the Passive Anti Theft System works using a transciever built into the security module of the vehicle. when the appropriate key is inserted into the ignition, a signal is sent from an antenna around the ignition tumbler to a computer chip built into the key. the key echos back an appropriate code that tells the computer its the right key for this vehicle. if the wrong key is inserted or someone attempts to bypass the ignition tumbler, the security module simply wont engage the starter or fire the injectors...making it extremely difficult to steal a PATS equipped vehicle.