Why don’t you take it to a different shop and have it fixed properly

 

I've searched around for other shops but none of them had a clue what was going on despite me clearly telling them. So at this point I'd rather have no one work on the car other than myself.

Also, the car drove far better with the tc lockup function disabled than it ever did even before this whole issue started. It feels more responsive and alive without that torque converter locking up in every gear during acceleration, even if it's functioning properly. So at this point I'd rather disable it, at least temporarily until I decide to just get a brand new valve body.

 

I can not help with 'permanent' disable of the TCC, BUT--based on millions of transmissions for many years in all horsepower/torque ranges, WITHOUT any 'lockup' capability' and no problems---it is highly unlikely any part in your transmission will be negatively impacted. However, since your car was 'optimized' for a TTC, the efficiency loss without the TCC will be slightly greater than if it were 'optimized' for no TCC. BUT, without the TCC, torque applied to the drive train WILL be smoother and the gears, bearings, thrust washers,etc. should have significantly longer lives. Significant? not sure, but perceived 'smoothness' is worth a lot to me--and is difficult and costly to 'design in' the vehicle.

TCC feature is positive for fuel economy---nothing else. The incremental economy is tiny, and IMHO, if the additional weight and controls complexity are fully considered, there is very very little economy benefit in the real world. Any 'efficiency loss' in the TC has to appear as HEAT in the transmission oil, but is trivially tiny in 'real world' operation.

 

Why not just replace the TCC solenoid yourself? It's not that difficult or expensive, and it will probably fix the problem, it's just not guaranteed. That's not a bad proposition.

Nick

 

Any Chrysler shop should be capable, as they use millions of these transmissions.

 

I wouldn't want to risk replacing the valve or solenoid again, it might end up not fixing anything or even make something worse. The bore where the solenoid/valve sits probably is worn out too from all the locking/unlocking over the years. I'd rather just disable the function entirely.

My 2002 G500 never locks the torque converter while driving or cruising, and I've never noticed this for 6 years owning the car until now. The engine output on that car is incredibly smooth, and the transmission shifts like butter. I've always wondered why it shifted and revved so much smoother than my two s classes, and now I know why - It's because the torque converter never locks up! I would much rather take an extreme difference in drivetrain smoothness over a minuscule increase in fuel economy.

I wonder why the torque converter never locks up in my G500. Is this normal for g wagons? Or did the previous owner somehow disable the lockup function due to similar issues? If it was purposely disabled then I would like to do the same to my S600, and it relieves me to know its possible.

 

It's not just economy - it's heat. Locking the TC greatly reduces heat. When the fluid is churned up by the action of the TC, you get a lot of heat, and the more throttle (power) you use, the more heat you get.

 

I checked the cats using the old rubber mallet trick and reading the o2 sensors to determine if they were bad. According to these two tests, they checked out fine. Is it possible for there to be a very small blockage that isn't detectable unless looking into it directly? And would it be enough to cause my symptoms? There were no TWC damage cyl codes. - These will only show on DAS!
No, look inside them!

 

Never got any codes for TWC damage, even using DAS. In fact, there were no codes at all with DAS. No fuel injector codes, no o2 sensor codes, no tcc solenoid codes, nothing. Even if the cats were clogged, I believe performance will suffer consistently, but in my case the power comes on/off/on/off intermittently. In fact the issue doesn't exist at all in first gear, because I believe the tc never locks up in first gear. If it were a clogged cat I don't think first gear would be as violent as it is currently.

This is the one time I would pray for a CEL to come on, because it has been near impossible tracking down the problem. But I do really believe just disabling the tc lockup will fix my issue. My g wagon tc never locks up, whether by design or not, and that car has been performing flawlessly with no issues since the day I got it over 6 years ago. I don't think the additional heat will be a big issue, since I've never had problems with it in my g.

 

I believe you think the problem with a clogged cat is purely mechanical: the exhaust not having “room” to escape.

You have to take into account that cat clogging derives in an electrical problem when the ECU decides to cut ignition to protect te engine.

 

Guys I think he already narrowed it down to the TCC as that is what he had worked on when the problem developed, by turning it off the problem disappears , and the mechanic just doesn’t want to fix it again for free

 

Yes, thank you. I've already narrowed down the issue to the TCC. Since this issue began right after the TCC-related transmission service and ceased to exist once the lockup function was disabled, it would make the most sense to start with that.

I want to disable the lockup for good, then drive the car for a while and see how it performs this way. If the issue completely disappears, then I know I would have found what it was. At the very least, it would make diagnosing this issue much easier.

Since this issue ceases to exist once the TCC is disabled, I strongly believe there is nothing physically wrong with the torque converter, valve body, or solenoid. It is entirely a programming or software error. The computer sends incorrect signals to activate the TCC at inappropriate times. Since the TCU SCN coding didn't do anything to solve the problem, I would like to think the bad signal to activate the TCC comes from elsewhere, and I'm not willing to track that down right now. The car's computer looks at a wide variety of parameters to know when to lock or unlock the TCC, such as air/fuel ratio, coolant temperature, etc. so it will be devastating to track it down. It's much easier to just disable the TCC, at least temporarily until I find the real reason for the random locking/unlocking.

I've come across other forums where people disabled their TCC lockup function in other cars, and they say you either have to find and disconnect the wire that sends the signal to activate the TCC or do a physical modification to the valve body to prevent the TCC from engaging. I would much rather find the source that powers the TCC and disconnect it rather than doing any physical modifications, since it is easier to reverse a disconnected wire than a physically altered valve body. Does anyone have a clue where to start with this? Any wiring diagrams that show how the TCC is powered?

 

Ok I found the wiring diagram for the TCU and the wire that signals the TCC to activate.




If I disconnect wire #17 then my problem should theoretically be fixed. I just want to know before I do anything - will the transmission go into limp-home mode if I just simply disconnect it? Will the TCU freak out? What is the proper way to go about doing this?

 

Has there been any development? If not solved yet, I would recommend you change the solenoid and electrical plate.

 

To 'permanently disable the Trans convertor clutch, disconnecting terminal 17 should do that without any problems. It MAY throw an error code such as 'TCC solenoid failed open'
I would simply locate the wire at a convenient location and cut it. sealing each end to prevent any chance of moisture or a short.

 

I would cut the wire and insert a single-pole, single-throw toggle switch in the wire in an accessible location. This would allow you to have the circuit on or off with no problem.

 

Does anyone know which color the wire is? I cannot pinpoint which wire goes to the #17 terminal.

 

Hello Alex,
About 9 years ago the service manager in the Delray Beach dealership showed me a transmission with a damaged valve body. According to him it was caused by the wrong transmission fluid used by an other dealer. I could see that the plastic of the coil holders was damaged. They changed the whole transmission. These transmissions are sensitive to the type of transmission fluid used.
I remember one of your prior posts saying that the color of your transmission fluid was different from an other equivalent car. Maybe this could be part of your problem.

 

I found out the yellow/gold transmission fluid is normal, it's one of the MB approved fluids along with the red one.

On another note, I decided to remove the TCM and check for any abnormalities. I found that it was full of oil, so I proceeded to clean it extensively in hopes of solving the issue. Unfortunately I didn't notice any differences after the cleaning.






During the process, the small capacitor broke off and I decided to put the TCM back in the car without it.

What's the purpose of that small capacitor in the TCM? The car seems to run just fine without it - is it safe to keep it that way or should I solder on a new one?

 

You can rest assured the capacitor IS NEEDED for the TCM to 'live' and 'perform properly.' Hopefully someone of this forum can explain exactly what its function is. IMHO you need to either replace the TCM ASAP, like right away, or have it repaired , After all, the transmission failure will cost at least $4000 to fix.

 

The purpose of a capacitor is to smooth out voltage going into a circuit. I don't know its exact function in this specific application, but I bet its the same as in any other circuit.

It definitely isn't necessary in this application (hence why the car runs perfectly fine without it), but it is a good idea for safety reasons just in case there was any sudden voltage spikes going through the TCM circuit.

I definitely don't need to replace the TCM or transmission because this little thing broke off - It should be fine for the time being until I find the time to solder in a new capacitor in the near future.

 

I found the same capacitor loose in the case when I opened my TCM (2003 S430) for cleaning. It wasn't a big deal to reinstall it, after I found enough photos to give me the correct polarity.

My attitude was that Mercedes wouldn't have put it in there if the circuit didn't need it.

 

you mean you didn't do this first????
This is a classic discussed on these forums for ages!!!

 

I would strongly suggest that you replace this part with the same one. This is a 100uF 50V Electrolytic capacitor generally used in applications were current fluctuations will cause corresponding unwanted voltage changes. It will smoothen the voltage. They are easily available. Don't know where you are located, Digi-Key is a good source for these parts.

 

Have you ever thought of becoming an automotive tech? Don't!!

You have ignored / dismissed everyone who has posted and you also imagine that you're way ahead of the engineers who designed the car.

You are completely delusional and have no idea what you're doing!

I would not want to buy a car (half-assed and hacked) from someone like you.

You think you're the only one capable of fixing it? Laughable. Among other things (many), you can't even figure out which wire
to cut, going to the TCM. Despite posting the schematic! LOL.

It's a Mercedes, not a Ford Pinto!