My truck dash shows “Check trailer wiring”,

[FredLueck]

Intermittent loss of trailer brakes, loss of side mirrors rear view cameras as well. Anyone have any ideas on why this is happening? RV is new 2023 Montana 5th wheel hooked to a 2024 Chevy 2500HD. Pin connector from 5th wheel to truck could be the problem I guess.
Any suggestions while I wait to bring it in to dealer? We have used the RV twice on short trips total of 25 miles, and 4 day total usage.

[Daryles]

Start with cleaning the contacts in the 7 way cable and the truck bed receptacle. I used #200 sand paper and "Deoxit". Roll up the sand paper to get into the female contacts.
Then a little dielectric grease on the contacts.
Open the pin box junction box and squeeze down on all the wire nuts.
Some people have found the wire going through the axle tube has Chaffed. They cut it off and spliced on wires on the outside of the tube and zip tied them on.

[ChuckS]

Newer GMC trucks have often had issues when connected to an RV.. There are many post out there regarding the issue... Usually truck problem.

Your truck is brand new so the 7 way connector should not be that corroded.
Truck Side Checks:
.. as stated visually check all 7 pins on truck side for any issue
.. use multimeter and measure the DC voltage out of the 7 way receptacle on the truck with a helper pressing the brake pedal

RV SIde :
YOUR YEAR Montana uses a GIGGY BOX and this is where the 7 way RV wires are connected ( each to a threaded terminal with nut ) .. check for any loose connections in the giggy box

Keystone video on Giggy box and inside the box on the lid is a schematic with wire code for the RV to truck 7 way cable
https://www.keystonerv.com/innovations/giggy-box

[ChuckS]

This link may also gives you more insight to your issue with your 2024 GMC

https://www.gm-trucks.com/forums/top...g-dic-message/

[Ahdmeyer]

this tool comes in handy to check the truck end

https://www.amazon.com/Oyviny-Traile...555826063&th=1

[jsb5717]

As stated, start with the truck and check the easiest things first. Your trailer is newer so I wouldn’t suspect brake wiring issues…especially if everything worked originally.

However, if you don’t find issues on the truck side then you’ll need to dig into the trailer side. When we got that “intermittent” message I eventually found 2 issues on our trailer.

1. A broken brake wire inside one of the wheel hubs
2. Worn wire insulation in the wires that ride loosely inside the axles. The only way to find this one is to cut one end of the wires and pull them out. So you’re forced to “fix” it before really knowing if it’s “broken”. But it’s a relatively easy operation and either solves the current issue or prevents a future one. Once the wires are pulled from the axle then rewire the ends and zip-tie them tightly on top of the axle. Our brakes have worked great since.

[Foldbak]

Typical issue with the GMC Infotainment system. Turn off truck, disconnect the 7way, start truck, connect 7-way. Has worked for me.

[High5er]

Had the same issue with a 2020 Chevy HD. I was never able to figure out what the issue was, but could confirm brakes and lights were working. The issue seemed to stop after an updates, so my issue seemed to be with the Infotainment system.