I have a 2007 Silverado Classic. I had the 6 cd changer radio. I have no Y91 or Y92 options. I bought on ebay a non-lux navigation unit that was taken out of a 2006 Trailblazer. I put it in, all plugs matched, etc. Turned it on the the THEFTLOCK ACTIVATED was on the screen. No problem. Took it to the dealer, and they say they cannot get to the nav unit, they cannot unlock it. Some points: the unt's GM P/N is 15800000 My truck is a 2007 Silverado Classic, Extended Cab Has Bose but not the lux package (Y91,Y92) I gave the dealer these instructions I found, but they said it didn't work: Radio Setup With RPO UM8 Radio Theft Procedure Complete the following procedure, using a scan tool, in order to properly set up communication: At the Main Menu screen, select: Diagnostics. At the Vehicle Identification screen, select the following options: Model Year LD Trk, MPV, Incomplete At the System Selection Menu screen, select: Body At the Vehicle Identification screen, select the following: Appropriate model Appropriate Air Conditioning Navigation Radio At the Body Screen, select: Navigation Radio. At the Radio screen, select: Special Functions. At the Special Functions screen, select: VIN Relearn. At the VIN Relearn screen, the scan tool will display "Do you want to clear radio theft information?" To begin clearing, press the soft touch key on the top right of the scan tool. The scan tool will display "Clearing Radio Theft in Progress." Press EXIT on the scan tool and cycle the ignition. I tried called GM, no help. I tried calling Delphi, no help. Can anyone on this forum help me? Give me instructions to give to the dealer to get the theftlock off? I appreciate it in advance.