5th wheel hitch (up above the king pin) to the hitch rails in the bed of the truck. The next 200 miles resulted in 2 "fault" alarms (instead of one every 10-30 seconds) and ZERO "disconnected" alarms.

Good luck finding this fault, Rob! If anyone can track it down it will be you.

howson
Hi Howard,

I really appreciate the research that you have put into this! I am travelling, but the limited reading that I have done is in the same vein as your findings. When I get home, I will be able to drop the spare tire (much of this wiring is in/under/around the spare) and open up every connector. I will document my findings, dry everything out and pack with dielectric grease. I hope this is a "physical" issue that I can remedy . . . rather than something buried in the diagnostic software. I can't imagine the dealer being much help on this (through no fault of their own). How do you bring in your truck for repair of an intermittent electrical problem that only happens when towing a 5th wheel trailer ???

Rob

Would one of those 7 pin trailer plug testers work to simulate whats happening?
https://www.amazon.com/CURT-58270-Ve.../dp/B001EOWQY4
https://www.amazon.com/7-pin-trailer...er+plug+tester
Just a thought
Keith

Unbelievable.

Cate&Rob Rob I once pulled a trailer that had a wiring fault in the brake magnet wire (wire was rubbing the inside the drum). My Tekonsha would detect the fault when driving (intermittently as your truck is showing) and when stopping, it would short out tripping the controller causing the brakes to stop working, then reset and restart working. Real pain, dad found it for me after yanking all 4 hubs.

Jlawles2
It is possible that the feedback from my EoH trailer brake actuator is not what the truck is expecting to see . . . but I am not sure how to go about resolving this.

​​​​​​​Rob

Rob, can you temporarily disconnect the system? The diagnostics in the truck will check for trailer lights every time, but lack of trailer brakes should not affect the system. Not seeing what it expects would trip the warning though. I would not plan on traveling a long distance without brakes nor would I plan on doing it in anything other than flat terrain. I knuckle busted pulling the hills of south west Arkansas for a few miles till I could pull over and plug in the trailer. Truck brakes did handle it well, but not something I would plan for every tow.

Cate&Rob howson I had this intermittently on my 2019, ironically what seems to have gotten rid of it permanently (knock on wood) was installing my EoH system (which I know you are already running). I replaced the plug on my umbilical and that resolved it but it came back. I pulled all the connectors under the bed and packed them all with dielectric grease, but no luck. I remember coming across the post Howard mentioned about the connector full of water but never found that smoking gun. I was going to run a new wire back to the brakes just to rule that out, but replaced them with hydraulic before I went that far. I know it started with the new truck, but I would be inclined to think its on the trailer end. Certainly check all the connectors under the bed, but maybe run a new set of wires temporarily to the brake actuator and bypass the umbilical, or also you could disconnect the actuator and tow a bit with no brakes to see if it trips the disconnect warning? If your umbilical will reach you could try the bumper connection instead just to rule that out? I bought an extension to try just that and had the same problem at both connections unfortunately.

Cate&Rob Don't know if it could be related but when we started towing with our then new 2020 F-150 with max tow we had a similar issue. Turned out that what I would call the master ground on the firewall was not cleaned, it had paint under it nor tightened properly and was providing an intermittent fault to random systems that was not traceable by the dealer. One day driving down the road the entire vehicle went off-line and we were left on the side of the road wondering what the heck. After 3 days and lots of "We don't know" from the dealer they brought in one of their retired techs and he found the issue right away. Since that time we have not had any fault notifications unless something was actually wrong. Was that ground issue the cause, who knows? Over the years I have found that grounding issues can be sneaky. We had gremlins with an avionics system in an aircraft that drove us nuts for several months. We finally reconstructed the installation from the bottom up (about 4 days) no more gremlins afterwords.



Dave

Rob
Have you tried deleting your trailer set up on the truck, then setting up a new trailer. There was a you-tube video on getting a trailer warning when Not connected. and the cure was to manually say the trailer was not connected (he scrolled through a lot of fittings), or just delete the trailer from the system, and set up a new one before the next trip. Seemed to work for folks.

I also found this - have no idea if it will help https://www.obdgenie.com/

Now what's strange in all the TBC Ford videos and others (including the Ford manual) no one covers selecting the brake type. I am assuming it is after you select the trailer type. I was wondering if you have tried a different configuration?

Just brainstorming

Keith

Rob Cate&Rob - sounds like time to get a new RV to match the new truck.......that'll fix it !

Dan

Canyonlight Dan, I think Rob would get rid of the truck before the trailer with all the stuff he has done to the trailer. He would hate to start over on all of the things he has changed or upgraded to a new camper (or at least I would).

flyfshrockies
Hi Dave,

I appreciate your advice (actually reminder) on the important a clean zero resistance ground path. I have been "bitten" by this before. When I get home, I will dissect this wiring and report back on what I find.

Rob

Canyonlight Jlawles2
Dan & Joseph . . . you are both right . . . LOL!

Part of the reason for getting a "much bigger" truck was to open up the possibility of a bigger trailer. But, when I think through all the things that I have added to this one, I don't really want to start over.

​​​​​​​Rob

ncitro howson
Hi Neil & Howard

I have narrowed the fault to happening after I release the brake pedal after an extended braking event (through which the trailer brakes are working correctly). So . . . what information is the truck looking for from the EoH actuator? I have a BrakeRite actuator. What brand do you guys have? (I know that Howard's is different than mine) The simplest solution to this might be a new EoH actuator . . .

Rob