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Resetting GM Vehicle Theft Deterrent Systems

Ignition Cylinder diagram

If you replace the power control module (PCM, computer) or pull/replace fuses in the PCM in a General Motors vehicle, the vehicle theft deterrent (VTD) system will require a reset. There are three systems in use by various General Motors makes and models in this regard. They are the VATS, Passlock, and Passkey III systems. Each works slightly differently has its own VTD reset procedure.

The VATS and Passkey I & II systems use a resistive chip ignition key, which is a chip inside the key itself that communicates with the vehicle’s theft system to validate the key so the ignition will turn. The Passlock system uses a coded lock cylinder for validation. Passkey III uses a transponder in the ignition key or keyfob to exchange passcodes to validate the key.

In the VATS and Passkey I systems, a separate Theft Deterrent Module (TDM) validates the key. This system uses a simple resistance chip to determine whether the key is genuine. Each key is coded with a specific amount of resistance to a given amount of power. On these systems, replacement or repair to the PCM or its fuses should not require reprogramming of the TDM if the key hasn’t changed.

On a vehicle equipped with Passkey II, the TDM is located in the Body Control Module (BCM), but otherwise works the same way that the VATS and Passkey I systems do. This system will require a reset of the VTD, however, when the PCM has been worked on. Start with a fully charged battery in the vehicle because the process can take as long as 30 minutes without the vehicle being capable of running to recharge. If everything is working correctly, the following procedure will reset the VTD.

Insert the key into the ignition and turn to the “On” position, but do not turn to “Start.” After leaving the key in this position for 11 minutes, the security light should shut off (it will be flashing or steadily on otherwise). Turn off the ignition for 30 seconds, but do not remove the key. Turn it back on (no start) for 11 more minutes. Then off for another 30 seconds, and back on for another 11 minutes. Turn off for 30 seconds, then on for another 30 seconds, then off. Wait a few seconds and then attempt to start the engine. It should be allowed a start.

With the newer Passlock system, a coded lock cylinder does the same work. The reset procedure is similar to the above, but with key differences. In a car, only one cycle will be required, but in trucks and SUVs, it may require all three to reset it. Turn the ignition to the “On” and then the “Start” position and back to the “On” position. If the security light is on, leave the key in the “On” position and wait for ten minutes. The light should turn off. Then turn the key to off, wait 10 seconds, and attempt to start again (briefly) and release the key to the “On” position. The security light will come back on. Wait ten minutes until it shuts off. Turn the ignition off, wait ten seconds, then repeat the start-to-on and 10 minute wait. Turn the ignition off, wait 10 seconds, then start the engine. It should fire up, but will likely leave trouble codes for the attempted starts. You can safely clear those with a scan tool.

Finally, the new Passkey III system is the latest and easiest to reset. It is similar to the other resets. Turn the key to “On” without going to “Start.” When the security light comes on, wait for ten minutes until it turns back off. Turn the key off for five seconds and then back to the “On” position. The security light should come back on. Wait for ten minutes until it turns off, then repeat the off for five seconds and back to on. In some vehicles, the security light will flash and then stay off. You’re now reset. If not, go through one more cycle of 10 minutes with the light on, then turning the key to off when the security light turns off. The vehicle should now start. You can reset additional keys at this point if you put them in within 10 seconds after removal of the previous key. Put in the new key and turn it to “On” without starting. When the security light shuts off, the new key is programmed - usually less than two seconds. You can program as many new keys this way as you need.

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