Having the exact same issues in my truck, started about 6k miles ago around 34k miles on the truck. Service stabilitrack, radio, and HVAC all went bonkers while driving, my car briefly shut down on the expressway then started back up. Brought it into the dealership they said its probably the aftermarket remote start (on the truck when I bought it).
A few weeks ago the Service Theft Deterrent System started going crazy. I would try and start my car and nothing was on even the dome lights were off. Tried the back up key, no dice same issues,
I have LED license plate bulbs, HIDs from RFS, and a light bar tied to my brights via a relay (t tap that triggers the relay). I'm pretty sure none of these are causing my issue.
Has anyone found a resolution or any update from GM for this Theft Deterrent issue? I may replace my battery just to rule that out.
I'm at 40k so just out of warranty. Contacted my dealership this morning on this issue and sent them a bunch of other forum links to the same Theft Deterrent discussion. Waiting to hear back from them. I would hate to get stranded with my kids in the truck when the Sierra decides it was to not start...