I am in the process of trying to install my navigation (15882766) in my 07 silverado ltz. Got it installed and theftlock popped up so brought it to the dealership and they tried programming it and it threw 2 codes for open circuits. I do not have a VSS harness and GM wont sell me one says the dealer ship. Is this why my navigation wont work or program? And where can I get one of these? How do I get ahold of JP Customs? I appreciate any replies.