Bran new truck, have had it 2 1/2 months, but batteries have been completely drained 3 times already for no apparent reason. First time was after 1 month. Had to jump it to start, then again next morning before taking it to dealer. They had it 2 days and could not find cause and just checked and recharged batteries. Truck worked fine since until now. After taking it on an 1100 mile road trip, went to clean truck and found batteries completely dead when done. They were fine when I started as i was able to open truck, mirrors popped out, running boards came down and also opened the tailgate. Something happened over 30mins with multiple doors and tailgate open to take down 2 big batteries. Just realized the first time this happened was also immediately after cleaning truck. What could trigger a complete battery drain in little more that 30 minutes? Seems related to having doors and/or tailgate open. Have had issues with the tailgate since I picked it up, sometimes will just randomly open, other times will not close itself. Other crazy stuff happens like the welcome jingle when you first get in truck goes off with truck sitting empty and locked. Just happened to be close enough a few times to hear it. And after this latest incident after jumping it to start, headlights and driving lights randomly blink nonmatter what position light switch is in. Going to take it to a NJ dealer tomorrow, but am afraid they will not be able to duplicate issue and will just check and charge batteries and send her back. Any ideas?

Sounds like an electrical issue.

(Yes I know, we all already know that)

Hearing about the random stuff makes me think of bad grounds, but all of the random stuff tells me that something bigger is going on. I can't imagine what would discharge both batteries in 30 minutes without smoke coming out.

If it were me, I'd bring it back to the dealer over and over, make sure every visit is documented, and then either they fix it or you request a lemon buy back.

I'm not leading to a path of lemon-law action loosely. This is one of those weird ones that I have less confidence will be properly diagnosed and repaired by a dealership, unless you happen to run across a good diagnostician.

A few others also suggested potential grounding issue. And yeh you would think something has to melt/burn before discharging two big batteries in such a short time. Called GM directly yesterday and they promised to work directly with dealer to hopefully get this resolved. Was encouraged how willing they were to help right out the gate. Stay tuned.

Cool, looking forward to updates!