How do you reset the radio Cadillac STS anti theft?

To reset the radio in a Cadillac STS after the anti-theft feature has been activated, first turn the ignition to the "On" position without starting the engine. Then, press and hold the radio power button for about 10 seconds until the display shows "SEC" or "LOCK." After that, enter the correct security code if prompted, which can typically be found in the owner's manual or obtained from a dealership. If the code is entered correctly, the radio should reset and become operational again.