Pseudo Nim

SoI am debugging a REALLY weird issue. My trunk will not close all the way - it gets stuck halfway, then bounces back up.

Check out this video - but especially pay attention to the last few seconds:
Here's what happens:
- every single time, when closing from full open, it will get stuck about 70% of the way down, as if something mechanically catches it, then it re-opens
- I tested the resistance on the pinch sensor strips - and shorted them with a 3.9 kOhm resistor for extra testing - no change, the sensor strips are functioning correctly
- I recalibrated the unit with Star, that did not help
- If I manually use the actuations in Star, it will still get stuck
- sometimes in VERY hot weather, when the hatch is quite hot to touch, sometimes it will then just close normally without any problems.

Here is where it gets REALLY odd, though. If I STOP the closing at around halfway, and THEN continue it, it WILL close completely. As well, if I set the door limiter function (i.e. it will not open completely to begin with), then it WILL close completely.

Would anyone have any idea what may be causing this? The only thing I didn't do yet, as was suggested by @Tsumi in another thread, is refill the hydraulic oil - it's on my list of things to do; but I am strongly inclined to think that it wouldn't resolve the issue, as otherwise the door functions as expected (and once again, if it's only opened halfway, then it will close fine).

Tsumi

What finally ended up resolving that for me is doing a full reprogram of the module. I'm not sure which it was but it was one of the options that said use in the case of replacing the module, or something similar. Ideally do it while facing up an incline as that seems to be the most difficult position to close (I think, might be the other way around).

Pseudo Nim

Yep there are two options in that menu - use data from existing module or start new “in case old module is unavailable”. Would you happen to remember which one you used?

Tsumi

Start new in case old module is not available.

ArcticR320

I have exactly the same behaviour on my R320. 70% of the way down, then re-opens. Have flushed and refilled the hydraulic oil which didn't resolve the issue, but nevertheless did make the door move a bit smoother. Will definitely try the reprogramming during the weekend. Thanks to Tsumi for the info🤝

Tsumi

Yeah, after the reprogramming, it still does that occassionally. Now it's like 1 out of 10 times it will do that instead of every time.

Pseudo Nim

I am sad to report reprogramming did nothing for me.

I went to Initial Startup > reprogram module (manual entry of settings), manually picked the two "not fitted" options, it wrote the coding, then made me do the re-calibration of the tailgate, and unfortunately, after all was done, there was no change at all, rats.

Tsumi

Damn, that's unfortunate.

I have noticed that the pump has been getting weaker at opening the liftgate lately. It might be a symptom of pump failure.

ArcticR320

Reprogramming made no change on my car either.
What seems to be some sort of remedy is to set the intermediate position (garage position) to 105. Not ideal, but at least I don't have do close the door manually,

Pseudo Nim

So I talked to another R class owner who spent some time debugging this with his mechanic. Their conclusion seems to be that the shocks have gotten weak, and when the trunk lid closes, the closing speed sensor panics because it thinks it’s closing too fast, so it catches it and opens it - which is why stopping it halfway and continuing seems to work.

I’m not entirely sold on the idea as the “brake” spot seems to be EXACTLY in the same spot every time, but I could see the shocks being at fault, and undoing the headliner isn’t something I’d be excited to do …

V.V

Well, same thing for me.
I have noticed 1-2 times occasionally but I thing it will become permanent.
I have spoken to my mechanic. If it was about fluids or the pump we would have a problem opening the trunk. Since it happens when it closes sth causes a little problem to the sensor about speed or something else. On the one side is the hydraulic system on the other side is just a usual gas strut. I will have this one checked because it might make an abnormal movement during closing that the sensor thinks sth is wrong.