[my99cavy]

Install a scan tool.
Turn ON the ignition with the engine OFF.
Select Body Control Module
Select Special Functions.
Select Program Key Fobs.
If you are adding a transmitter to the system, or are replacing a transmitter, choose the Add/Replace Key Fobs option. This allows new transmitters to be added without deleting those currently programmed to the module. If you are replacing all transmitters or none of the transmitters are working, choose the Clear memory and Program All Fobs option. This prevents lost or stolen transmitters from being used to access the vehicle.
Follow the scan tool on-screen directions.
After programming the last transmitter, remove the scan tool.
Exit the vehicle. Attempt to lock/unlock the doors to verify the programming.
Operate the transmitter functions in order to verify correct system operation.