Only for BMW radio coded.
Security coding of the radio prevents unauthorized use of the radio after a power failure. The power is interrupted, for example, when the battery is disconnected, when the radio is removed, or when the radio's fuse blows.
If a security code has been entered into the radio, you must know the code before disconnecting the battery or before removing the radio. If the code is unknown, the radio can only be commissioned and operated by a BMW Dealership.
The individual code number is indicated in the radio passport. The passport should not be kept in the car.