When I use my remote starter & door lock/unlock and the lock/unlock button in the car, it does not lock or unlock both back doors. It does start the car, opens the trunk, and lock & unlock both front doors. In addition, the rear window defogger on my 2009 Chevy Impala is not working. I have heard that it could be the ground in the trunk is not tight, relay, fuse, or all of them. Any Ideas?