WIS 27.19 Transmission – Electrical System
W220 Transmission Conductor Plate Issues
If the transmission is a 722.9 seven speed, the valve bodies and TCM are usually junk and often have to be replaced. The general opinion is that the 722.6 five speed has not had as many problems with the conductor plate as the 722.9.
It is recommended that you check the conductor plate. Most often, that is the cause of rough/strange shifting. Enthusiasts have reported that their cars would just go into neutral while driving at highway speeds with faulty conductor plates.
How to open a 722.6 TCM Refer to: http://www.benzworld.org/forums/w220-s-class/1681972-how-do-you-open-tcm.html
Q. Can anyone please tell me how to open the TCM that I have removed from my 2001 S430? I want to see if there is any corrosion and give it a clean with electrical contact cleaner as recommended by some of the more experienced guys on this forum. Is there a method of pulling it out of the black plastic sleeve?
A. The circuit board is sandwiched between the two halves of the case. It is not easy to damage even if you break the plastic case/cover. It's actually very easy to open, you'll need 2 flat screw drivers one for each side. There are clips on each side that need to be released. I've opened mine with ease but come to find out my TCM was corroded so I ended buying another one from a salvage yard for $200 and thank goodness its been working great otherwise I'd have had to pay $1300 for a new one.