Car radio codes deter theft. Removing a radio from a car disables the unit. Each unit is accompanied by a series of numbers called a "lock code." Entry of the code returns a disabled system to a normal operating state. The lock code is identified by the car's serial number. In addition, when a car's battery is disconnected, the car radio might lock.
Review your owner's manual. When you purchased your vehicle, you should have been provided a card with the stereo lock code. If your car is pre-owned, check the glove box or under the ashtray for the code. The previous owner might have placed the code in an easily accessible yet discreet location.
Obtain your car radio serial number. You might need to remove the faceplate that covers your stereo. Remove the screws that hold your console plate in place, then gently remove the plate that covers your stereo. Look underneath the stereo and on the sides. Copy the serial number. You might need to completely remove your stereo if the serial number is on the back.
Contact the car manufacturer. Search for the telephone number of a dealer near you. You can also find the manufacturer's customer-service number online. Tell the customer-service representative that you need your car's lock code. Provide your car's serial number. Copy the code in a safe location.
Turn your vehicle and car radio on. "Code" or "Locked" might appear. Enter your serial code using the numbered buttons. For example, if your code is 12345, enter the numbers "1-2-3-4-5" using the numbered buttons on your stereo. Your radio should begin working.