What will happen to the radio code when he disconnects the battery?

Take the OBD plug out of the beemer and look at the back side. There's only 3 or 4 wires connected. It is NOT a full OBD connection.

Round plug is the only way if in limp.

Wifey has same car and I have an E38. The E38 went into safe mode because the battery voltage was low. I bought a new battery and monitored voltage across the terminals when running. Should be 13.5V or thereabouts. Turned out to be the $500 water cooled alternator which I replaced.

Anyway it may never just reset because either your battery or alt is shot. Monitor voltage at the battery and confirm system is charging...
I googled my problem at the time..some shops replaced the tranny as they try and lock in 1st or 2nd in safe mode :lolhit:
and..have fun!

I was thinking again ;) about the E46..I had similar issues with that car but not sure it went fully into safe mode. First thing I did was replace the battery..about a year ago. Anyway a place to start if it has the original batt which is 10 yrs old. Testing it may be a pain since its buried in the trrunk..putting it on the charger may elevate its voltage and perhaps clear the safe mode..if it is the battery. Hopefully not a hard lock from something else as Bill suggested..
Lane

im a factory trained tech for bmw 8years at the dealer, with my own shop after hrs for everyone at a way way lower labor rate..pm me if you need a hand..im in Novi/walled lake area