2018 Suburban LT Liftgate problem

[OR VietVet]

My girl's landlord has a 2018 Suburban LT. The rear liftgate will open when you touch the inside of the rear handle but will not rise but can raise by hand and it stays up and when lifted all the way up and touch the button to close the liftgate, nothing happens but can push the liftgate down and it closes fine. The switch in the front overhead that controls the detent/severity of open and closing, says "Maximum" "3/4" and OFF, makes no difference on switch position whether it works or not. He also has a key fob control that does unlock it but again, it will not raise or lower by itself with the key fob. I looked at the fuse/relay panels under the hood and at each end of the dash and found nothing related. There is another fuse/relay panel at the very left rear behind a cover. Fuses are labeled as such: Liftgate.....Liftgate Module Logic and these 2 are 10 amp fuses and are good. There is a 30 amp larger fuse that is labeled for Liftgate Module and is good. There is a #8430 relay that is labeled just Liftgate and I found a matching relay to that and is in the engine compartment fuse/relay box and switched them with no help. When you lift the hatch or close it, you can hear the side struts winding up or down. I never do hear the lock actuator or motor working.

I looked on the internet and you tube but only found quick videos about if the rear hatch liftgate will not open at all or how to replace the side power struts. I decided to reach out here before I start removing covers and checking for power and ground.

Does anyone have info to share about this?

 

[intheburbs]

My Suburban exhibited the exact same behavior last month. Fob and button did nothing, was able to still manually open and close. My online research pointed to the lock/actuator.

Being hesitant to throw too much money/parts into it, I bought the crappy Chinese knockoff for $73, instead of the genuine Delco part for $250.

I just replaced it last weekend and it's back to working as it should. So if the knockoff fails, I'll then spend the money for the good Delco unit.

Install was pretty simple, some of the fasteners are a bit fragile, but it took less than an hour. 1A Auto had the best video.

Not the exact same part for a 2018, but I'd wager it's the correct fix.

 

[Doubeleive]

I thought those things had a motor in one of the lift struts? sounds like the lock actuator is working fine and the lift motor is not.

 

[Joseph Garcia]

Detach the lift struts and see if they are still pressurized.

 

[OR VietVet]

My Suburban exhibited the exact same behavior last month. Fob and button did nothing, was able to still manually open and close. My online research pointed to the lock/actuator.

Being hesitant to throw too much money/parts into it, I bought the crappy Chinese knockoff for $73, instead of the genuine Delco part for $250.

I just replaced it last weekend and it's back to working as it should. So if the knockoff fails, I'll then spend the money for the good Delco unit.

Install was pretty simple, some of the fasteners are a bit fragile, but it took less than an hour. 1A Auto had the best video.

Not the exact same part for a 2018, but I'd wager it's the correct fix.

Does the lock actuator trigger something in a motor that actually lifts and closes the liftgate? I would assume the lock actuator would do just that, lock and unlock. I am confused how that would then lift the liftgate? But, as you said about yours, the liftgate does unlock when you squeeze the button at the rear handle and does push away just a bit but then after that, everything is manual operation.

Can you post any links for the research you did? I look and all I see is parts replacement videos but nothing about diagnosing the problem. Thanks.

 

[OR VietVet]

I thought those things had a motor in one of the lift struts? sounds like the lock actuator is working fine and the lift motor is not.

Is the lift motor separate or in the strut(s)?

 

[Doubeleive]

Is the lift motor separate or in the strut(s)?

pretty sure it is in one the struts I think left side, should look thicker than the right side
has some kind of corkscrew operation inside, I don't think it is serviceable and has to be replaced.
post it up in the k2 section "what did you do to your k2xxx today", people have replaced it before

 

[OR VietVet]

Yea, I found out that the left side is the actual lift but still confused about the lock actuator assembly. It sounds like the lock actuator sends a signal to the lift and then that opens or closes. Do I have that right?

 

[Doubeleive]

Yea, I found out that the left side is the actual lift but still confused about the lock actuator assembly. It sounds like the lock actuator sends a signal to the lift and then that opens or closes. Do I have that right?

maybe..... this is one of those times a advanced scanner is needed to confirm the problem. the k2's use GDS2

 

[Doubeleive]

maybe it would be the motor if it only lifted part way and stopped, versus not working at all

 

[OR VietVet]

I am going to my friend's shop later today to have him plug in his scanner. He has a scanner that can do this.

@Doubeleive, the owner said he was experiencing an intermittent jerky motion and noises before the complete failure of the lift. Intermittent operation without the noises tells me an actuator problem but the noises make me think it is the lift struts. Maybe both should be done. Plenty of videos out there for the replacement procedures. I am going to question the owner with more detailed questions, after doing all this research. I do appreciate everyone's help too.

This guy is my girl's landlord and he was on the fence about me wrenching in the driveway when I asked for permission. Now he is completely on board since I work on his vehicle, his wife's vehicle, his son's vehicles and his golfing buddies vehicles. I actually have about a dozen vehicles in my neighborhood area that I have laid hands on. My neighbors are not afraid of the 6'4" tall and close to 300 lbs. grey hair and big beard deep voice Sasquatch lookin' guy in the neighborhood. They were standoffish at first. Even got some atta boys when I saw a homeless guy rummaging thru the trash cans at the curb of all the homes, looking for cans, and I ran the guy off and let him know to come back would be at his own peril. The street is a dead end and that helps make it easier to watch and we all watch. It is an upscale neighborhood but still see homeless a few blocks away on the main through road and they wonder around sometimes. All neighbors know I carry as well.

 

[gooffeyguy]

Thanks for explaining in that last paragraph, I know we were all wondering about it.

 

[OR VietVet]

Ha Ha, I get it. The jest is that I want to keep this guy happy, LANDLORD. Her rent is low for this area and the more he is happy, the lower the rent stays. Plus, he does pay me my going fee of $75 an hour for my labor. In this neighborhood, this landlord owns 6 homes. This dead end street is one of only two in the entire area. I like it back here.

 

[intheburbs]

Does the lock actuator trigger something in a motor that actually lifts and closes the liftgate? I would assume the lock actuator would do just that, lock and unlock. I am confused how that would then lift the liftgate? But, as you said about yours, the liftgate does unlock when you squeeze the button at the rear handle and does push away just a bit but then after that, everything is manual operation.

Can you post any links for the research you did? I look and all I see is parts replacement videos but nothing about diagnosing the problem. Thanks.

The lift/lower mechanism is the separate arm on the driver's side of the tailgate. Circled item pictured below. The struts are just your basic gas shocks. The arm does the actual lifting/closing.

I didn't save any of my searches, just went down a rabbit hole of Googling. The actuator/lock, the piece I replaced, must send some kind of signal to the lift motor to raise or lower the tailgate. Obviously, that wasn't happening. I do have a Tech 2, but I haven't played/learned with it much, and couldn't discern anything wrong digging into it.

So replacing the actuator/lock was an educated guess, hence my reluctance to spend $$$ on the Delco unit. But replacing it fixed the problem completely. Operates as good as new.

 

[OR VietVet]

The lift/lower mechanism is the separate arm on the driver's side of the tailgate. Circled item pictured below. The struts are just your basic gas shocks. The arm does the actual lifting/closing.

I didn't save any of my searches, just went down a rabbit hole of Googling. The actuator/lock, the piece I replaced, must send some kind of signal to the lift motor to raise or lower the tailgate. Obviously, that wasn't happening. I do have a Tech 2, but I haven't played/learned with it much, and couldn't discern anything wrong digging into it.

So replacing the actuator/lock was an educated guess, hence my reluctance to spend $$$ on the Delco unit. But replacing it fixed the problem completely. Operates as good as new.

I will look but on the 2018 Suburban, I don't remember seeing that arm. The two struts are beefier and as said earlier, I believe there is a cork screw effect in the driver's side, left strut. Maybe, just maybe, that lock actuator does still send the signal for the left strut to push up or pull down the liftgate. Thanks for the info and the pic.

 

[intheburbs]

I will look but on the 2018 Suburban, I don't remember seeing that arm. The two struts are beefier and as said earlier, I believe there is a cork screw effect in the driver's side, left strut. Maybe, just maybe, that lock actuator does still send the signal for the left strut to push up or pull down the liftgate. Thanks for the info and the pic.

Yup, different system. My bad.

 

[OR VietVet]

Attached scanner and there were no codes. Key in and turned to KOEO and the DIC showed the rear hatch open, because it was, so we knew the communication was there. Popped open the "umbilical" cord flexible conduit for all the pass thru wiring and that looked pristine. Ordered in new rear struts for the power liftgate. When they get here and if my girl is back from Texas, I will try to do a video of the struts replacement procedure. The ones I looked at on you tube are haphazard at best.

 

[Doubeleive]

Attached scanner and there were no codes. Key in and turned to KOEO and the DIC showed the rear hatch open, because it was, so we knew the communication was there. Popped open the "umbilical" cord flexible conduit for all the pass thru wiring and that looked pristine. Ordered in new rear struts for the power liftgate. When they get here and if my girl is back from Texas, I will try to do a video of the struts replacement procedure. The ones I looked at on you tube are haphazard at best.

the scanner did not have a option to command the hatch open/close?

 

[OR VietVet]

the scanner did not have a option to command the hatch open/close?

No it did not. I was looking over the shoulder of my friend that was doing this.

 

[OR VietVet]

Does anyone know if I have to have anything programmed/linked after these new strut assemblies are installed? I would assume not since the left one just gets a signal to move up or down but hell, I don't know. Thanks in advance.