How do you disarm anti-theft system on a f-150 2001?

To disarm the anti-theft system on a 2001 Ford F-150, insert the key into the ignition and turn it to the "On" position without starting the engine. Leave it in the "On" position for about 10 minutes until the security light turns off. After that, turn the key to "Off" and then attempt to start the vehicle. If issues persist, consult the owner's manual or a professional for assistance.