2015 GMC Sierra 3500 - Check Trailer Wiring
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 dro...
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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.
