I can't help you diagnose or correct, but I can commiserate with you. We bought our '97 Bravada new in April '97, and the remote works only to lock the vehicle. The unlock and hatch do not work. I blame my wife - she uses her nails to push the buttons rather than her fingers.
Dealer wants way too much to replace the fobs and recalibrate. One thing you may or may not know - the keyhole in the rear activates ALL of the door locks - either lock or unlock. Faster than opening the driver door and hitting the unlock button.
Chris Beckwith