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GM Theft Deterrent Systems: VATS, Passlock, Passkey, Passkey II, and Passkey III

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Read more for an overview of GM theft deterrent systems and the importance of a relearn procedure.

Theft Deterrent System Functionality and Purpose

The theft deterrent system is designed to prevent vehicle theft by locking down the vehicle when the ignition or starting system is being tampered with.

  • Under normal operation, when the key is inserted into the ignition, the ignition lock cylinder sends a signal to the theft deterrent module, or body control module, allowing the vehicle to start.
  • If the ignition lock cylinder does not detect the correct resistor, magnet, or transponder chip in the key, the vehicle will not start, and the antitheft indicator light will illuminate on the instrument cluster.

    • After Replacing a Control Module, What is Required to “Relearn” the Key?

    The theft deterrent system is a common cause of a no-start condition after replacing an engine control module (PCM/ECM), body control module (BCM), lock cylinder, or theft deterrent module.

  • When replacing any module, on a vehicle, the key codes must be relearned to allow the vehicle to start.
  • The relearn can be performed by a factory scan tool, an aftermarket scan tool, or a simple manual key cycle procedure.
  • It is important to determine which generation of passive anti-theft system is installed on the vehicle.
  • Before starting the relearn, control modules must be clear of all diagnostic trouble codes (DTCs).
  • The battery must remain above 12 volts throughout the relearning process. Use of a backup battery or booster is recommended.

    • Watch & Learn More

    In this CARDONE Video , we will walk you through the different types of GM theft deterrent systems and their relearning procedures.