Limp mode, 722.9 connector and P0748
 

My vehicle is a 2009 Mercedes E350 with 121,000 miles with the 722.9 transmission. Three weeks ago the car went into limp mode (or basically started in 2nd gear and wouldn't shift). I read the codes with mt Autel MD805 and got the 0748 code on the transmission and a dozen low voltage codes or voltage too low to read etc.
Next morning car would barely start. I checked the battery and it was less than 11.8 volts on full charge and was about 6 years old so I replaced the battery. I read and erased all of the codes and let the car sit overnight. When I drove it the next morning the car shifted and drove fine, no more P0748 or low voltage codes and no codes in the transmission module.
Then, 4 weeks later the car went into limp mode again and I got P0748 again and also a Brake Light Switch code, and the ESP light was on. I cleared the codes but they both came back immediately. Now, I don't get the P0748 code anymore, it just says that the MD805 can't communicate with the transmission module. I was told by a local indy to raise the car to check the connector. It is full of oil.
Here is my question (and of course I will gladly welcome any help), I have changed the 13 pin connector a dozen times on the W210's I have had through the years, but this connector is different. It doesn't appear to be removable. Can I just change o-rings or do I have to get another conductor plate?
Any help will be appreciated. I have attached a pic of the connector.https://cimg0.ibsrv.net/gimg/www.mbw...94ff0120f5.jpg

That pictured connector is fixed with the conductor plate. You could take down the conductor plate and change out the o-ring - although MB does not list a separate part number for the o-ring that I can see in EPC. I would imagine you could source an equivalent.

Thank you. That answers the question of whether or not I need to remove the conductor plate. I am having trouble finding part numbers for the three O-rings. EPC shows part number for the top 2 labeled 4d but no part number that I can see for 4c. I haven't removed the conductor plate yet because I want to make sure I check everything first. Also, since I wasn't communicating with the transmission module at all, I used some electronics cleaner on both ends of the connector and let it sit overnight. I reconnected the cable and tried to read the codes and I got this message. "the internal check of component Y3/8Y2 (K1 clutch control solenoid valve (VGS)) has failed" and fault code 0748. So I guess the cleaning helped open the communications, but something else is preventing it from checking the Y3/8Y2 component.

Any ideas for what to check next?

https://cimg6.ibsrv.net/gimg/www.mbw...9d09543139.jpg

I might be misunderstanding your post - but I think the communication is working and it is reporting the error - Y3/8Y2 failed. Once you take down the conductor plate - it's easy to change out the Y3/8Y2 component. I've attached a diagram with the components called out.

Actually I am wodering if the solenoid Y3/8Y2 is bad or is the conductor plate bad?

In my case I had error that pointed to the Y3/8n4 - Transmission Control Module failure and the trans would randomly go into limp home mode. It was quite the process to buy a replacement ( sign a disclaimer, etc.), and have it SCN coded. The nice part is that you'll be upgraded to the VGS3 version.

So in your case the conductor plate was bad, is that right? I am wondering if my problem is the solenoid or the conductor plate. Can anyone tell me how to diagnose this? Also, if I replace just a solenoid, do I have to re-program the conductor plate ?

Yes - since the TCM couldn't be changed out separately, I had to change out the entire conductor plate. A decent code reader should be able to pull the failure code - I think that is the only way to diagnose and determine the fault. If it is a Y3/8Y2 solenoid failure - you will not need to SCN code or re-program the conductor plate. Just replace the solenoid valve.

Thank you KJB55, I will know soon enough. I will start taking the valve body out tomorrow. One last question (at least for now), there are three O-Rings on the electrical connector, I have a part number for the two at the top, but there is a "square" o-ring at the bottom that I can't find a part number for. Do you know how I can get that part number? It is pointed out in the attached picture.
https://cimg3.ibsrv.net/gimg/www.mbw...fc44ec169a.jpg

I searched EPC Net every which way and can't locate that 4C o-ring. Might want to try www.circuitboardmedics.com as they are a rebuilder of the conductor plate for speed sensors and might know or be able to supply it.

I have a 2007 C230 with the 722.9 transmission and have a P2767 code (Input/Turbine speed sensor "B"circuit No signal). I actually have another transmission (and conductor plate). Question is can I swap the conductor plate from one to the other or will that require programming and I'd be better off to just get the original conductor plate with the P2767 code repaired?

Shift solenoids really do not fail in the 722.9 transmissions. It's always the conductor plate and you can not take a used one from one vehicle and install it in another one. Well, you can but you will require special hardware/software to virginize the module and then program/scn code it to the other vehicle.

How should I proceed
 

Thank you,MBENZTECH . So I have the valve body back on the car but I haven't put the pan on yet. I connected the valve body to the transmission connector and read the codes without starting the engine (key in position 2) and Code 0748 came up . I cleared the transmission module codes and turned the car off. Turned it back to position 2 and the code came back. How should I proceed?
This is the actual error code message from the transmission module code scan:
"The internal electrical check of component Y3/8y2 (K1 clutch control solenoid valve (VGS)) has failed"