Been lurking this site for a while now, figured I would sign up and start my own thread.

First off, I am aware there are a bunch of threads on similar issues, I have been reading through ALL of them. I am only posting my own because a LOT of those threads the OP never comes back after the trip to the dealer/shop to say what the actual repair that resolved the issue. And none of what I read resulted in the end result of what the Indy told me today. Just need a fresh set of eyes before I throw my hands up! Thanks

2002 C240 Automatic 66700 Miles

Symptom:

Car gets stuck in gears 2-5, Sometimes CEL sometimes no. CEL always clears itself after 3 restarts. Usually a off and on clears the stuck gear issue.
No noises, No chatters, No vibrations, no grinding, no slipping, Period!

Take the car in (Indy Foreign car shop), changes the pilot bushing, cleans the harness off, doesnt check TCU for contamination. Still has issue.

I, remove TCU, clean harness in the engine compartment side, no oil on TCU plugs. Did not open it and inspect.

Shop says, Its now the Conductor plate.

Take to a 2nd shop (Indy Mercedes only shop).

Shop says, its your conductor plate and valve body.

Changes conductor plate, Cleans, inspects valve body, another new pilot bushing. New fluid, new filter. Same issue. Drives fine for 1 day, 2 days, sometimes 10 minutes but still gets stuck in gears 2- 5.

2 days later shop is still stumped. I stand there and watch him running the Star Diagnoses. Comes back to check the TCU, Star Checks TCU no faults found. Owner of shop says hes taking to MB dealer for inspection.

This is my diagnoses today:

Clutch pack 4 is bad. Wants to rebuild the whole tranny. Says that why its getting stuck in forth. I say the day it came here it was stuck in 2nd and also gets stuck in 2-5. He says its slipping in 4th, I call BS! He trys to defend it.

Again, I call BS, and start asking questions for him to explain. Cant back up the Diagnoses he says came from MB Dealer.

When this whole thing started, called a friend who is a Parts Manager at a MB Dealer out of state from me. He explains the symptoms with some tech, Diagnoses (over the phone) is Conductor plate.

So what gives?

 

The car is going into limp mode. Please get hold of the entire Star diagnostic print out & post it - you have paid for it. Otherwise we are just guessing.

Have they tried reflashing the transmission software?

 

I was asking for the print out, nothing got produced! That's why I called BS.

After reading through all the post, I went into the whole thing wanting the TCU reflashed. It was the reason it was being taken to the MB Dealer. But comes back with the "Need the Tranny Rebuilt" crap.

I have been working and modifying cars and boats for many years, more then I care to admit. The w203 is a whole new beast to me. With that said I have NEVER seen a tranny need a rebuilt that doesnt display the normal slipping, grinding, vibration or chattering. Which is why the idea of spending that kind of money on it doesnt make sense to me.

New Question: Is it possible to purchase a used TCU and just plug and play or does it need to be flashed for the specific car(TCU VIN Coded)?

 

A new TCU has to be adapted with Star - easy process.

Tell these guys that you want the Star printout. The only way to measure slippage is input shaft data vs output shaft data & Star & the car will read that. If it's out of whack a code will be stored & it can generate limp mode. That does not mean the gearbox needs a rebuild. It could mean the gearbox needs to be set up properly with Star.

4th gear clutch pack is not a likely failure point. The first to second one way clutch is usually the first to go at extreme mileage & in taxi service on the 722.6 box. Just too many high torque changes in the end.

 

Can a Used one also be adapted for a different car? If so, whats the range of TCU's that can be used? For example, I have a '02 C240. Can I use a '05 C240 TCU? or a '04 C230 Coupes?

 

You can use any W203 722.6 TCU from about mid 2002 to end 2005. I'm sorry I can't give you VIN references. Earlier TCU's could not be reflashed. Probably safe to get one from 2003 onward. Then it requires to be flashed with the C240 software map as a 240 developes it's power & torque higher in the rev range than a Kompressor & the TCU must be profiled to take this into account.

Then one requires to adapt it with a Star so that it recognises the transmission it's being mated with. There is a setup procedure in Star.

 

If I got a 722.6 TCU from a 2004 C240 would it even need to be reflashed?

 

What's weird is if you got a CEL it should be stored even if it goes away so they should have seen a code.

I wouldn't say reflashed but maybe readapted with STAR

 

Can you elaborate?

The fault that I specifically saw star pull was to test the TCU. When star tested the TCU it came back saying no faults.

I was told that it came back with the TCU communication error, Valve Body fault, RPM Sensor fault and the best one a Slippage fault. Yet to see a print out of any of them.

 

What I mean is you can't just slap on a used TCU and have it work. It wont work you will need SCN coding so you'll have to make a trip to the dealer. You can't reflash the used TCU because the VIN of the other car is already on there. You will need SCN coding and the dealer to do this. The independant shops don't have account for SCN coding so they can't do it unless they get an offline hex code from the dealer (but most of the time they don't do that).

So my advice to you is contact the dealer and ask them will they be able to "SCN code a used TCU".

 

Here is a good example. This guy needed to change his TCU and he did but then had to take his car to get the SCN coding done.

http://www.youtube.com/watch?v=gzuXLRXXcew

Good Luck, but make sure it is the TCU because you spent soo much money already and I don't want to see you spend more money and not fix your issue.

 

I wouldn't say reflashed but maybe readapted with STAR

By this I meant maybe if they clear the adaptations and try to readapt it, it might come back to life because you can't reflash it.

 

No reflash required then. Just adaption. Same applies if you pop in a new gearbox with your old TCU. We helped someone with exactly this problem about a year back but I can't find the thread.

 

I will see if I can get it to the Benz Dealer on Monday when they open.

18 years of working on cars tells me its not the Clutch Packs! All this just seems very computer related.

 

Please demand a Star printout this time.

 

At the current rate of $149/hour to diagnose at the Benz Dealer, you can bet that I will get one!

 

Thanks for the help so far guys/girls!

Update:
My wife picked the car up the other day from the Indy MB shop. Guy said it would be ready Monday @ 11am. She called and asked if it was ready to be picked up and he told her he needed another day. She said no, it needs to be ready now (She doesnt put up with peoples crap). He said give me a couple of hours and it will be done. She gets there a few hours later and its still not finished and they havent even started to work on it yet. She asked what they still have to do to it and no one will give her a straight answer. She asked if it was drivable, they said yes. She took it as is.

She pushed and pushed for the Star print outs and no one would produce them. He tried to give her a bill and she laughed at him. Told him she would pay it when he produced what we were being billed for. Not a hand written diagnoses. He told her to have a nice day then.

But, He cleaned the valve body, replaced the Conductor plate, new pilot bushing, new fluid, filter and gasket. With no charge!

So on Monday it goes in to the MB Dealer.

On a side note, when I got home I pulled the TCU back out and opened it up. Not one drop of oil on the pins or in it all! The harness does have oil on it, but I dont see Tranny fluid eating through the wire jacket and corroding the wire itself. Unless someone tells me that the Synthetic fluid is also a mild acid that is eating plastic!

I will keep you guys posted!

 

As long as oil is not on the pins at either end of the TCU harness you are OK. Oil between the pins changes the values the TCU sees as oil is slightly conductive.

 

Hey Guys,

Just an FYI the video you posted is a car with a 722.9 transmission.

The op's car has a .6 transmission. The .9's need to be SCN coded.

 

So this is what star came back with:

Code: P207B - Read fault memory from control unit Transmission and rectify faults.
Code: P2069 - Fault is stored in component N15/3 (ETC [EGS] control unit). (P0730)
Code: P2502 - The gear is implausible or the transmission is slipping.

BTW, I have the STAR Printout in my hand!

 

Anyone want to take a stab at my issue?

 

P2069/P0730 = Incorrect Gear Ratio
P2502 = The gear is implausible or the transmission is slipping.

You either have a wonky speed sensor or the transmission is slipping. Input speed is taken from the engine/TC out. Output speed is measured by a sensor in the transmission on the output shaft. Any implausible speed registered for the gear you are in would tend to place the car in limp mode to prevent further damage.

Did the transmission filter show a lot of wear debris/clutch material?

 

Conductor plate is new.

No wear at all! No debris, no sludge! Tranny is clean. and only 66000 miles!

Could these issues be caused by a bad TCU? TCU was not able to be re-adapted. Communication fails.

 

Early TCU's could not be reflashed - you might have one of those.

Corrupted TCU or damaged TCU could cause this problem. Oil in harness to TCU could also cause incorrect sensor values.

Unplug the harness from the transmission & check that there is no oil leak from the bush.
Can you borrow a TCU to see if that is the issue?

Good luck!

 

There is oil on the harness non on the pins, or plugs. Have opened the TCU and confirmed no oil inside.

Can one from another c240 be used? Plug and play?

Anyone near Irvine, ca wan't to loan me theirs for 20 minutes?