If you replace a key, theft deterrent control module or the powertrain control module you will have to perform a relearn for the car to start. Most of the Grand Prix of this generation will use Passkey 3 systems. PK3 will be stamped on the metal part of the key near the plastic head. Passkey 3 systems use a transponder in the key that uses radio frequency communication with a theft deterrent module (I suspect this is same as body control module) and the PCM to enable the fuel injectors and allow the car to start and run. If the communication is disrupted between any 1 of the 3 components your car will start and run for about 5 seconds before shutting down. I found a pdf formatted Tech Tips at this link
. I’ll reprint the instructions for Passkey 3 below. If you care to know why I had to learn this you can read my tale of woe at the end of this post.
In order to initiate the relearn
1. Insert a master key (black head) into the ignition switch.
2. Turn to the “On” position without starting the engine. The security light should illuminate and stay on.
3. Wait approximately 10 minutes or until the security light turns off.
4. Turn off the ignition switch and wait 5 seconds.
5. Repeat steps 2 through 4 two more times with the same key.
6. Turn the ignition off. The vehicle will now learn the key transponder information on the next start cycle.
7. Start the vehicle. If vehicle starts and runs normally, and security light is off, the relearn is complete.
If additional keys are to be relearned:
8. Turn the vehicle off.
9. Insert the next key to be learned and turn the ignition switch to the “On” position within 10 seconds of removing the previously used key.
10. Wait for the security light to turn off. It should happen quickly.
You may not even notice the light come on, because it will learn the key transponder immediately.
11. Repeat steps 8 through 10 for any additional keys.
Occasionally the theft deterrent features of your Grand Prix will do something unexpected. Recently when the temps were -25*F my Grand Prix left me stranded. After starting and running in the brutal cold and being shut down just 15 minutes earlier I found myself unable to restart the car with the only clue being a flashing security light on the dash. I had the car towed to a trusted shop where magically the car started and ran, but the security light would continue to flash for around 10 minutes. It cost me a tow and an hour of diagnostics time, but the shop tech didn’t have the software to reset the theft module and advised I take the car to a Pontiac dealer for repair – hopefully before it left me stranded again. Luckily I found the procedure to put the Passkey 3 system into a relearn mode. I’m happy that my car is back to being a reliable daily driver.