here's what i found:
All transmitters which are to be recognized by the remote control door lock
receiver (RCDLR) must be programmed in a single programming sequence. If the
system is placed in program mode it will erase all previously programmed
transmitters upon the receipt of the programming signal from the first
transmitter. Up to four transmitters can be programmed. Do not operate or
program the transmitters in the vicinity of other vehicles that are in the
keyless entry program mode. This prevents the programming of the
transmitters to the incorrect vehicle.
Install a scan tool.
Turn ON the ignition, with the engine OFF.
Use the scan tool in order to access the Body Control Module (BCM) Special
Function: Program Key Fobs menu.
The scan tool must stay connected until all of the transmitters are
Press and hold the LOCK button and the UNLOCK button simultaneously on one
transmitter. After a delay of 15 seconds, the horn will chirp three times in
order to confirm the programming of that transmitter.
Remove the scan tool.
Operate the transmitter functions in order to verify correct system