so my soft close works perfectly on all doors, but the trunk won't "suck" shut.

You can hear the motor attempting to pull it down, but nothing happens. If you push down on the lid, it will latch.

Any ideas for why this would happen?

Im hoping its not a PSE pump problem, but rather a leak in the line to the trunk or something resettable.

Its worked perfectly fine until just now.

thanks

 

I'm keeping an eye on this thread, because I have the same problem on my 03 600. I have a warranty, but haven't found time to bring her in. It would be nice if there is something I could do without bringing her in. TIA!!

 

I've heard you can reset the system by pulling the fuse. I may do that.

Otherwise, I'll have to check the air lines.

I don't have time to go to the dealer either.

 

Most likely the locking pump and/or connections to pump have failed you, as the doors still work it is not the PSE. Pull back the Trunk lining and inspect all connections for leaks.

See Attachments

 

This is a pic of the Auto Trunk closing mechanism NOT the same issue as described above.

I just had this issue and I replaced my trunk Lock because it was leaking causing the soft close not to work. I did notice that on the new part there had been a sight modification and a part number change I hope it was for the better.

IT is a very easy DIY but there are two parts and they are both pretty expensive so make sure that you change the correct part.

The first part ( I don't know if your care has this ), is the retractable door handle. This pops out and in when you open and close the trunk, and also houses the button where you open the trunk from the outside, and the keylock. Cost is about $250.

The second ( about $250 ) part is the Latch assy. This is the part that I replaced. There is a big vacuum cylinder and another small cylinder attached to this part with a metal ball seal on the end. This is what is used to pull the vacuum for the soft closing. If it has a leak it will not soft close and will shut down the pump's output for that part.

After you replace the latch you will have to pull the PSE pump fuse located at the rear passenger seat for about a minute and reinsert it for the trunk softclose to resume functionality. IT normally will have shut down the circuit as a safety if there was a leak detected.

This is why you read post that people have reset their fuse and their system started working again. Be cautious of simply pulling the fuse as a final fix because you may find yourself needing a new PSE pump if the leak isn't corrected.

IT takes about 30 minutes to change the Latch out DIY.

The latch assy has about 7 part numbers and are VIN specific so remember to have your VIN when you go get the part. I was surprised that my local dealer stocked this item.. HMMMM I wonder why..

 

Thanks for the correction!

 

I have a similar problem, but a bit different.

Keyless go - touch the trunk latch and it should pop open, same as using the key. But instead, it just opens like 1/2 an inch and can be manually PULLED up with great effort.

Use the key - pops open like it should. Or, press the switch in driver's door , works the same way.

So it seems pump is ok, but something with keyless go prevents it from popping up same way it should.

Anyone else seen this?

 

Keyless go - touch the trunk latch and it should pop open, same as using the key. But instead, it just opens like 1/2 an inch and can be manually PULLED up with great effort.

--have you tried going into your settings and see if the Trunk Open Limiter is set to "OFF" ?

 

alright gentlemen,
I used the "pull fuse" trick and viola, victory is mine. If it happens again, i'll look for a more permanent solution, but at least now I won't have to practically jump on the trunk lid of my big dog newish benz.

 

this happens to my car but i reset the battery then sometimes one of the doors stop working (usually drivers) or one of the other three doors. If all doors are working then the trunk usually doesn't work. I reset the battery everything works for about two days.

 

You have a leak!

If you keep resetting you will end up needing a new PSE pump AND fixing the leak.


Please read my previous posts regarding pulling the fuses or unplugging the battery for reset... It is an indicator that there is something wrong and not meant to be a weekly routine.

 

very correct My06.

If mine acts up again, I'll look into a leak

 

i have run into the same problem, with my doors...and i just unhooked the battery for like 10-15min. and good as new

 

Have you ever figured out what went wrong with your trunk? I have the exact same problem. Do you think by removing the battery for a moment would help? Mine works if I lock and unlock all the doors many times.

 

I think it was generally a weak battery problem. I had to kind of force the lid up at one time, and I think that was what did it.

Since MB roadside assistance swapped my battery under warranty, I've had nary an issue.

 

I have the trunk soft close failure- but I don't see "PSE pump" listed on the fuse chart. I do see f39/f73 for the "remote closing and locking trunk lid". what is the magic fuse?

 

the problem may also be the rear can, it controls the rear taillights and the trunk including the soft close. its under the rear seat on the passenger side, in my case it got wet and so i cleaned off the connections and everything worked fine so i reccomend checking that computer before making any major purchases. if anyone is curious its located under the fuse box under the rear seat its actually attached on the bottom, i disconnected it on a unplugged battery and just cleaned the connections because they had a little water build up and problem solved. hope this helped

 

what's a 'rear can'? And how can you get to it if it's under the fixed fuses under the rear seat?

 

CAN is for Controller Area Network. Have you driven your car through deep water?

 

No, and I see no moisture looking at/below fuses under rear seat

 

My dealer wants $380 for the latch!!!

 

I have the same issue on my SL55 with the trunk. The trunk just all of sudden will not soft close. I have to somewhat force it to close properly. When I open it, it doe snot come up on its own as some people are explaining. Should it? What fuse can I reset for this to try it out?

 

As mentioned already, do not use the fuse as a fix. It should only serve as a debugging tool while you are figuring out what is really wrong. I have the same problem on my SL55 and am in a process of fixing it. In my case it happens to be the trunk locking mechanism that cracked in the most unusual spot and is leaking, causing the pump to cut off air to that particular area after two failures. I would be more than happy to help you figure this out.

Assuming the only thing that is no longer working is the trunk while the rest of the system is functional and you have just reset the fuse:
1. Remove the trunk lid liner
2. Remove the lock assembly
3. Remove the air hose shown in IMG_0052
4. Simulate locking by engaging the lock hook
5. When you hear the pump running put your finger over the hose, if the pump stops you are lucky and you only have to deal with the locking mechanism. If the pump doesn't stop, listen for air leaks along the line you are holding. If you can't find the leak, I can't help you. If you don't hear the pump, then your pump is probably bad and I can't help you.

Assuming you make the pump stop by covering the line described earlier by either not having a leak or fixing it.
1. Buy new locking assembly and replace it
2. Reconnect the line and listen for leaks at the locking assembly, fix if possible and put it back in

 

My door unlock/lock has failed as has the soft/close and trunk. I am going to replace my PSE pump, but how do i know i dont have a leak somewhere that will damage the new pump? Any help would be appreciated.

 

i have the same problem !! removed the battery for 15 min.. and wow it worked again .
then locked the car ( from inside while the car was running) and unlocked the car again also from inside and bam back to not working... my mechanic said its prob something in your locking system ! not sure i still have to work on it and see
and if i wanna pull the fuse which one is it?
thanks