2006 Pontiac Montana shuts off and says starting disabled.

You can try the theft deterrent relearn procedure listed below. If this does not work then you would have to take the van in for service. 1. Turn ON the ignition, with the engine OFF. 2. Observe the STARTING DISABLED DUE TO THEFT message on the driver information center (DIC), after approximately 10 minutes the STARTING DISABLED DUE TO THEFT message on the DIC will turn off. 3. Turn OFF the ignition, and wait 5 seconds. 4. Repeat steps 1-3 two more times for a total of 3 cycles or 30 minutes. 5. Start the vehicle. The vehicle has now learned the key transponder information and the PCM has now learned the fuel continue password. IMPORTANT: The vehicle learns the key transponder information and/or passwords on the ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle

The theft deterrent system is what disables starting. The relearn procedure works about 75% of the time. Typical charges for service are around $125 for a full diagnosis. If the body control module is bad and needs to be replaced, repairs can go up to around $500.

Your pk3 key is damaged. Pk3 stands for passkey gen 3 it uses a small resistor pressed into key under rubber head, use modus scanner or lap top w interface tool and program to change system perameters ie disable passkey 3 dealership can do this directly if certain peramaters are altered or deleted computer can have need to be re flashed