C240 (W203) TCU Removal
 

My transmission is still sporadically slipping after the o-rings and filter were replaced. I thought I would inspect the TCU to see if it came into contact with any oil (I learned about oil making its way via the connector way after the fact).

I have attached a photo showing it under the passenger kick panel.

I have removed a plastic nut (upper right). I can't seem to determine how to remove it with breaking anything.

Can someone impress with their prowess?

*Update - I uploaded another picture that is a little better. You can see the TCU through the two slits because its black. If I could hear from someone who has actually performed the procedure, that would be appreciated. Saying it just comes straight up after unbolting isn't helpful. There is very low clearance and its very difficult to see everything as the flooring material obstructs. Please refrain from any negative comments and maintain decorum. Thanks.

I haven't done it but if you have more pictures it would help. I can't tell anything from the photo. Back up and give a better overall view then move in.

Being an audio guy I can tell you that is the 45 degree floor base on the passenger side. I don't know where you TCU is, but that piece comes straight up after unbolting.

And again, more questions from those with incredibly low post counts.

E

The TCU is supposed to be under the passenger foot plate.

https://mbworld.org/forums/attachmen...1&d=1235857839

There are three nuts. One in the upper right and two at the bottom, left and right. You have to feel around for the ones at the bottom because the matting obstructs any view. There are on extremely tight and I don't have the right hardware to get it off.

I had that metal piece out when I was doing my stereo install. My RF 3sixty unit is now hiding under there. If memory serves- there are a total of 3 of those plastic nuts. After you get them off- it really does just pull right out.

Ohh, I didn't know that.

E

I got the nuts off but disconnecting the plugs is tough. I can't seem to get them off. I'm also limited by the length so I can' turn it around. Last thing I want to do is stretch the cords or put any tension on them. argh!

i just pulled mine out simple if anything the wire harness will just be held in by those metal clips and will pop free if you put to much tension and just pop back in when your done- but you should be able to flip the panel to the side or upside to get to the wire plugs

What idhibans said - you should be able to reach behind the panel and release the clips. I don't have pictures from when I removed mine, but it's damned close to R171 other than more room to work! :-)

I think you are being too timid with this thing. A bit more elbow grease required. I explained how to get this out to ichibans on his transmission CEL thread & in no time he had it all out.

Glyn,

You are correct. I just grabbed it and worked it free. The left pin was stubborn, the right one came off easily.

I just did this myself yesterday. Took out the whole passenger side carpet piece. What a pain! Anyways, there was a PUDDLE of oil around the bottom right side stud. Unbelievable. Looks like I will be replacing an o-ring. Oh yeah, I got pictures, but I just need to upload them from my phone.

Pete - sorry to hear that - Hope you caught it before damage to the TCU

Thanks, I hope so too. But I'm guessing it isn't damaged. I popped the board out of the case and there was no oil at all on that board. There was some oil on the plugs and a little bit on the contact area, but again, no oil in the actual module. I went to the dealership to get the replacement o-rings, turns out its a whole plug you have to buy now, but only like $13. I just have to put it on now. I'm curious, does anyone know if any transmission fluid seeps out or RUNS out when I go to replace those o-rings?

Looks like you caught it before damage - gr8 - TCUs are expensive & seldom in stock

Ask mleskovar re how much oil will leak - I see he contributed to this instruction on InstallUni.

http://www.installuniversity.com/mb/...ans_oring.html

I forget what my contribution was but I haven't replaced the O rings....it was evidently done under warranty on my car because when I became aware of the problem I asked....and was told "no outstanding TSBs" by different service writers. I've read posts where people say several ounces come out from both the plug and the wire loom. I also remember someone flushing the oil from the loom by using aerosol cleaner like MAF cleaner from the TCU end.

Okay, I'm bringing this thread back because I finally had the time to upload some pictures of replacing the o-rings. Or, I should say the plug housing it's self. Now, I started of course as everyone else has, I pulled back that section of carpet in the passenger side foot well. Then I removed the three plastic nuts holding that floor support plate down. I then pulled it off of the studs and laid it down as shown in the picture.
https://mbworld.org/forums/members/p...emoval-tcu.jpg

Here is a close up. It was two little bolts holding the TCU to that floor plate.
https://mbworld.org/forums/members/p...ose-up-tcu.jpg

After removing the TCU and floor plate, I actually removed the whole section of carpet out of the passenger side foot well area, yup, the whole thing comes out, from in front of the passenger seat, all the way up under the dash. After removing that, I realized how much ATF I had on the floor of the car underneath the carpet. It appeared to have wicked up the TCU wiring harness and drip off onto the floor rather than actually seep into the TCU itself. I know this because I opened up the TCU and check for oil, there was none. So, my next step was to buy the replacement o-rings for the plug at the transmission itself. Well, the dealership doesn't just sell the o-rings, they sell the whole housing that the harness plugs into, with the o-rings already attached. It was $13 if I remember correctly. Here is a picture of the old one (the one I took out that had failed) and the new one. It appears as though the faulty socket WAS a newer one with two o-rings, unlike the one pictured at the InstallUniversity website. Oh, when I replaced this, there was a slight dribble of ATF and that was it. However, I went to soak up the ATF so that I could install the new socket and it just keeps filling back up, so I just bopped it in there and hoped not to get too much fluid in the socket where the plug goes.
https://mbworld.org/forums/members/p...ug-o-rings.jpg

Thanks for the feedback Pete. You encouraged me to go and check my car but fortunately all is bone dry - a relief. You are fortunate with the TCU - FrankW was less lucky

I know I am reviving an old thread, but should I disconnect the battery to do this, or can I just have the car off to take care of it?

Glyn, can you please post a link to this thread?