How Replace Transmission Control Unit (TCU) module/connector

Have found a bounty of info and helpful forum members with info Re. trans fluid change/flush, but haven't found much info on this TCU connector.

I have heard/read about some other job to be done at same time as dropping the transmission pan. Something about replacing badly designed original connector with an improved connector, better O rings, to prevent ATF from corrupting electical components of transmission.

Where is this connector located on a 722.623 on a year 2000 CLK 430 Cabriolet? Where can I find a How To on this job? Photos would be nice.

I have a link to the part:
http://www.autohausaz.com/search/pro...partnumber=203 540 02 53

 

It's the o-ring that usually goes bad The arrow points to the connector.

 

Thanks

 

A few questions Re. CLK (W208):

1. Seems E series TCU (trans control unit) is under the hood in a passenger side box at firewall. If ATF wicks to this unit on E series, then need to check TCU in CLK (W208) for similar ATF contamination. This similar box on the CLK (W208) is where I plug in my multiplexer to read, clear, and print codes/reports. Question: Where is TCU on W208 located ?

2. Regarding the W208 only, not any other series, is the following correct regarding the New AT Plug Adapter for a W208, and if not, then would someone kindly correct it, making reference to A,B, C, etc?

Regarding the W208 only:
A. There are 4 parts involved in this issue: 1. Harness plug; 2. Old Plug Adapter; 3. New Plug Adapter; 4. TCU (trans. control unit).

B. The male Harness plug has a single red O-ring and is a different part from the AT Plug Adapter.

C. The Old Plug Adapter has a single O-ring and this is where the typical leak originates.

D. The New Plug Adapter has 2 O-rings and replaces the Old AT Plug Adapter.

E. The typical leak problem originates in the Old Plug Adapter--the fluid seeping past the single O-ring in the Old Plug Adapter; then migrating past the red O-ring in the Harness Plug; then migrating upward in the wiring loom; then contaminating the Transmission Control Unit.

Thanks

 

I just bought and replaced this Tranmission Plug connector at the dealership for 10 bucks!!! I replaced it 2 weeks ago because it was dripping ATF fluid. I had been chasing the drip for a while and even the dealership said it was a loose trans line and tightened it. That obviously did not fix the problem so I researched and found that the plug might be the culprit and I was right!!!!!!!

I took out the plug and ATF Fluid was all over it. I bought electrical cleaner and used almost half the bottle to make sure that the wires were absolutely as clean as it could be. I replaced the plug with the new and placed the aluminum cover back over it and I have yet to leak a single drop! Oh one more thing on that cover, you only need to remove that one bolt on the bottom. The second bolt does not need to be removed at all, the cover just slides under that 2nd bolt so it should be way easier to remove now that I know about it.

My transmission seems to shift a little better but that could all be in my mind. At least I know that it will not fry anything anymore and I am done with adding 18 dollar trans fluid every 3 months!

Greg

 

1. You are correct the TCU is supposed to be located on the passenger side firewall inside a plastic box. There should be a couple cards in their but I am unsure exactly which one is the TCU.

2. A: All I bought at the dealership was number 3, the trans plug connector (10 bucks at the dealership!!. This is all you should need unless you know for sure that the main harness has wicked bad enough to warrant a replacement at 300 bucks!!

B: you are correct. No need to replace the male harness and yes the male has one red o-ring and the female plug that needs to be replaced has to red o-rings. (The new one will have black o-rings)

C and D: Incorrect..they bought have 2 O-rings. The plug has been redesigned and better o-rings have been replaced as well.

E: Hmmm..the way I was described was that the old female plug was designed incorrectly thereby allowing oil to seep past both of its orings thereby allowing oil to seep into the male plug and into the wiring. I believe this to be the case since my leaking stopped and I only replaced the female plug.

You will first grab the plug by the tab and turn in counterclockwise. This will disconnect the male plug and allow you to pull out the male plug. You will then need a 7mm socket to get the female plug out. The bolt/screw is located in the middle of the plug, hopefully you can see it in the pic. My o-ring stayed inside so I had to reach inside to get the 2nd o-ring out. I then sprayed electrical cleaner in there just to make sure that it would be clean when re-installed. I also sprayed the male plug VERY generously so that I would not have any issues with wicking.

OH YEAH...I just remembered! There is an oxygen sensor that is located closest to the front of the car that will be in the way. I removed this sensor and tucked it away temporarily and it made the job a heck of alot easier!!

Hope this help!!

PICS ADDED:



Greg

 

GREG is DA MAN!

or Der MANN !

 

\


DAMN YOU ARE QUICK ON THE DRAW..only 3 minutes after I post!!

Ummm...I'm a DUMA** its actually 12 minutes after my post!! I will crawl back in my cave now LOL.

 

Damn Greg, you are on a freekin roll. I'm just gonna sit back and watch the magic happen....

 

LMAO it may seem that way but there is a reason that I know these things right now. MY CARS FALLING APART AT THE SEAMS!! So thats why I am able to help others out.

Actually the cars been pretty damn good to me and I expect some of these things to go bad after being so close to 140K miles now. Hopefully it gets me to 250K like some of the CLK's in Germany!!

Greg

 

Hey,
A great on point response.
You cleared up all of the obscurity,
and your photos of the AT Plug Adapter are a great help.
Thank you very much.

 

No prob!!

 

Thanks for the info. In doing this job on my '02 CL500, I find an o-ring on the male insert as you mentioned. Were you able to get a replacement o-ring from MB. I just called the dealer and the guy said he could find no o-ring on it. If you were able to get it from MB, would you happen to have the part #?

 

The two CL part numbers are the same as a CLK430 - 0269974148 ($2) and 0269974048 ($8) (those are the updated part numbers)

 

Thanks! I thought the 2 o-rings for the connector weren't available.

 

Marcus, I'm confused.

I am looking for the O ring that fits onto the male plug from the harness that goes into the new A/T plug adapter. I thought the male plug only had one O ring.

I know that the old/bad A/T plug adapter has two O rings, and that the new replacement A/T plug adapter also has two O rings,

but, the male plug from the harness that goes into the new A/T plug adapter, looks like it has only one big O ring, not two.

Questions:

1. Are the O rings you are talking about, for the A/T plug adapter, or for the male plug from the wiring harness?

2. If for the male plug from the wiring harness, then does the male plug from the wiring harness also have 2 O rings ?

I uploaded a picture of the male plug from the harness to see if we are talking about the same device.

Thanks

 

Pancho,

You are correct about the harness plug only having one O-ring. Its only the replaceable adapter with the big white TAB that has 2 O-rings.

BUT......Now you have me thinking about the job I did because I did not replace the O-ring on the male harness plug and now I think that I should have just as a precaution and edspecially because I already had it unplugged!!

I am not leaking ATF fluid anymore since I replaced the adapter but if I ever have to do it again I will definitely buy another O-ring for that harness plug.

Greg

 

Greg,

From my survey of the forums, I have gleaned the following Re. the harness plug O ring.

1. I can't find any part number for that O-ring.
2. At one time the O-ring was available from dealerships.
3. The O-ring is no longer available from dealerships.
4. Reports, including yours, that the plug assembly stops leaking after the new A/T plug adapter is installed.

I wish I could find the part number and the O-ring, but it seems like it might not be necessary to replace it in order to stop the leaking. The A/T adapter seems to do the job, I hope. To paraphrase F. Gump, that's all I have to say about that (I hope.).

I do need some help Re. seating the new A/T plug adapter. Need to know if the larger O-ring seats totally within the trans housing and is not visible, or if it rests (abuts) between the adapter and the trans housing, remaining visible. My vehicle is staying on the jack stands until I figure this one out. Here's a link to a posting I made Re. this issue.:

https://mbworld.org/forums/clk-class...722-623-a.html

 

I left a response on the link you posted.

 

i see the plug does it come off?

 

thanks ahead of time

 

Sorry about following up so late.

On Feb. 28 did the transmission flush and installed new pan filter, gasket, magnet, drain plug washer, & Trans. adapter plug. Did not get suckered into buying the $29/Qt. MB transmission fluid. Used Valvoline MaxLife ATF, $3.67 /Qt. at Walmart.

Search the forum for the MB Tech. Service Bulletin that recommends Valvoline as an alternative fluid, and also for the compatibility verification letter from a president of Valvoline. The TSB also lists a Shell alternative. MB does not refine oil. It buys fluid from a producer, then re-brands it with the MB logo, and sells it at a one thousand per cent profit above regular retail price. Thieves.

I used about 17 Qts. because I flushed an extra 2 or 3 Qts. through--until it started coming our pink from the cooler line. You can do this at $3.86/Qt.

Again, thanks to everyone for the help, and, again, sorry for the late follow up.

 

very imformative

 

I have the same leak from the connector and when I attempted to unscrew the 7mm bolt it would not release. So after a few hours and chipping away the connnector so that it could come out with the valve body i now have to replace the conductor plate. My question is about the fluid i am about to use redline synthetic has any one had or heard of anyone using this? How did it work? Should i stick to the valvoline alternative fluid?

 

Unless you can find documentation stating that the fluid meets the MB specs. and is a direct replacement, why gamble ? When you reinstall the plug, be very careful not to over tighten that small bolt.

Here are some helpful links:

https://mbworld.org/forums/clk-class...oler-line.html

https://mbworld.org/forums/clk-class...722-623-a.html

http://www.benzworld.org/forums/w210...r-plate-6.html

See posting #61 in this topic:
http://www.benzworld.org/forums/w210...-tranny-7.html

Best of luck.