2005 Hummer H2 DOOR LOCKS

It would at least require removing the liftgate trim panel, and checking that the linkage is connected. First, if you listen at the door, either internally or externally, do you hear any thumping when activated. This would at least indicate that a signal is getting to the lock actuator. If after determining there is no noise, and the linkage is connected, you would need to check if a signal is getting to the lock actuator. You can do this with a test light across the two terminals. It should light with either command, the circuit just reverses polarity. See if that gets you anywhere.