Around 2003 or so GM started linking the car radio Theftlock feature to the vehicles VIN. When you turn on the radio it checks the BCM for the VIN and if it is not correct- it won't work. For swapping into a similar car you need to get a stealership to program the new VIN into the radio. There are a limited number of attempts to get it right but If you mess around with it long enough it will permanently disable the radio. So if I wanted to install a 2005 Delco radio with this feature into an old car like ours, would it work? Does it need a VIN to operate or will it see no VIN and not activate the Theftlock? I have the '05 factory manual and one of the radio wires is labeled "Class 2 Serial data". I assume that is the link to the BCM. All the other wires are normal radio stuff like speakers, power, etc. If eliminating that wire disables the Theftlock it would seem too easy to believe, but if not, then it would indicate that this radio will only work with '03 and up cars.