This unit does not actually require a code. If you own a late model Vauxhall or Opel, then you may be familiar with the CARPASS that shows the "Unlock" or "PUK" code used for vehicle diagnostics and programming, and it is often this vehicle specific code number that is described when people are advertising their radio for sale. This 4 digit number is unique to the vehicle, and will not allow the radio to be used in anything other than the original car.
You will often hear the term "Married" radio, and this is because the stereo is programmed with encrypted data that will only allow it to communicate with the original vehicle and no other, and the equipment used to program the stereo and the car together is called a Tech2 programmer. The Tech2 plugs into the diagnostic socket of the car and can then be used to perform various programming routines, one of which is to allow the radio and car to communicate with each other.
P.S. Really, AFAIK, it communicates not with the vehicle but with the display. So drive to your dealer to have it reprogrammed properly.
A.R.S., November 2012
