How do you reset the anti theft on a 2000 Cadillac dts?

To reset the anti-theft system on a 2000 Cadillac DTS, insert the key into the ignition and turn it to the "On" position without starting the engine. Leave it in this position for about 10 minutes until the security light turns off. After that, turn the key to the "Off" position, wait a few seconds, and then try starting the engine. If the anti-theft system continues to activate, you may need to consult the owner's manual or a professional for further assistance.