GM Radio won't unlock

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  • greasybob
    Senior Member
    • May 2008
    • 1590

    GM Radio won't unlock

    Have a 2012 Tahoe here with a navigation radio that needs replacing. I obtained a used radio with matching part numbers and RPO code. I programmed the radio with GM AC delco TDS to get the proper setup. All the calibration numbers changed to match the vehicle but when programming was complete the radio remained locked. I'm not new at this and have done many dozens of GM radio replacements in the past. This the first one that would not unlock. I have no other codes in the vehicle and all communication systems seem to be working. I even tried a couple of internet solutions including open the door after programming and using Tech 2 enter the vehicle as an 06 Monte Carlo and try VIN erase ( B.S. That function is not available for that vehicle in tech 2). Any Ideas ? The programming process runs as it should, no warnings or other messages.
  • greasybob
    Senior Member
    • May 2008
    • 1590

    #2
    I just checked the VIN that is stored in the radio with the tech 2 (SnapOn software does not list VIN data for this module in this vehicle) and it does not match the VIN for the vehicle. The VIN stored in the BCM is correct for the vehicle. So the reprogramming is not rewriting the VIN into the radio, first time that I can recall running into this problem .

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    • Glide
      Senior Member
      • Jan 2015
      • 303

      #3
      You'll have to flash it with SPS.Any GM truck radio has been that way since 99 new style.
      Last edited by Glide; 03-25-2021, 04:11 AM. Reason: didn't read first post correctly

      Comment

      • greasybob
        Senior Member
        • May 2008
        • 1590

        #4
        That is what I have been doing. The calibration numbers change but the VIN is not re-writing during the flash for some reason. I noticed some substitution errors in the Theft Deterrent Module when checking last night, so I will try to correct those first. Did you know that Tech 2 Win will give you 30 instead of 3 just like GDS ?

        Comment

        • Glide
          Senior Member
          • Jan 2015
          • 303

          #5
          Originally posted by greasybob
          Did you know that Tech 2 Win will give you 30 instead of 3 just like GDS ?
          No I didn't.I have only used Tech2Win a couple of times as I have a Tech2.What interface are you using to flash? Do you have access to a MDI?

          Comment

          • greasybob
            Senior Member
            • May 2008
            • 1590

            #6
            I'm Using Pass Thru Pro 3. This is the 2nd radio that I've tried with this vehicle with the same result, so probably not the radio. No MDI available. I"ve done this many times in the past without problems maybe GM changes something recently, they're not to big on supporting used modules.

            Comment

            • Glide
              Senior Member
              • Jan 2015
              • 303

              #7
              Originally posted by greasybob
              GM changes something recently, they're not to big on supporting used modules.
              That is always possible.I've replaced newer radios with used,but not Nav.What was the issue with the original radio?

              Comment

              • greasybob
                Senior Member
                • May 2008
                • 1590

                #8
                It would light up but no functions, blank screen, no sound, no communication.

                Comment

                • Glide
                  Senior Member
                  • Jan 2015
                  • 303

                  #9
                  Did you check as per PIT4474E ?

                  Comment

                  • Speedybon
                    Junior Member
                    • Jan 2012
                    • 22

                    #10
                    It needs to go to the dealer. Programing Radios are very tricky. Programming any late Gm product is hard. And time consuming.

                    Comment

                    • greasybob
                      Senior Member
                      • May 2008
                      • 1590

                      #11
                      I'm kind of a sucker for the hard jobs. Should be able to do anything a dealer can do with the right tools. Most flashes go with out issues, used stuff is always a gamble. I just want to know if GM changed anything that would not allow the VIN to be re written or if any one else has seen this happen.

                      Comment

                      • Speedybon
                        Junior Member
                        • Jan 2012
                        • 22

                        #12
                        You will probably lose money on programming. We would build the car to show all options and download it with too an SD card. Some would take hours. Not a money maker. I would stay away from Radio programming.

                        Comment

                        • Glide
                          Senior Member
                          • Jan 2015
                          • 303

                          #13
                          As I said,I haven't tried a used Nav radio in a GM,but I found this info in service information "
                          It is critical to use the service replacement Communication Interface Module only in the vehicle for which it was ordered "
                          Another part of SI refers to the Nav radio as the communication interface.So maybe a new Nav radio has the VIN written to it before it is shipped to the dealer.

                          Comment

                          • SnapOnKid
                            Senior Member
                            • Jan 2011
                            • 870

                            #14
                            I have not done a used Nav that new. The one I did do,

                            I Tried reprogramming the software and It went through the entire process and said it failed near the end. I was thinking either the radio was messed up or maybe there was something else that needed to be done and there was a super secret trick that was not being esplained...

                            On the normal radios, I have to reprogram the software in order for the new vin to be learned and for it to unlock. Sometimes a standard vin reprogram will take and sometimes it will not but even when it does take usually the Radio remains locked. When I reprogram the software it seems to overwrite the vin and unlock it every time.

                            The 2nd time I tried to just re-write the vin. I verified by scanning the radio again and looking for the vin. When I cycled the Key, the nav unit came to life and was fully functional. I was in disbelieve... When I scanned the car again it had the correct matching vin.

                            I used a Genuine Tech 2 and used it as a passthrough when attempting to program.
                            But The Vin Unlock portion for the nav radio was in the scan tool and not the SPS subscription.

                            Comment

                            • Nate75
                              Junior Member
                              • Jan 2019
                              • 11

                              #15
                              after 2010 almost all GM vehicles wil not allow the vin to be changed in any module. I have tried several and ended up opening the radio up and swapping the smaller board that doesn't have the vin in it and it resolved the issues. there are systems out there to connect directly to the PROM chip and reprogram the vin, but I have not tried them.

                              Nathaniel

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