This isn't a malfunction—it’s a security feature. Blaupunkt radios are designed with an anti-theft system. If the power supply to the unit is cut, the radio assumes it has been stolen and locks itself. To prove you are the rightful owner (or that the radio hasn't been ripped out of a dashboard), you need to input a unique security code.
Sometimes the first attempt fails. Do not panic. Here is why: Blaupunkt Radio Code Calculator Online Free