Re: Remote start not working
It may be an intermittent short in one of the door ajar sense circuits. Moisture (about that time of the year)? In order to test that theory, try unlocking all the doors and then relock them (with the key fob, of course). If it senses an open door, it'll pause a few second before locking (read the owner's manual on delayed locking). Or, it may shake it loose so the remote start will then work.
Also, if the warranty just ran out, you may want to call the GM customer service and ask if they could do anything for you.