Wiring question /wiring diagram for tailgate
 

Trying to fix wiring issues.
When I press the hatch button on the key or on the center console, only lower tailgate opens, not the upper.
So basically it's blocked and I can't open the upper tailgate. Because if the bottom unlocks but not the top, I can't open it.
I think it's working in reverse lol. These buttons should be opening the upper tailgate, not the lower one.

My wiring might be messed up, long story.
I'm missing a relay for the upper tailgate, and I can't for the life of me remember if I accidentally removed it, thinking it was another relay that I didn't need, or if u never had it.

With wiring as it is right now, if I ground Pin 2 on connector X1739, it unlocks the lower tailgate.
https://i.ibb.co/cyHMSfT/Screenshot-...946-Chrome.jpg

At this point I'm not sure I can untangle what's wrong with the wiring, but maybe if both upper and lower tailgates open at the same time, it'd be good enough.

So my question is simple.

What has to happen on this diagram for the latch to open? Measured voltage on all 4 pins, pin #4 has 13 volts all the time.
https://i.ibb.co/F5jdWJZ/Screenshot-...518-Chrome.jpg
https://i.ibb.co/TqZTw8m/Screenshot-...523-Chrome.jpg

On pre-facelift that top tailgate lock motor actuation voltage (MERHK) comes directly from GM. On facelift models that voltage activates a relay for the actual supply voltage. There should be voltage only briefly when GM activates opening of the lock.

When the lock is open that flip switch in the diagram changes position. The grounding line to GM (HK) is opened so GM knows the hatch is open. And the same switch connects ground to trunk lighting (HECKKL.).

The opening buttons or remote should only open the top tailgate. The lower tailgate is only opened with the switch button on the lower tailgate.

Wow impressive, thanks so much for your help!
It clarified a lot of things for me.
That's really great to know that pre-facelift model doesn't have a separate relay for the top tailgate.
I don't know how you know this stuff, but it's great knowledge:)

Now I know I had no relay for the top tailgate, as my X5 is pre facelift.
So I know I'm not crazy, I didn't delete it and I remember the top tailgate working before.

It sounds like the GM is the problem in my case.
Because you're saying that pin 4 should only have voltage momentarily, while mine has it all the time.
So then maybe a bad GM module which burned the motor (M120) for the switch?

That info relies on WDS diagrams.

It sure sounds like failed GM if there really is permanent voltage on lock actuation line yellow/brown wire (if it's wired correctly). You can measure the actuator resistance if the coil is burned or not.

I'm my own worst enemy lol.
I thought I'd install the latest GM module, and I guess the module I installed was for later E53 model. And this module is probably programmed differently. Like you said, for two relays for each top and bottom tailgate.

https://i.ibb.co/Wvj5txx/20220824-201534.jpg

So no surprise that the button on the lower tailgate wasn't working at all. And the button on remote starter and dasboard for rear tailgate was opening lower tailgate, not upper.

Well I placed an old GM module back, and the button for the bottom tailgate now works and opens the lower tailgate.

And when I click on the button for the upper tailgate, or use the remote or push the button on the dashboard, I can hear the clicking of relays, but upper tailgate doesn't unlock.
I figure the motor is dead from putting the wrong GM?

The upper tailgate motor is tricky to remove, it looks like I need to remove the motor for rear window wiper to get it out.

I'll try to get it out, if resistance is low or 0, I figure it must be out of commission?

Got a new actuator from junk yard, now everything works again.
Measured resistance on both working and non working actuator between pins 1 and 3, both show 0.
Forgot the diagram, gotta measure pin 3 and 4.

Resistance between pin 3 and 4 on working actuator I'd 35 ohms. Resistance on non working actuator is infinite...

Also just wanted to share that the wiring on pre facelift and post facelift x5 is different for upper tailgate lunch actuators.