Many car stereo manufacturers produce car stereos that prevent theft by requiring a unique code. Removing the stereo from the vehicle disables the unit by requiring the entry of a specific code. The codes are attached to the unit by serial number. In addition, when a car's battery is disconnected, it may cause your stereo to "lock," requiring the entry of the code to enable usage.
Retrieve your car radio code. You should have received your code when you purchased your vehicle. Check your car's owners manual. If you have lost your code, contact your car's manufacturer and provide them with the serial number to your car stereo. They should be able to provide the code.
Turn your vehicle and car radio on. The word "Code" or "Locked" may appear. Enter your serial code using the numbered stereo buttons. For example, if your code is 24367, enter the numbers "2-4-3-6-7" using the numbered buttons on your stereo system or touch screen. Some radios require you to repeatedly push the number "1" until you reach the correct number. If you have entered the correct code, your stereo should unlock automatically.
Turn your car off and wait fifteen minutes, if your stereo will no longer accept your input. Sometimes, if the number is entered incorrectly, you will have to start over again. Repeat the above steps. Contact your car manufacturer if you are unsuccessful in unlocking your stereo.