GMC 3500 Service Trailer Brake System Message

[2016frcard]

2017 TV having this message displayed. All was good until I borrowed a friends dump trailer (w/o electric brakes) Now I get this message displayed when hooking up 5'er. Have brake lights and turn signals when light switch is in auto position, no running lights at all. When switch is turned to headlights or parking lights, get nada on trailer. I don't see any brake "gain" level moving when applying brakes in transmission trailer mode when switch is in any position. YouTube has several similar but not exactly the same issue. Anybody experience this? Suggestions? Trying to avoid that dealer thing. Thanks in advance.

[Bama Rambler]

Have you checked all the "Tow" related fuses?
They're in the underhood fuse box.
Fuses;
#1 = Trailer Brake [Micro Fuse]
#2 = trailer Battery [Micro Fuse]
#14 = Trailer Stop/Turn Lamps, Left
#15 = Trailer Parking Lamps
#16 = Trailer Back-up Lamp
#17 = Trailer Stop/Turn Lamps, Right

[2016frcard]

Thanks for the quick reply. Yes, that was my first stop. Should have mentioned that in my post.

[Bama Rambler]

Then I would start at the 7-way plug on the truck checking for loose or bad/bent connectors. Take a goo hard look at the blades inside the plug as they can get sprung and/or bent back.

If it's not that, look at the connector above the rear differential for burnt connections.

[2016frcard]

Appreciate it, will check it out.

[Mr. Dan]

Do you have a plug outlet in the bed of your truck? If so, check where it ties in to the harness for the outlet in the bumper. My connection was bound up tightly with a cable tie but it was too tight and altered the shape of the connectors. So it lost contact now and then and triggered the warning message.

[cmysstailights]

Generally a ground issue. On the truck, spread the trailer prongs a little so they make better contact.

[2016frcard]

Will check thanks for the help.

[natedawg]

My fifth wheel started doing the same thing after sitting all winter.
Contact cleaner on both ends and plugging/unplugging a few times seem to have cleared it. I haven't seen the issue again. Once you get in the error state you have to turn the truck off to clear it, at least from what I have found. There may be a button combo to do it, but I never looked.

[gmjvlretiree]

Had that message come up half to my destination first time out this summer. Get a brass brush and clean you contacts on the trailer side. Worked for me.

[richp]

I had an occasional related problem because the receptacle on my '19 K2500 is a tiny bit large, and the plug intermittently works loose just enough to create the error message.

My solution was to wrap a small strip of Gorilla Tape around the plug to firm up the interface with the receptacle.

IIRC, other recent GM truck owners have reported similar mis-fit issues with the OEM female recepticle in the bumper.


FWIW.

Rich Phillips

[2016frcard]

Checked for wiring issues and found it at the adapter connection to the bumper
plug. (CURT part # 5600) Appreciate the help from all. Probably saved me $500 for that trip to the dealership.

[Mr. Dan]

Originally Posted by 2016frcard

Checked for wiring issues and found it at the adapter connection to the bumper
plug. (CURT part # 5600) Appreciate the help from all. Probably saved me $500 for that trip to the dealership.

Jolly good. Thanks for returning with that pic.

[cmysstailights]

That looks.nasty, glad u found the issue

[Bama Rambler]

Glad you found and all in all that's a pretty inexpensive cost for a fix.