To unlock a car radio that has been code locked you need to enter the code stored at the factory. In some cases you may need to go to the dealer to have the code entered if you do not have the original.
if by unlock you are talking about the theft protection feature on mercedes-benz another high end companies the answer is simple. You cannot unlock without calling the dealer with the serial number off the top of the radio head unit.
Well typically there is some security code that has to be entered by pushing button. Contact a dealer to find out what code you is. Some stereos though may have to be reset by a dealer.
