How do disarm the anti theft system on a 99 Mercury Cougar?

To disarm the anti-theft system on a 1999 Mercury Cougar, 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, indicating the system is disarmed. You can then start the engine. If problems persist, consult your owner's manual or a professional for assistance.