This past Monday, had this error come up. Since I don't have a trailer, I dismissed it. After running my errand, jumped in the truck, and when starting, the starter just clicked. I pulled the negative cable and reconnected. Started up, but didn't seem to crank as fast as it normally does. Next day, was going to do something, and truck is completely dead. Put my charger on it at 20 amps for several hours, and truck started fine. Saturday, I made a Home Depot run, and the error message popped up again, and went away on it's own. Get done in Home Depot and it acted like the battery was completely dead. No spark when I disconnected the negative battery cable. I left it disconnected for about 10 minutes and this time when connecting the cable back up, it sparked a little. Truck started with plenty of cranking power. Seems to be related to the trailer breaking system.
Any thoughts for a fix? This truck is the biggest piece of junk I've ever owned, should have waited until I could find a Tundra or F150. I'll never buy another GM product again.