2016 Yukon Denali liftgate not working

[sbrekus]

Our liftgate has stopped working completely. When you press the rear button manually, the back lights flash but nothing happens. The front ceiling switch is on but does nothing, nor does the remote. I started basic troubleshooting by checking fuses and relay. Here is a photo of the rear compartment fuse box.

I consulted the owner manual and online diagrams. They all show a fuse in the 5 position and a relay in the 16 position both labelled “liftgate.” Both these are empty/missing on mine. So my first thought was that I found the problem, and need to replace them. Then I thought, how on earth did these get removed, they should not just fall out! Did someone remove them as a prank? Then I found fuses in the 8 position labelled “liftgate module logic” and the 12 position labelled “liftgate module,” and both are good/intact.

I was hoping someone who understands the system could help me out here. Do I need to put in a fuse where it says liftgate in the 5 position and a relay in the 16 position, and if so, does anyone know what size fuse, I cannot seem to find that information anywhere. Or do the liftgate module fuses suffice for proper operation? If anyone has a photo of their fusebox they could post it might be helpful. Thanks!

 

[Joseph Garcia]

You state that when you press the door button, the back lights flash, but when you do this, do you 'hear' anything in the door's lock/latch area, like a latch 'trying' to unlatch, or do you just have complete silence in that area?

 

[sbrekus]

You state that when you press the door button, the back lights flash, but when you do this, do you 'hear' anything in the door's lock/latch area, like a latch 'trying' to unlatch, or do you just have complete silence in that area?

I hear a very slight click noise in the door, barely audible, no hum or anything that sounds electronic

 

[Joseph Garcia]

I hear a very slight click noise in the door, barely audible, no hum or anything that sounds electronic

The click is significant, as that implies that the electric signal to release the latch is being received by the latch (probably). You may have to mechanically release the latch by drilling a small diameter hole in the middle lower portion of the inside of the door. There should be a round mark on the plastic face where this hole needs to be drilled. @Doubeleive may be able to better explain than I on specifically what you have to do, once you've drilled the hole to mechanically release the latch.

 

[Doubeleive]

I hear a very slight click noise in the door, barely audible, no hum or anything that sounds electronic

if you open it manually, while in the up position
does it...
1. close on it's own when you press the button
2. won't stay up and just closes on it's own
3. just stays open and doesn't do anything

 

[sbrekus]

if you open it manually, while in the up position
does it...
1. close on it's own when you press the button
2. won't stay up and just closes on it's own
3. just stays open and doesn't do anything

The click is significant, as that implies that the electric signal to release the latch is being received by the latch (probably). You may have to mechanically release the latch by drilling a small diameter hole in the middle lower portion of the inside of the door. There should be a round mark on the plastic face where this hole needs to be drilled. @Doubeleive may be able to better explain than I on specifically what you have to do, once you've drilled the hole to mechanically release the latch.

Thank you for the information. I don’t know, I cannot get it open. I did read about the dimple in the plastic and drilling a hole and so forth. The problem is somebody put some type of aftermarket or maybe even a GMC plastic thing in the back and it sticks up about 4 inches so you can’t get anything straight up in there to undo the latch. I’ve tried a bent
Allen wrench with no success. I will keep trying, but so far I cannot even get it open manually.

 

[Doubeleive]

The release is kinda far in there, straight back from the dimple, you need a long small screw driver to reach it

 

[sbrekus]

if you open it manually, while in the up position
does it...
1. close on it's own when you press the button
2. won't stay up and just closes on it's own
3. just stays open and doesn't do anything

OK, I finally got it open. When it’s open fully, it stays open. When I push the liftgate button on the door, it starts to close like normal and the back lights flash.

 

[sbrekus]

And now that I have gotten it open, we shut it fully using the front cabin button, and it close like normal. And then it opened like normal with the front button. Appears to be operating normally now. Something definitely happened and I’m not sure what it was. Does it sound like the latch has the problem? The electronics seem fine.

 

[sbrekus]

So it is closed again and not opening again. It was an act of God to use an allen wrench to get that latch open, great difficulty do it again. This large piece of plastic molding is right in the way of getting a direct screwdriver shot to that latch. Any idea how to remove it? I see no way to detach it. Thanks.

 

[Joseph Garcia]

Let's assume for the moment that something is causing the latch locking mechanism to stick/catch when it locks around the catch ring. Is there enough exposed for you to get some WD-40 on the contact point?

Have you tried pushing the door inward while holding the unlock button down to see if the pushing on the door allows it to unlatch?

 

[Doubeleive]

So it is closed again and not opening again. It was an act of God to use an allen wrench to get that latch open, great difficulty do it again. This large piece of plastic molding is right in the way of getting a direct screwdriver shot to that latch. Any idea how to remove it? I see no way to detach it. Thanks.

I guess my response from yesterday did not post
when you do get it open again I would remove whatever that thing is in the way until you can get it resolved
and at this point the options are troubleshoot it with a higher end bi-directional scanner or just opt to replace the lock actuator.
if you go that route just know that removing that hatch panel is a whole nother battle, clips are almost guaranteed to break, you will need a long pry tool because some of the clips are deep inside.
there is a couple youtube videos on "how-to" but not many for the k2 generation.
if it was a lift arm motor that would be a much easier solution.

 

[sbrekus]

Thank you for the information. Update: I was able to get it open again, and figured out how to remove the plastic storage compartment to easily open again with a screwdriver if it locks. It seems to intermittently work now from the electronic button up front and the outside of the liftgate, but not all the time. I have to assume at this point that the latch or actuator is intermittently sticking. I am going to lube it as best I can, and if it continues take it to a mechanic. I do not think I want to open it and mess with it based on how difficult it sounds. Thank you so much for the input, very much appreciated!