I recently had a similar issues with 07' sierra with 97,000 miles. I would have intermittent power and would get all sorts of weird issues with the locks toggling on and off without hitting any switches. Also had codes for ABS, stabilitrack would go on and off, etc. I would recommend checking / changing the 175A mega fuse. A lot of the electrical systems on these trucks run on a very specific voltage and a small amount of additional resistance (corrosion on fuse) can give you all sorts of weird symptoms. My issues were resolved by changing the + battery cable ($50), replacing the mega fuse ($8), and cleaning all of the connections in the fuse block (free!). Hope this helps out and good luck.