I have a 2022 GMC Sierra with the max trailering package. Yesterday, I hooked up the truck to my Boatmate trailer. Initially, it worked fine. The trailer display has worked fine on the other 3 to 4 times I've trailered this boat/trailer combo. Yesterday, I drove about 4 miles to the gas station. Topped off the boat's tank and began pulling away from the pump. While pulling away, the forward collision alert warning light came on and the display indicated the trailer was disconnected. I pulled over to see if the trailer lights were working and maybe a malfunction on the display. Nope. The lights and surge brakes did not work. I then tried turning the truck off and back on and disconnecting and reconnecting the 7 pin connection. Nothing worked. I have a Curt tester. It showed 12 volts but when I tried the brakes or other lights, the tester did not show any signals.
I checked the fuse for the FCA which was fine and put that back in. The FCA went off.
My wife brought her 4Runner up to the gas station and we hooked up the trailer to her truck. Lights and surge brakes worked fine.
I've searched through the internet and haven't found any fixes. There's a service bulletin that seems to blame a poor connection on the trailer. However, I think it's the truck. The trailer worked fine on my wife's Toyota. It's a brand new trailer. Prior to yesterday, the trailer was to the lake 2 times.
This is very frustrating.