GangStar

Hey guys, I've been a little scattered trying to figure this issue out, I've worn my fingers out trying to google search and talk to TCM repair shops. I would love some input.

Car-08 C300s 193K mi , Well maintained.
Scanner-Snap On Apollo D8
Routine Trans fluid and filter change 3k miles ago. Old fluid didn't look bad.
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Concern: About 2 weeks ago I jumped in and immediately got a CEL light with these codes:
Engine
0688-This Fault can be ignored
Transmission
P2759-The internal electrical check of component Y3/8y8 (Torque converter lockup clutch control solenoid valve (VGS)) has failed REad and observe repair information
***The car performed perfectly normal***
I would clear the codes, and drive around running errands let the car sit a few hours and the codes immediately returned on start up...this went on for about a week, then...
The CEL light disappeared. Hmmm

2 weeks go by.....

Everything is normal, a 20 mile drive first thing in the morning. Park for a couple hours, select drive and THUD, I thendrive about 1/2 mi, the engine will accelerate (I went up to approx 4k rpm) but trans will not shift gears.
***I noticed the cursor that highlights what gear you're selecting is gone, and if I select R or D a big Thud of engagment.

Next Scan

Engine:
1405- No CAN message was received from control unit Transmission (U0101)
Antilock Brakes:
6106- No CAN message was received from control unit Engine control module or N15/3 (Electronic transmission control unit))
Electronic Ignition Switch:
B2254-64- The Electric Steering Lock Has A Malfunction. There is an implausible signal
OBDII :
U0101: Lost Communication with TCM

This all seems odd to me so I immediately thought it was the TCM, I dropped it, everything looks normal, tested all the solenoids etc. I was looking at board repair businesses and it appeared most just repair the speed sensors so I relayed my issues and codes, and they said they couldn't help.
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So i reinstalled the TCM and Valve body today, No pan or fluid yet, I wanted to check a few things before I rule out TCM for sure.

Fuse 27/ Good
Relay/ Good

The 4 prong round plug at the trans, I'm getting 12.3 volts, prongs look good. I also tested the board at the plug and was getting continuity from the prongs to the circuit board.

Im a novice when it comes to CAN systems:
I did test the CAN wires of the TCM and read 51ohms
I test the corresponding plug and read 2 ohms

I started trying to physically trace where the TCM plug comes from, however I'm going to hold off until Iget some educated advice

I did find this thread which seemed very similar to my issue, however the tread never was finished.
Similar issue?

You guys are awesome, I appreciate your time!
Thanks!
-Chris

GangStar

I wanted to follow through with the fix on this....

So the TCM processor went bad, which causes no communication.

I don't have the capabilities of programming a different TCM so I ended up taking this to the dealership.

They replaced the TCM with a Benz Refurbished unit, and the car had a hard shift into 2nd gear. The dealership suggested a new valve body, however the car shifted perfect before the TCM failure. I decided to take the car and see if it would self learn. I drove it for 2 weeks and it never got better.

Took it back to the dealership, and they replaced the valve body, and that didn't solve the problem either.

They then ordered a new valve body and TCM that are a matched pair. That cured the problem.

I feel like I was overcharged a bit for the dealership to learn how to solve this problem.

If you need this repair done I'd estimate around $2700.00

MBENZTECH

I'm surprised the dealer replaced just the TCM if there was no communication with the old one. Anyone that has been around Mercedes Benz 722.9 transmission knows that when replacing just the conductor plate, you have to transfer the data from the old one. If there is no communication with the old one, you have to install a COMPLETE valve body, which come with a new conductor plate/TCM. Now, a Mercedes Benz specialist like me, knows how to write custom flow data to the new TCM without the need to communicate to the old one. So, I hope you didn't have to pay for 3 different repairs.

That1person

did you have to take in your car to get these things fixed? Or were you able to just bring the valve body in and they do the programming there? My Mercedes dealer is 50 minutes away and I don’t really want to pay that towing fee.

Banzi

Hi Guys.

I Have a W204 C200 CDI. Drove the car most of the day running errands, the car was fine, no issues. Last stop before getting Home, the car would not start. At first I thought it was the starter, but when I scanned it, I got a U0101 code (Lost Communication with TCM) multiple resets, but the car still won't start. I've also checked all the fuses and all seems ok.
Is there any other way to reset the TCM and where is it located?

Please HELP?

JettaRed

iTrader: (1)

What scanner do you have?

Banzi

Its Konnwei 850 and I also used a Launch diagnostic. Most of the errors are cleared, just the the ones related to the TCM remain.

That1person

howdy! Your problem is as you stated the cars not communicating with your tcm module inside the transmission. This would put the car in a fail safe mode as it has no way to communicate to the transmission. On the passenger front side of the car, there should be a circular harness that connects to your transmission, go ahead and check that. (I think there’s a bracket covering it might need to remove it). If it’s properly connected, I would start looking in the direction of replacing your conductor plate in the valve body and or checking the harness for damage. The symptom sounds to fimiliar with what I had going on, where when I would disconnect the tcm connector (trying to diagnose something else) the car wouldn’t even attempt to start. But when I went down there and clicked it back in, boom cranked and turned over. The connector does have a locking mechanism, so I would bet either somewhere down the connector it got damaged and or as previously stated, the conductor plate took a dump on you. Hope this leads you in the right direction!

That1person

If you are referring to the ignition/petal sequence that supposedly “resets” the transmission module, that for resetting your driving profile adaptions not the physical tcm. The 722.9 builds a profile based off your driving profile and from there adapt to them. So if you have a lead foot, the car will recognize that and be a little more responsive rather than someone who’s a little more cautious and slow. Hope that clears that up!

Banzi

Hey.
Thanks a mil.I'll give it a go and pray it works.

Pierre Sutton

Same issue, Y3/8y4 fault then limp mode, so removed conductor plate but broke it upon removal flex ribbon and all. Bought a donor from junk yard had virginized and cloned, and it works except hard shift from 1st to 2nd and funny downshifts, looked at codes and says No communication error. U0100

So in this case, I have the old broken plate and i decided to do a little solder and uv mask repair on it, including plastic welding on the broken legs. I am going to remove the donor plug and plug this old one back in and see if it communicates. if so my donor has a bad tcm. I will post findings. Your the first post I've seen close the the issue i've been having






. and I will not to the route of Dealership.

JettaRed

iTrader: (1)

What car are you doing this for?