ahh. OK. my yukon has all that stuff.

there was a small section for manual too but I was thinking you needed the complicated setup
​​​​​​I'll look

 

looked again.. there's basically nothing about the manual hatch but this blip and same wiring diagram above. just disregard stuff you don't have that's on it.

still need to test the relay is good. and if the body control module is sending signal to the relay and if not is the switch good. under common fixes it lists replacing switch.

 

Seems like a simple circuit, since you know the liftgate release motor works, I would next check the relay itself. If found to work, then check continuity of the green and yellow wires between relay and BCM. If you can, unplug the harness from the BCM and connect one wire to +12V and the other to ground. If that makes your liftgate open, then the BCM is not providing the signal. Either a bad BCM, or the BCM relies on the Liftgate Ajar Switch input to determine whether to open the liftgate or not. Does your Tahoe say the liftgate is open when it is not? Check continuity from Pin 12 of connector X6 on the BCM to ground. It should be open when the liftgate is closed.

 

it does not say its open when its not.... i have no idea what number or even where the relay is located.. I'm not too good with reading those charts