A: Interrupting the voltage to the battery has activated the radio’s anti-theft code. That way, if someone steals a radio, it’s useless.
Somewhere in the paperwork in the glovebox that the car came with should be a sheet of cardboard with the radio’s security code. If you can’t find it, you’ll have to go to the dealer and pay to have them reset it. If it gets to that, be sure they give you the code for next time.
