Factory-issue car stereos sometimes come with an anti-theft device that renders the radio unusable unless you enter a code to unlock it. The code can be activated by disconnection of the car battery — for example, when the vehicle is being repaired — or if the stereo has been disconnected from the vehicle wiring. Reactivating the radio requires entering the unlock code, which you will have in the vehicle paperwork or will have to obtain from a dealer. Writer Bio
