CaptainKirk2016

Trunk Assist stopped working - we've never heard this before. I had the dealer fix the wiring harness issue three years ago before I had a problem and I just checked the job they did back then and the harness going up the driver side arm is not the issue in this case. Third brake light is functioning and the locking mechanism is locking and unlocking just fine - the lid just doesn't go up or get pulled down. I can open/close it manually and the lock will engage, but that is all.

Anybody expereincethis exact set of circumstances? Would appreciate it if someone would share the fix if it is know.

Thanks in advance!

lost27

I just had this same issue on my w219 and ended up having to replace both the trunk assist motor and the controller. I found a used motor on amazon and a used controller on eBay to offset some of the cost. All the work was done at Eurocharged Austin.

CaptainKirk2016

First of all, THANK YOU for responding. I have been amazed at the lack of community in the MB circle in contrast to my participation in the BMW and Ford/GMC diesel forums. I beleive this may be the very first response I've gotten.

That said, can you please just confirm that your latch was working properly once you manually lowered the lid and if all of the lights, including the third brake light were functioning?

rustybear3

Checking your posts, I see you've gotten various and sundry responses to your posts and threads. So you have gotten feedback. Responses are based on the popularity of the thread and relevance. My goodness, you're a newbie in terms of posting...only 13 in 2 years....give it time!

CaptainKirk2016

I think if you look at the responses, weren't all of those tied to a political thread around gun violence? I may have sites confused, but I can say there are a ton of unanswered threads here and maybe it's just because I'm picking the most uncommon, uninteresting topics to search. Now I'm curious - I'm going to do a search to see!

lost27

I wouldn't say the latch was working properly. My symptom was that when I unlocked the trunk, it would pop open a little and I'd have to force the trunk by hand open. When I pressed the auto-close button, it would make a buzzing noise but I'd have to force the trunk down to the latch at which point the soft close took over and closed the trunk.

The trunk close button light was working, as was the third brake light. No issuse reported with the wiring.

CaptainKirk2016

Ok. This is exactly my condition. Hmm. Might take a chance on an ECM from eBay. Dealer says it could also be the motor or the position sensor. Thanks again for the feedback.

lost27

FYI here is a link to the exact part on Amazon for the trunk motor: I paid about $165 for the motor and ~$45 or so for an eBay controller. It was around $600 in labor to get it all installed. For reference, the motor and controller from the dealer were over $900.

CaptainKirk2016

I bought a unit off of eBay for $127 that is the motor and ECM combined. Figured it was less than one hour of labor at the MB dealer so having two of the same year CLS' in my garage, why not. Thanks for the help!

lost27

I think it was a little more than an hour of labor at my Indy because they had to disassemble the rear deck and trunk to get to the motor and replace it.

vvrjrlaw

Try the controller module first. Mine did exactly the same thing and I replaced the controller module and back in business. Did an autopsy on the “ dead” unit and there were small burn marks on the board near some of the surface mount components. Itstcooks. That and the audio gateway because they used a cheesy Chinese fan to cool it and it seizes and everything shuts down.