It is possible that it was completely dead for long enough, that key memory was lost. That is about the only thing that comes to mind. Try this procedure:
30-Minute Relearn Procedure
Use this procedure after replacing the following components:
" The passkey III (PK3) keys
" The theft deterrent control module
" The PCM, see important above
Important: This procedure is not available on vehicles equipped with option code (Z49 or BAE).
If replacing a theft deterrent control module with an GM SPO Replacement Part, perform the procedure to setup a new theft deterrent control module prior to the 30-minute relearn procedure.
With a master passkey III key (Black), turn ON the ignition, with the engine OFF.
Observe the Security telltale, after approximately 10 minutes the telltale will turn off.
Turn OFF the ignition, and wait 5 seconds.
Repeat steps 1-3 two more times for a total of 3 cycles or 30 minutes.
Important: The vehicle learns the key transponder information and/or passwords on the ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
With a master passkey III key, start the vehicle. The vehicle has now learned the key transponder information and the PCM has now learned the fuel continue password.
With a scan tool, clear any DTCs.
It might be advisable to look at your RPO sticker under your spare tire cover to see if it has options Z49, or BAE as mentioned above. You should probably have a charger hooked up to it so it don't go dead.
Monday, August 3rd, 2009 AT 9:06 PM