Can anyone help me unlock a GM 030078987746 Blaupunkt car 300f number 90 533 422 radio cassette player that came with the car but no manual or code. When the battery went flat the radio went dead.

You will need to contact a GM Dealer. Unfortunately, in my experiences, you can not get GM radio codes for free. Last one I got cost me $30 from the dealer after they unhooked the battery to perform a recall item repair. The reason they are not free is that the standard GM radios have the ability to hold a code but it must be one that is inserted by the owner. This being the case, there is no way that the dealer can know what the owner used as a code. The only thing that can be done with late model GM radios is the dealer has to reset it to remove the code and I believe that they have to remove the radio to reset it.

Once it is reset, you can leave it so that you don't have a code but it will also work for a thief if it is stolen or you can change it to a code of your choosing.

That was with a Bose premium sound system. Blapunkt may be different but I believe that all radios that go into GM vehicles use the same system.

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