A method of preventing unauthorized movement of a transmission shift mechanism comprises the steps of: detecting a predefined event; moving a locking device into an engaged position with a shift mechanism upon the occurrence of the predefined event to retain the shift mechanism in at least one of a park, reverse, neutral, and drive position; and maintaining an ignition system in a substantially off position during the detecting of the event and the moving of the locking device into the engaged position. A vehicle assembly is also provided comprising the transmission shift mechanism and the locking device coupled to the shift mechanism. The vehicle assembly also includes the ignition system, which is movable between off, accessory, run, and start positions, and a controller with the controller energizing the locking device in response to the predefined event to move the locking device into the locked position while the ignition system remains substantially in the off position.