Just some info on how the tailgate “lock” works so you can figure accordingly:
There is no actual lock solenoid, so there’s no lock and unlock driver circuits like there are for the door handles. It’s a switch on the tailgate handle, and two electronic latches. You press the switch on on the handle, and it sends a pulse to the BCM, who in turn, sends the release signal to the latches. If the BCM recognizes that the doors are locked, it ignores the signal from the switch. If the BCM recognizes that the doors are unlocked, then it will recognize the signal from the tailgate switch and allow the signal to the latches.