Recently the power liftgate on our 09 GL550 started to act up, and it wouldn't close after pushing the button. From the open position, it would close about 2 inches, then beep and stop.

Took it to the dealership, and they replaced the entire trunk closing liftgate, but the issue was still there. They did more research and found a service bulletin from 2008 which states a wire pinching may be the cause.

Of course, this pinching wire is located in an awkward place and the the entire headliner needs to be dropped to re-route the wire.

Has anyone had to do this before? Or has anyone had to drop the headliner? My concern on dropping the headliner is not only damage and staining, but the possibility of having rattling and a sagging headliner.

 

If it's under warranty, why not get it fixed right? Any damage done will be covered by the dealer.

 

Yes, we had that occur on our 09' GL 550 2 months into ownership. It was a wire that was not crimped tight enough to make full contact. Its been 2 years now and problem solved. i think in the process they "reprogrammed" a computer module/board it as well.

 

This is a normal occurrence. If you walk away with the key after pushing the close button, it will come down a few inches and stop. You need to stay there with the key (for the keyless go) until the tailgate is completely closed.

 

because i've had headliners removed before and its never going to be the same after its been removed. you will get some sagging, rattles and staining.

wanted to avoid that, but it looks like i won't be able to.

 

thanks. glad to hear someone else had a similar issue and it was fixed.

 

that's not the issue. i could be standing right under the tailgate and it would still do it. at times it will bounce up and down 4-5 times before closing.

pateljb posted, and had the same issue i have at the moment.

 

I am having same problem on our brand new 2011 350 Bluetec.
Already had the latching mechanism replaced but it still happens but only sometimes now.
It looks like keyless go does not see the key being there when closing or opening doors.
I have both sets of keys with me but still same result.
Option number too is that the doors close really hard hitting the back of the car.

At this point I am monitoring the situation.

 

well crap. this may be the issue with my '09 GL550. It intermittently works, but generally it's a 50/50 crapshoot whether it'll work or not.

 

STAR scan pulled up the "pinch sensor strip" code but nothing else. Today, I noticed a plastic trim piece (black) wasn't seated all the way. I popped it fully into place, and now the liftgate is closing most of the time. Sometimes I have to press the button twice, and once I had to throw my keys inside the car. Now seeing if the problem will sort itself out; fingers crossed!

All that's left then is a carpet cleaning for the interior and she'll be good as new

 

liftgate acting up again. I'm DYING to find this "anti-pinch" strip sensor thing....

 

GL550 was in for a Service B but they didn't have time to fully investigate the mysterious liftgate issue. Until it goes back in again next week, I thought I'd do some research. It seems to me that there's an intermittent switch, which is #12 in the diagram here:

http://workshop-manuals.com/mercedes...ce_and_repair/

It's a $90 part so (even with a couple hours labor) it isn't the end of the world by any means. http://www.genuinemercedesparts.com/...Y4LWdhcw%3D%3D

I considered taking things apart myself but while this would be straightforward for an experienced Mercedes mechanic, it's definitely above my pay grade. I have no doubt I can get to the sensor...it's getting things back together that's questionable!!

 

If it is starting to close, then opening again, yes it sounds like the pinch or force sensing system is triggering it to stop.

The hatch closes on a rubber strip, and it knows if something (fingers for example) are being pinched, then it reopens again. Same as how your garage door works.

These systems use one of two ways of knowing. There is too much force needed to shut the hatch (so it must be obstructed by something), or there is a sensor on the door that touches something and it reopens.

One way I have seen it done is to have a rubber tube with two wires in it. The rubber tube runs around the bottom edge of the door. If the door hits something the tube collapses and wires touch. Then the door opens again.

I suspect the rubber weatherstrip may have a sensing tube inside it, or maybe it's part of the bottom edge of the door.

I'd start finding parts diagrams for that door and see if you can identify the part. It probably isn't too expensive ($100?) and you can swap it and see if it fixes the problem.

With the code you are getting, it strongly leans towards this sensor being damaged somehow and it's falsely triggering the "oops, something is pinched, open up the door again" system.

Your windows use a similar system. Stick a piece of wood in and close the window, it will go right back down again when the glass hits the wood.

Edit:I did some research and it appears it uses a sensor on the lifting mechanism, not a door-edge (rubber tube with wires as I described above) type of sensor.


Something notices that the door is hard to shut, and opens it again, since it thinks there is an obstruction.

There is a sensor someplace you need to find. It's probably called an obstruction sensor or something like that. It is part of the lifting mechanism (pump, lift struts, etc.)

They probably swapped the sensor over when they replaced your lifting mechanism and it is still bad.

The only other thing it can be is worn out lift struts which are harder to move, causing the system to trigger because it is hard to close the hatch. But if yours were replaced, it's the sensor then for sure.

 

By the way, here is an article that references the "right obstruction sensor" and how to get to it. I suspect there is a left one too, but not sure.

https://www.fcpeuro.com/blog/posts/m...-w164-and-x164

Here is his quote:
"I opened the tailgate and loosened the right obstruction sensor. This is the black plastic cover around the tail lamp that has a wire running behind it."

 

Have the same issue on my 2009 GL320. It disappeared for a while after I set the limit to open about 3 inches below maximum opening height. But now it is back again. I also suspect it has to do with a sensor on the lifting mechanism. If I put pressure on the door to close it will close in 1 motion. If not it will go up and down few times.

 

that actually sounds like overly stiff struts. never thought of that, but sounds awesome if that's the issue as it's a simple fix. there's actually a tech with my liftgate apart as we speak, looking for possible wiring issues.

 

tech says my battery is on the weak side; wiring all checks out and the liftgate closing problem disappears when the car's on a booster maintaining a higher voltage. That makes sense; the liftgate ALWAYS is able to close after a 15-20min drive and the battery is topped off, but after 5min it starts to weaken.

So I paid an arm and a leg for both batteries and get to install them tonight.

I'm wondering if the gas struts are stiffer than "normal". If so, they're placing more strain on the closing system than necessary. New gas struts are $200. Each. Sigh.

 

I checked my Battery by pressing R-button 3-times and it says 11.9V on the display. Then I opened up the cover under the passenger seat and the neg terminal is all corroded. Tried to clean it up and remove the clamp. But the whole terminal starts moving. I think my battery is toast. Maybe that shows the trouble with the lift mechanism. Thinking of installing AGM battery instead of OEM and see if problem goes away.

 

I installed new batteries. Overall it wasn't that bad a job; watched a couple YouTube tutorials and my wife's very thin hands made it possible. It worked...for 10 minutes. I'm ordering new struts today; if that doesn't do it, it means a wiring connection is intermittent.

 

oh, and I checked my car's voltage by pressing the R button three times; it was 12.7 after I shut off the car and dropped to 12.4. Gate closes today if I get in the car and press the start button to turn on accessories.

This is my first Mercedes with KeylessGo; does the system require the key to be in a certain place or the car's accessories turned on, for the auto-closing liftgate? Seems strange if true and irritating as hell. Our old GL450 didn't have Keyless Go but the liftgate closed when you pushed the button. Very simple and worked fine.

 

new struts installed. Bolts take a T45 torx and require blue loctite. From the force needed to take them off, I guessed the torque needed was 35lb/ft. Upside - pretty easy with a helper and it ended up being a great bonding experience with my wife, who has discovered she really likes wrenching on cars, even if her passion for them is limited.

Downside - didn't change a damned thing.

So after $750, new batteries and new struts, the liftgate still opens 100% of the time, and only closes when the car has been running for at least 10min, or at random times when it feels like it. I tried putting a second battery on the jumper terminals. No joy.

So it's either wiring, or programming. I am determined to figure this damned thing out.

 

have you checked the handle to make sure it isn't dirty and getting stuck...it was the issue for me...took it apart cleaned it up problem solved

 

Yes, I had the handle getting stuck too. I actually took the hatch apart to lubricate the spring in the handle, but turns out the handle spring is more exposed to the outside of the door than the inside. Now if it sticks I just spray some lubricant at the edges of the handle where the spring is. Look at the handle.

As a next step, I would get a DAS test done to see if your truck is reporting any codes (stuck handle, pressure sensor problems, etc.) before you start changing any further parts.

I think you are through the hard/expensive stuff now, so don't give up. It is likely just a switch/sensor/etc.

 

Seems like you are dealing with the same issue as we have on my wives 2011 GL450. Lift gate only goes down when car is running.

I love to learn what the final solution is to your predicament.

Br,
Hans Jan