Anybody knows their Mercedes Benz transmissions? Limp mode question

Joined
Mar 8, 2014
Messages
9
Location
NJ
Car in question is a 1999 Mercedes Benz CLK320 which I believe has the 722.6 automatic transmission. 75k miles on car.

Previous to this incident car ran flawlessly.

While driving, the check engine light came on, two miles later I see smoke pull over, look underneath the car and the transmission was covered in fluid. Drive another 2 miles to pull off the highway and notice the car does not shift out of 1st gear. Call tow truck and have car sent to a local transmission shop.

They look at the car, replace a few o-rings and "service" the transmission to the tune of $450. They tell me they did not experience the limp mode stuck in first gear issue on their test drive.

I get the car back and after driving 10 miles again the transmission is in limp mode and stuck in 1st gear. Bring it back to the shop. Check engine light came on P0715.

After two days they say they have replaced the 13 pin connector which is known to cause issues. They argue while on their test drives the transmission operates correctly. They want to charge me another $450 for the service and I say you already serviced it last week so they bump it down to $200. 3 miles after picking up the car it is in limp mode and stuck in 1st gear again.

At this point I do not want to take it to them again. Clearly they dont know what they are doing.

Any pointers here? I have read about the conductor plate being a possible culprit. Also about the TCM being flooded with oil although I would have expected them to check that when replacing the 13 pin connector.

Important to note that when the car is shut off and restarted the transmission is back to normal and shifting correctly.

Any help is appreciated.
 
Next time the limp mode happens, dont switch off if you can - get somebody with a STAR or any MB speaking scanner to look at the current codes before the restart clears them ............... they normally will tell you immediately whats gone wrong.
 
We had a similar problem on an 01 e320, dealer may be the only way to properly service without the special software. $3000 later, oil in trans computer problem etc, we still had CEL lights coming on and problems. I had a hunch and replaced the voltage regulator inside the Bosch alternator, about $100 at the dealer. No problems after, if the voltage spikes or fluctuates it sends the computers into a tizzy. I have a feeling this was the whole problem. Yours may be different of course.
 
civhatch90-I have that transmission and my 2005 cdi has 312,000 mi. Typically, MB forums say that the pin connector was a weak link and they changed the O-rings. What would happen is that fluid would wick up the wires to the computer causing problems and this fluid would have to be cleaned out. I have changed my connector 2-3 times. The plastic connector costs about $20 at mercedes and is held on with one 7mm screw/bolt. Go to Mercedes-benz forum and search or google.. Once the bottom cladding is removed, this is a 10-15 min job but the fluid that seeped past the O-rings (2 I think), that must be cleaned out. I have not done that. I changed the original connector (with the ill fitting O-rings) and now change it out every 4 years or so just as a $20 precaution. steve
 
Agree with Steve. Fluid has likely wicked up the wiring and contaminated the TCU...flush out the TCU and wiring harness with contact/electronic cleaner and see if that helps.
 
Originally Posted by steve2016
civhatch90-I have that transmission and my 2005 cdi has 312,000 mi. Typically, MB forums say that the pin connector was a weak link and they changed the O-rings. What would happen is that fluid would wick up the wires to the computer causing problems and this fluid would have to be cleaned out. I have changed my connector 2-3 times. The plastic connector costs about $20 at mercedes and is held on with one 7mm screw/bolt. Go to Mercedes-benz forum and search or google.. Once the bottom cladding is removed, this is a 10-15 min job but the fluid that seeped past the O-rings (2 I think), that must be cleaned out. I have not done that. I changed the original connector (with the ill fitting O-rings) and now change it out every 4 years or so just as a $20 precaution. steve


Thanks for the feedback. I will check. The second service performed by the shop was to replace the 13 pin connector which is what you are suggesting. I am not sure if they looked at the TCM to see if it was dry or not. I will take a look.
 
Originally Posted by edwardh1
sounds like a tsb is needed, but not likely on a 99


He could look it up in the WIS. Not sure about that year, but yeah, the pilot bushing/connector typically goes. Also conductor plate can go too, but worse case is replacing the entire transmission. When it happens, you should have a scan tool that can read MB specific codes including transmission. The Autel Diaglink can do it and is about $85 on Amazon although it's been as low as $79.

https://www.amazon.com/Autel-Diaglink-Version-Diagnostic-Transmission/dp/B01N0QQZY7

The WIS is about $6.60 on eBay and it's basically the full MB shop manuals that the dealers use. One of the few cheap things about Mercedes...

https://www.ebay.com/itm/Latest-201...orkshop-Manual-Full-version/123679649919
 
Like others have said the electrical connector at the trans was leaking, we did about a million of these under warranty when I was at the dealers in 02-03. What they should do is remove the electrical plug at the trans again, you can do this if youre handy, and see if theres oil in the male side. If so clean it out with brake cleaner, and find where the TCU is, it may be up under the floor on the passenger side, remove the mat and the carpet and theres a stronger foam insert with the TCU on back, IIRC. Unplug the computer and clean all of that out with plastic safe cleaner, same for the plug. We used to wrap them in towels overnight to try and wick the rest out. The oil creates a short and freaks everyhting out, so you may need to go back in a few times and get the rest out.

https://www.youtube.com/watch?v=QvwxeCy8xRQ
 
Originally Posted by Audios
Like others have said the electrical connector at the trans was leaking, we did about a million of these under warranty when I was at the dealers in 02-03. What they should do is remove the electrical plug at the trans again, you can do this if youre handy, and see if theres oil in the male side. If so clean it out with brake cleaner, and find where the TCU is, it may be up under the floor on the passenger side, remove the mat and the carpet and theres a stronger foam insert with the TCU on back, IIRC. Unplug the computer and clean all of that out with plastic safe cleaner, same for the plug. We used to wrap them in towels overnight to try and wick the rest out. The oil creates a short and freaks everyhting out, so you may need to go back in a few times and get the rest out.

https://www.youtube.com/watch?v=QvwxeCy8xRQ


Well I am assuming the actual connector was replaced since that is what the mechanic said he did. I highly doubt he checked the TCU so that is what I will do next before anything else. Thanks so much for the input.
 
We had a similar problem on an 01 e320, dealer may be the only way to properly service without the special software. $3000 later, oil in trans computer problem etc, we still had CEL lights coming on and problems. I had a hunch and replaced the voltage regulator inside the Bosch alternator, about $100 at the dealer. No problems after, if the voltage spikes or fluctuates it sends the computers into a tizzy. I have a feeling this was the whole problem. Yours may be different of course.
Even a battery fart will do that.
 
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