I recently purchased a 1995 M3. I disconnected and removed the battery today and charged it for a few hours. After reinstalling it in the boot, I was unable to get the radio to accept the factory code. According to the instructions, if a beep sounds during entry, you must start the sequence again. The unit beeps always on the last numerical entry and does nothing. Does anyone have any ideas how to get beyond this road block and reactivate the radio?