Hi folks! I have about gone blind reading on this forum. Here is my story-

2001 ML320 bought used from a dealer with 96,500 miles on it. When test drove, car worked great. (I previously had a money pit 02 ML320, so I knew what to look for... I thought... but I digress...)

Had a problem with the battery dying. Never had to jump it, but I figured the car had sat for awhile on the lot. Dealer paid for us to get a new battery, we installed it, did all the steps. Problem fixed. I thought.

A few weeks later, when accelerating from a stoplight, car goes into limp home mode. I was right down the street from home, so I drove it home. Next day, started and drove just fine. It did this a few times, and restarting the car made it reset fine. Then, it would go into limp home mode and the CEL would come on... but again, restarting cured. It did this for about another week. Finally, the CEL light came on, it went into limp home mode, and restarting didn't fix. Damn.

I parked the car for about a month. During this time, I lost all the power steering fluid due to a leak in a hose, so it was no longer driveable to limp to my mechanic. So it sat for another month. I had it towed to my indy mechanics shop... where he fixed the power steering thing with a new hose and fluid, but the codes for the CEL were P0715 and some other code for an engine misfire. The car runs fine (with a slight engine skip, but I figured from past experience that it needs new plugs and wires... maybe coil packs.) but still in limp home mode and CEL on. My mechanic had a tranny shop look at it for a second opinion, and they agreed it needed a transmission replacement.
I refuse to believe that a luxury car with less than 100k needs a totally new tranny so I started my research. I found that we could replace the conductor plate for $250 plus labor and misc parts/supplies, so I asked my mechanic to do this. After I showed him all the research I had done, he agreed.

He replaced the plate, "cleared" the code. CEL still on, still in limp home mode.

He sent to his friends tranny shop. They took it all back apart to verify he did everything right (he did) and attempted to clear the codes with 2 super-wamperdine code readers. CEL still on, still in limp home mode. Still P0715 code.

Called the local dealer. They said to bring it in, and for $125 an hour, they will try to figure out what it wrong with it. They said that the P0715 code was useless to them, it is a generic code and there could be other things wrong to give that code other than the conductor plate. This is the same dealer who, by the way, insisted that I have my cylinders pulled for my last cars misfires... that only needed new plugs/wires/coil packs, so I don't have a lot of faith in them.

This is ridiculous... do I need to ask a shop if they have a specific code reader to clear the code? What else could it be that is giving the code? The tranny shop said everything inside looked fine... a little worn, but fine. I have read Gilly's posts extensively, and I am sure that some of you guys on here can help me.
Please help me! Broke at christmas and need my car!!! By the way, bought the car in June and have barely been able to put 1,000 miles on it!!
I love these ML's, but dang!!! Please advise, oh knowing ones... My mechanic is interested too!
Michelle Cordes in Washington

You sposed to do that on that other forum. Just kidding, welcome aboard.

You got to get someone with a Mercedes Benz SDS "super-wamperdine" code reader to tell exactly what is going on. May have to find another independent mechanic to get it.

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Jim

Ditto!

You need to have the code(s) read & cleared from the TRANSMISSION computer as well.
The code P0 715 is an engine code that points to a trans issue and means to read trans codes.

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A shop equipped with an SDS, and someone who actually knows how to use it to diagnose transmission issues is what you need. Also, I don't see any mention of checking the transmission ECU for fluid contamination. This is one of the first/simplest things that should have been done.

Find a competent, properly equipped shop and stop wasting time and money on expensive guesses.

It was checked for contamination before we swapped out the conductor plate and it was fine... And as far as the fluid....dark fluid, little bits of metal. Nothing big. And I just held the old plate in my hands yesterday... it was pretty worn compared to the new one...

I have found a local shop that specializes in Mercedes and BMW, and prides themselves on being the less expensive dealer alternative... and is close enough to drive to in limp home I'm calling later today... any other advice on what I should ask them?

Thanks for the input already guys, I appreciate it....

Let us know what kind of codes they get out of the transmission.

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Jim

Yes! Assuming they have an SDS, they should check the transmission adaptation data. This is the best way to determine the condition of the shift members without tearing the transmission down. Let us know what happens.

Hi, I just read through this, haven't been watching the ML forum like I used to. All makes sense to me, if it wasn't the conductor plate or connector not sure where to go now except what has been recommended. Could possibly be the fluid-in-the-ETC problem as noted, or maybe the shifter, you haven't dribbled into the shift gate have ya?
Shouldn't take SDS to get the ETC code, but probably going to take more than what autozone uses.

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Thanks for replying, Gilly!

Ok, I have found a reputable, independent European import repair shop, and I spoke with the owner at length today. My car is going in on Thursday... he is going to hook it up to the SDS (yay!) reader and see what he may see. His estimate is one hour, and he will call me if it needs more.

I am optimistic that it will be only an hour. Wagers? LOL

So, I'll post results Thursday...

The first thing to do is perform a short-test. This will tell you if the transmission ECU and shifter ECU are able to communicate with each other, among other things.

Reading the adaptation data should only take fifteen minutes. If he finds any readings at +/- 180 it's time for a new transmission. If the adaptation data checks out OK, take a look at the RPM sensor values.

It's entirely possible it will take less than five minutes.

Assuming the issue was related to the conductor plate, once it was replaced the codes had to be cleared properly. Typical OBD-II scanners will NOT clear the code from the TCU/TCM, so your vehicle is still "broken." This would be the case even if you installed a brand-new transmission.

The first thing I'd have the shop do is to read and then clear the codes with the SDS. Then test drive it. Likely it is fine...assuming the conductor plate was the issue to begin with.

Good luck.

I respectfully disagree. The presence of stored fault codes will not affect transmission function. A current fault might cause the transmission to go into "limp" mode (depending on the code).

For example, most conductor plate failures are due to implausible readings from one of the RPM sensors. Typically, the failed sensor will send a signal to the ECU indicating 8,000 RPM (it will read 8,000 RPM even with the key ON, engine OFF). This is the default value. The ECU knows that 8,000 RPM is implausible and goes into "limp" mode to protect the transmission from damage. Cycling the key will restore normal operation as long as the RPM sensor starts working correctly again, but a fault code will be stored in the transmission ECU. If the sensor continues to misbehave, the transmission will remain in limp mode.

It's very important to understand the difference between "stored" codes and "current'' codes. As I posted previously, "a shop equipped with an SDS, and someone who actually knows how to use it to diagnose transmission issues" is what Nailgirl needs.

Sounds crazy but it might just work...........

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Assuming arguendo that is an accurate description of how the system is designed to function, I've seen just what I described.

That said, I agree that while anyone can be handed a tool -- and even trained how to use it -- only some can actually use it properly; moreover, as I noted, my comments are premised on the conductor plate being replaced as a result of a *proper* diagnosis. If it was guesswork, there is still work to be done...which starts with a correct diagnosis. And hence my use of the conditional "might."

Ultimately our goal is the same, helping the OP get down the road with a working vehicle.

Just to step back and see what you both are saying:

All we can do here is look at what is being said and accept it at face value.

If the conductor plate was the problem, it should now be a stored code, not a current code, and as such we can assume that it is out of limp home mode. But again we are assuming. Makes sense to me but sometimes the transmission has other ideas. That's the way it should be.
If you read the OP, either the indy shop did ththe conductor plate w/o success, although the work was based on a PO715 code and no codes from ETC, evidently, so kind of jumped the gun on even DOING the conductor plate, so IMHO the diagnosis was bunk.

So, to me, the Y in the road isn't so much reading/erasing codes and assuming everything will be fine and dandy (nice thought) but to read the ETC codes, then decide what to do from there.

Hard to swallow that the most favorable outcome is that the indy either sold a bad part or botched the instalation somehow.

We're all trying to help, sometimes you need to take a second look at what the problem is.

Gilly

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