Passive Anti Theft deterrent?

If you suspect that the anti-theft system is preventing your 2005 GMC Envoy from starting, you can try a few steps to reset it and get it out of fail-safe mode:

Check the Battery: Ensure that the battery is fully charged and properly connected. A weak or low battery can sometimes trigger the anti-theft system. If necessary, try jump-starting the vehicle or using a battery charger to restore sufficient power.

Turn the Key to the "On" Position: With the key in the ignition, turn it to the "On" position (do not start the engine). Leave it in this position for about 10-15 minutes. This can allow the anti-theft system to reset and reestablish communication with the key.

Disconnect and Reconnect the Battery: If the previous step does not work, try disconnecting the battery for about 15-20 minutes. Disconnect the negative (black) cable first, followed by the positive (red) cable. Reconnect the battery in reverse order, connecting the positive cable first, then the negative cable. This process can help reset the vehicle's systems, including the anti-theft system.

Try a Different Key: If you have a spare key, try using it to see if the issue persists. Sometimes, a problem with the key itself can trigger the anti-theft system.

If none of these steps resolve the issue, it's recommended to consult the vehicle's owner's manual or contact a GMC dealership or a qualified automotive locksmith for further assistance. They will have access to specific information about the anti-theft system in your Envoy and can provide guidance on how to resolve the issue.