Most car radios come with an anti-theft feature. It automatically locks your radio if it is removed from your car or the car's battery dies. When your radio has a lock on it, it is inoperable. You can unlock the radio with a numerical code. You could do this procedure yourself, or you can take it to your manufacturer.
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Locate the radio code in one of two ways. Look in your user manual for the anti-theft radio card. It will have your radio's serial number and unlock code. Second, call your manufacturer and ask for an unlock code. Provide your radio's serial number for proof of ownership.
Insert your key in the ignition and turn it to "On." This turns on your radio. Wait for the radio to turn on and say, "Locked" or "Code."
Press the "Tune" button. Look for the screen to go blank. Press "Tune" again to enter the first number.
Press and hold the button until you reached the right number. Repeat this step until you correctly entered all the right numbers of the unlock code. Your radio will automatically unlock once entered.