My keyless entry remote has always worked, and all of the sudden it just quit. Battery checked in remote as being like a new battery. I did the hold unlock and lock at the same time for 8 seconds and nothing happened. Anyone have any clue what to do?

If you search keyless entry programming there should be the GM instructions on how to program the transmitter correctly.

However, I have no idea if they changed the procedure for 04' and up. Sorry, most of us have the 97-03' models.

Have you tried Club GP?

http://www.automotiveforums.com/vbulletin/showthread.php?t=401909