actually try this it worked on my 03 gmc
1.Close all the vehicle doors.
2.Insert the ignition key into the ignition lock cylinder.
3.Press and hold the door unlock switch.
4.While holding the door lock switch in the unlock position, cycle the ignition ON, OFF, ON, OFF.
5.Release the door unlock switch. The doors will lock and unlock to confirm the program mode.
6.Press and hold the LOCK button and the UNLOCK button simultaneously on one transmitter. After a delay of approximately 15 seconds , the doors will lock and unlock to confirm the programming of that transmitter.
7.Repeat the previous step to program up to four transmitters.
8.Turn the ignition switch to the RUN position in order to exit the keyless entry transmitter mode.
9.Operate the transmitter functions in order to verify correct system operation.