How to program a GM Keyless Entry Remote Key Fob (21997127)
You must have all remotes including working ones when performing this procedure. (This procedure essentially wipes all remotes from the vehicles memory so all must be reprogrammed
1. Close all doors on the vehicle.
2. Insert key into the ignition.
3. Press and hold the power UNLOCK button on driver's side door panel. Do not release until instructed to do so in step 5.
4. Quickly turn the ignition ON, OFF, ON, OFF. (ON is the position just before of starting your vehicle, OFF is the position where you can pull your key out of the ignition)
5. Release the power unlock button on the driver's side door panel. The vehicle should respond by locking and unlocking automatically. If locks cycle then continue to step 6.(if the door locks begin to lock and unlock BEFORE releasing the unlock button then the vehicle has not entered programming mode and you must start over. Remove key, open door and return to step 1. If the vehicle continues to lock and unlock before releasing the unlock button then there is a problem with the vehicles system and remotes must be programmed by a certified professional. If you are unable to get the door locks to cycle then you are turning the key too quick, too slow, there's a problem with the vehicles system, or the vehicle is not equipped with a factory keyless entry system.
6. Hold the LOCK and UNLOCK buttons on the remote at the same time until door locks cycle again. This could take up to 30 seconds.
7. NOW repeat step 6. for all additional remotes including working ones.
8. After step 6. has been performed for all remotes TURN ignition to ON to exit programming mode.
9. Turn ignition OFF, remove key and test all remotes to make sure that they are all properly programmed.