How do you reset a anti-theift system on a mercury mountaineer?

To reset the anti-theft system on a Mercury Mountaineer, first, unlock the vehicle using the key or remote. Next, 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, then turn the key back to the "Off" position and try starting the vehicle. If the problem persists, consulting the owner's manual or a professional mechanic may be necessary.