We just purchased a 2015 GMC Sierra DRW with the Duramax and integrated brake controller. I hooked up the trailer (a 2013 Lifestyle 36FW with the standard electric brakes) for the first time and I drove around my storage yard to set the gain on the brake controller. Then I went on the street for a longer test drive. During this test drive I started getting "check trailer wiring" popping up in the info centre followed a few seconds later by "trailer connected". I pulled into a parking lot thinking the trailer plug had popped loose but it wasn't loose. So I thought there was a loose wire from the installation of the in-bed plug that was installed using the factory 5th wheel wiring provision. I was using the in-bed plug that he installed. I did not try the factory plug at the bumper. I stopped in at the installers on my way home from work the next day and he checked the wiring he did and everything was fine. He also checked the factory plug and it was fine as well. Both had proper voltages.I don't believe there is anything wrong with my trailer plug as I never had issues like this with the old truck - a 2009 GMC Sierra DRW with the Duramax and integrated brake controller.Does anyone have any ideas on what else I can look for? Would putting di-electric grease on the in-bed plug and the trailer plug help?I plan to bring the truck and trailer to the installer when I have time so he can see both together.Thanks in advance for any help.

Check the trailers plug. Get a can of electrical contact cleaner and spray liberally both sides.

Sounds like you have a broken or loose connection in the factory harness. I would check at the back of the dash control and see how far I could trace the wiring.

I've noticed that sometimes the trailer plug doesn't stay seated very well in the TV. I have to push mine in extra hard to get it stay. Double check that you don't have any play in that connection.

The trailer plug worked without issue on my previous truck - a 2009 Sierra 3500 with the integrated controller so I thought it should be plug and play. All wires at both the factory bumper plug and the in-bed plug that the installer put in (using the factory wiring provision) had proper voltages when the were checked - I know - doesn't mean there can't be a loose connection somewhere. The message seems to appear when I take my foot off the brake pedal - not every time - but when it does appear it seems like I just took my foot off the brake.I will also get some electrical contact cleaner.Please provide suggestions if you have them for this problem.Thanks!

I had this happen a couple weeks ago and it ended being the main ground wire on the trailer frame. I was getting "trailer connected" "trailer disconnected". Should be a white wire coming out of the trailer side harness. I grabbed it to see if it was loose and it fell off in my hand. I've towed since then and all is good. Something to check. I looked it up before I checked it and it's pretty common.

2015 GMC Sierra 3500 - Check Trailer Wiring | Good Sam Community

CoMoCo
Explorer
Oct 07, 2015
blofgren wrote:
CoMoCo wrote:
Update - a lot of things have been looked at on the truck and the trailer. The hitch installer who also put the plug in the bed of my truck apparently spliced into a wire that should not have been spliced into. The GM dealer re-wired the truck's braking harness from the brake controller all the way to the plugs.

I was still having the "check trailer wiring" message after the re-wire. A trusted RV dealer found a wire at one of the trailer brake magnets was bad. The protective coatings were worn off and the wire was down to a few strands holding it together. The magnets were replaced (along with the wiring) and everything now appears fine. We just returned from a 450 mile round trip without any messages for the first time!

Just wanted to post a resolution to my problem - I was always thinking the truck was the problem. It was the trailer!
Yup; exact same problem that I posted about a few posts up.
CoMoCo
Explorer
Oct 07, 2015
rhagfo wrote:
CoMoCo wrote:
Update - a lot of things have been looked at on the truck and the trailer. The hitch installer who also put the plug in the bed of my truck apparently spliced into a wire that should not have been spliced into. The GM dealer re-wired the truck's braking harness from the brake controller all the way to the plugs.

I was still having the "check trailer wiring" message after the re-wire. A trusted RV dealer found a wire at one of the trailer brake magnets was bad. The protective coatings were worn off and the wire was down to a few strands holding it together. The magnets were replaced (along with the wiring) and everything now appears fine. We just returned from a 450 mile round trip without any messages for the first time!

Spliced????
New trucks and good adapters are plug and play should not require any splices!

Spliced - that's what I thought and the dealer thought that as well. They don't know what the installer was up to.
blofgren
Explorer
Oct 07, 2015
CoMoCo wrote:
Update - a lot of things have been looked at on the truck and the trailer. The hitch installer who also put the plug in the bed of my truck apparently spliced into a wire that should not have been spliced into. The GM dealer re-wired the truck's braking harness from the brake controller all the way to the plugs.

I was still having the "check trailer wiring" message after the re-wire. A trusted RV dealer found a wire at one of the trailer brake magnets was bad. The protective coatings were worn off and the wire was down to a few strands holding it together. The magnets were replaced (along with the wiring) and everything now appears fine. We just returned from a 450 mile round trip without any messages for the first time!

Yup; exact same problem that I posted about a few posts up.
rhagfo
Explorer III
Oct 07, 2015
CoMoCo wrote:
Update - a lot of things have been looked at on the truck and the trailer. The hitch installer who also put the plug in the bed of my truck apparently spliced into a wire that should not have been spliced into. The GM dealer re-wired the truck's braking harness from the brake controller all the way to the plugs.

I was still having the "check trailer wiring" message after the re-wire. A trusted RV dealer found a wire at one of the trailer brake magnets was bad. The protective coatings were worn off and the wire was down to a few strands holding it together. The magnets were replaced (along with the wiring) and everything now appears fine. We just returned from a 450 mile round trip without any messages for the first time!

Spliced????
New trucks and good adapters are plug and play should not require any splices!
Farmerjon
Explorer
Oct 07, 2015
glad you got it tracked down and repaired. that's frustrating and it turned out to be a dangerous fault as you wouln't have had much trailer braking power.
It's good that you had some good people to hunt that down.
Beaker
Explorer
Oct 07, 2015
My 2008 IBC was replaced under factory warranty. Don't remember what message but similar to what you quote; however I also had same messages when things were wrong such as loose connection.
CoMoCo
Explorer
Oct 06, 2015
Update - a lot of things have been looked at on the truck and the trailer. The hitch installer who also put the plug in the bed of my truck apparently spliced into a wire that should not have been spliced into. The GM dealer re-wired the truck's braking harness from the brake controller all the way to the plugs.

I was still having the "check trailer wiring" message after the re-wire. A trusted RV dealer found a wire at one of the trailer brake magnets was bad. The protective coatings were worn off and the wire was down to a few strands holding it together. The magnets were replaced (along with the wiring) and everything now appears fine. We just returned from a 450 mile round trip without any messages for the first time!
CoMoCo
Explorer
Aug 11, 2015
The installer looked at the truck and trailer and found a loose wire on the trailer plug (where the plug wires connect to the trailer wires). He also felt that there was a kink in the trailer plug so he replaced the trailer plug. I took it for a test drive and still had the Check Trailer Wiring message. Next step is to look at the trailer brakes and the wires going to the brakes. It may be a few days before this happens.
debraindi
Explorer
Aug 10, 2015
My LML flashes trailer connected and I'm aware of that also.
blofgren
Explorer
Aug 10, 2015
I had a similar issue with my previous truck/trailer combo with the aftermarket Prodigy brake controller. It drove me nuts until I pulled the trailer brake drums to check the linings and there was the problem on 2 wheels! There was too much slack in the wires going to the magnets and over time the insulation was rubbed off of the wires by the rotating brake drum causing a direct short. I rerouted and taped up the wires and the problem was solved.

This would only apply if you have drum brakes on your trailer, however. It would also explain the intermittent problem, which is exactly what I had. I have discs on our new to us trailer and no longer have to worry about that issue.

Hope this helps.

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