If you are still within factory warranty, which I'm sure you are, you need to find a new dealer to service your vehicle. It's not GM that won't fix it it's your dealership.

This dealer is full of dung. A BCM replacement is the number one fix for this issue. The grinding brakes is also an easily fixed concern. Maybe when they say they called GM they mean GrandMother...

 

This happened to my '09 just yesterday and it was right after I had seen this from others. The morning temp was 59 and the guage stayed 59 all day. The next day it was back to normal.????