Unplug all the wires from the remote start and see if the trouble clears. After all this time I doubt if the remote start was miswired but it might have failed internally. Unplugging it should clear the problem if it has.
I'm not saying they aren't right in this situation but most dealers will blame anything and everything on an aftermarket mod even though it may not actually be causing the problem. It's an easy out for them. If you can't get any help from the dealer, go back to the guy who installed it and tell him what the dealer said and maybe he can help rectify the problem.I have a 2006 CTS. I purchased a remote start for the car 16 months ago. Last week pulled up into the driveway and I couldn't get the key out of the ignition it wouldn't switch from accessory back towards me. Also I am able to move the shift lever from park into gear without putting my foot on the brake. Temp. and fuel guages are not working. All this at the same time. Dealer is telling me that the remote start is the cause of the problem and that the installer tied into the C2 harness which will void the warrenty. Any help?