Hello everybody got a 2011 hhr with 52000 miles. Just started having problems this last weekend. While driving when cold bout 28 degrees outside the gauges will all start going up and down and the tranny will shift hard. sometimes theft light will come on but if you shut it off and restart it or let it warm up before driving its perfectly fine. Not really big on computers and electronics operating the whole damn car. thank you.

 

First thought is to check all of the fuses under the hood for proper seating. While you are in there push down on the top half of the box to make sure it is connecting properly with the bottom half.

Then pop the Darth Vader hood (just in front of the fuse box) off and inspect the connector to the ECM, and all of the wires coming from it for chafing or melting.

Could also be you need a new/correct T-stat. Your operating temp should be better than 180F, if it's lower the computer tries to do things.

Make sure you have enough coolant.

After that, I don't know until you get a CEL.