Car radios that are equipped with a theft-deterrent device will stop working whenever your car battery runs out of power or gets disconnected. The device's lockout feature, which is intended to prevent thieves from operating a stolen car radio, creates an inconvenience for the motorist who is locked out of his own audio system. Fixing the problem is easy if you know the numerical code that will unlock the theft-deterrent device and reset the radio. Otherwise, getting your radio to work again will take a bit of extra effort, and you might need outside help.
Check your operator's manual to verify that your car radio is equipped with a theft-deterrent system. Make sure the radio isn't working, and watch for a message that your radio might be displaying. The message could be "CODE," "INOP," "LOC" or something else. These messages indicate that you will need to enter a numerical code to unlock the radio.
Locate the document that lists the special numerical code to unlock your car radio. This document, often the size of a business card, should have been included in the paperwork you received when you bought the car. The code probably will consist of four or five digits.
Seek help from an outside source if you cannot locate the code for your car radio. Go online to see if your car's manufacturer has a website where you can get assistance, or make an in-person visit to an auto dealer affiliated with that manufacturer. In both cases, you should be able to obtain the code number, but you will need to provide detailed information that proves you own the car. Some websites that are not operated by auto manufacturers claim they can provide the correct codes to unlock car radios.
Punch in the appropriate digits to unlock the radio. Use the radio's preset buttons. This will enable the radio to resume normal operation, and you can listen to music while driving once again.
If you make a mistake when you enter the radio code, you probably will not be able to reverse the error. Instead, just finish punching in the appropriate number of digits. Then try again.
Do not try to guess the code that will unlock your car radio. Thousands of combinations are possible. If you enter the wrong code too many times, many car radios will prevent you from making another attempt until you leave the radio on and undisturbed for at least an hour.