GMC Troubleshooting Questions? Ask a Mechanic for Answers
Hello and welcome to just answer. You have an intermittent open circuit in the trailer's electric brake circuit somewhere between the trailer connector and the trailer brakes themselves. I doubt both trucks have an issue. It is the trailer wiring causing this. Have a RV shop or trailer repair shop check the connector and wiring for the brakes. I am 98% sure that is the problem.
You see the truck's Integrated Trailer Brake controller can sense when there is an open circuit or no load in the trailer's wiring harness. Something is wrong with the trailer brake circuit in the trailer. I hope that makes sense.
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