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722.9 transmission fault, second time: valve body/conductor plate (control unit)?
I have a 2007 E320 Blutec. (It is branded Bluetec, but I believe it is the last of the CDIs). Regardless, it has the 722.9 transmission.
About 80,000 miles ago I had the conductor plate rebuilt. What I am calling the conductor plate is the black piece of plastic (attached to the valve body) that has eight solenoids on it. I have also heard it called the Electronic Control Unit.
I had it rebuilt (Y3/8n1) from an outfit in Van Nuys, California. It worked great for about 80,000 miles--which was certainly the neighborhood of the miles I got out of the original unit/fluid.
During the pandemic, we have been driving the car only rarely. During the last ~four months, my wife noted that the transmission "shuddered like mad" on two separate occasions. The first time was when she was approaching a red light on a freeway offramp. The car shuttered, then died. When she started it up again, it was just fine. The second time it was as she was getting up speed first thing in the morning. She pulled over and (remembering how restarting the car the previous time "fixed it") turned the car off, then restarted it--and again the problem went away.
(I thought perhaps the transmission fluid was low, or in need of a service. I even bought some fluid before I found out that topping up the transmission fluid is no easy task. I researched on the boards here a little bit to read that on occasion the dealership will have transmission flush specials, so I made a point to keep my eye out. I remain confused that in 2007 the car was sold with "lifetime transmission fluid," and now the exchange interval is as few as 40,000 miles.)
I decided to drive the car recently--since one of my theories is that it is suffering from not being driven enough. It wouldn't shift out of second gear (since we typically run it in Comfort (not Sport) mode). It was running at 4000 RPM at 25 or 30 mph. I turned around and drove it straight home.
I put it on my Harbor Freight Scanner and it said P2767: Input / Turbine Speed Sensor B Circuit No Signal.
I can see from the website of the company in Van Nuys that P2767 is another of the six codes they will fix. (Originally my conductor plate threw code P0717.)
I called around a couple of independent shops and a couple of dealerships hoping to figure out how much the repair would cost this time.
Two dealerships quoted me roughly $2600 for a Mercedes-rebuilt valve body, which will come with a conductor plate. (That $2600 includes a core charge for my valve body.) The independent shop will rebuild my conductor plate and valve body for $1500. If I wanted the dealership only to replace the conductor plate, that would be about $1000. The dealerships were all emphatic that the electronic control body and conductor plates are both Theft Relevant Parts--available only at authorized dealerships, and must be installed at the dealership.
If I only had to question whether the 14-year old car with 200,000 miles is worth $1500 or $2600 to repair, I wouldn't have started this thread. But here's where it gets interesting:
Remembering my wife's story that restarting the car eked out better performance, I took the car for another spin. In Sport mode, I could now appreciate that the car would shift into second, but not into third or above. Leaving the car to coast down a gentle incline, I dropped it into neutral, turned the car off (coasting at maybe 5 mph), then started it back up. Sure enough, it would now shift into higher gears. I didn't drive above 50 mph, because I am sure something is wrong with my transmission; I'm just not sure what. UPDATE: With the P2767 (Internal Turbine Speed) malfunction, starting the car from Park will give 1st gear and reverse. Starting the car in Neutral will give 6th gear (but no reverse).
So, I have at least the following questions:
Is the conductor plate and the control unit the same thing? (Update: Answered, yes they are the same.)
If it's really a faulty turbine speed sensor, is there any point in replacing the valve body? (Remember that the car has 200,000 miles on it.)
What does it mean that sometimes I can restart the car and it will escape limp mode? (Update: starting the car in Park will give 1st/Reverse. Starting the car in neutral will give 6th gear.)
If I invest in a better OBD scanner, will I be given any more specific information about the fault in the conductor plate? Is it possible this is just dirty fluid? (In other words, might a proper valve body flush be in order, not a conductor plate replacement/rebuild?)
If I stay with the independent shop, will they be able to reprogram a new/rebuilt valve body? What about a new/rebuilt conductor plate? Is that something I can do myself (with the right scanner)?
I see that one outfit in Florida will sell me a refurbished valve body/conductor plate and a 3-year, unlimited mileage warranty. I would have to arrange to have my new parts scanned in order to get out of limp mode. What is the best scanner I should buy if I want to do that myself?
If I drop my pan, soak/clean my valve body, then take my conductor plate to Van Nuys for another rebuild/diagnosis, will today's code P2767 be enough for them to fix it again? I would really, really hate to go through the bother of dropping the pan, sending the part off, and reinstalling it only to find that my Harbor Freight scanner gave an inaccurate diagnosis. (Update: P2767 is enough for them to diagnose the failing component in the conductor plate.)
What does "on-line SCN coding" mean? Does that mean that I can get a bluetooth OBD dongle and they can recode the new parts to my car from their shop via the Internet? If that's the case, can I buy the same bluetooth OBD dongle and ask them first to do a better diagnosis?
Those are my questions right now, but I am sure I will have others. I thank you in advance.
Last edited by wukinpanub; 05-02-2021 at 04:22 PM.
Reason: Clarity, accuracy
You're about to waste a whole lot of time and money. The real, and only problem you face here is that @ 200k miles there should be no repair attempts made on your transmission. Only a full replacement with new torque converter. At a dealer that would cost around $9,000 which is more than your car is worth. A transmission shop may "rebuild" for half that, but successful results are not guaranteed. Unless the rest of the car is in excelllent condition, then it's time for the scrap yard. A properly maintained (meaning fluid and filter changes every 40k miles) 722.9 transmission can last about 250k miles.
Last edited by E55Greasemonkey; 05-01-2021 at 10:40 AM.
If the car is a goner, then I have nothing to lose by dropping the transmission pan, cleaning the valve body as best I can, +/- wasting no more than $200 on another conductor plate rebuild.
If I drop the pan and screw something up or become convinced the valve body has had it, I'm no more than $600 away from a rebuilt valve body/conductor plate with a 3-year warranty. No, the car is not worth an investment of $9000, but, yes, investing ~$1500 in a car we could let the kids use (knowing it might be wrecked inside of 50,000 miles) seems reasonable.
Does it mean anything that I can manipulate the car out of limp mode? In my mind, that makes me think a fluid flush might help. On the other hand, it could hint--as others are suggesting--that the problem with the conductor plate is only the beginning.
Thanks for the input!!
Last edited by wukinpanub; 05-01-2021 at 12:45 PM.
This vehicle is on the steep side of the downward slope in terms of utility. Cost+aggravation to keep it going is accelerating. It's your car and your choice.
For anybody following the topic in the future, here's a little something I've learned:
--I want an OBD scanner that will communicate with the TCU (Transmission Control Unit). (Cheap ones only communicate with the ECU (Engine Control Unit).)
--The module rebuilding pro assures me that Y3/8n2 is now a goner. It is not intermittently functioning, as much as I'd like to believe that from being able to escape limp mode. Exactly whether that means Y3/8n2 was in the process of failing over these last four months...I cannot say.
I believe that I have TCU version 2. I say this primarily because if I had version 1, a repair of the conductor plate independent of the valve body would not have been possible. I can't seem to find any information as to when the different versions of the TCU were rolled out.
I'm about 75% convinced that I'm going to drop the transmission pan for a look-see, with plans to invest ~$250 in a conductor plate rebuild and $150 in a fluid/filter. If I screw it up, I probably will have learned at least $400 worth of wisdom--which at this point is: stay away from Mercedes Benzes. (This is my fifth Mercedes diesel, and it is going to be my last; the lowest odometer reading I had on my first four inline fives was 177,000, and that odometer hadn't worked for at least three years. And not a single one of those vehicles had transmission problems into 400,000+ miles. Within 30,000 miles of owning this Bluetec (purchased "barely broken in" at 50,000 miles), I was handed a repair bill that was by itself more than I had previously ever spent on a Mercedes.)
For anybody following the topic in the future, here's a little something I've learned:
--I want an OBD scanner that will communicate with the TCU (Transmission Control Unit). (Cheap ones only communicate with the ECU (Engine Control Unit).)
--The module rebuilding pro assures me that Y3/8n2 is now a goner. It is not intermittently functioning, as much as I'd like to believe that from being able to escape limp mode. Exactly whether that means Y3/8n2 was in the process of failing over these last four months...I cannot say.
I believe that I have TCU version 2. I say this primarily because if I had version 1, a repair of the conductor plate independent of the valve body would not have been possible. I can't seem to find any information as to when the different versions of the TCU were rolled out.
I'm about 75% convinced that I'm going to drop the transmission pan for a look-see, with plans to invest ~$250 in a conductor plate rebuild and $150 in a fluid/filter. If I screw it up, I probably will have learned at least $400 worth of wisdom--which at this point is: stay away from Mercedes Benzes. (This is my fifth Mercedes diesel, and it is going to be my last; the lowest odometer reading I had on my first four inline fives was 177,000, and that odometer hadn't worked for at least three years. And not a single one of those vehicles had transmission problems into 400,000+ miles. Within 30,000 miles of owning this Bluetec (purchased "barely broken in" at 50,000 miles), I was handed a repair bill that was by itself more than I had previously ever spent on a Mercedes.)
The fluid is about $60 for a case of 12 quarts of Shell ATF 134 at a Shell distributor. Some distributors have multiple locations so you can check to see if there is one closer to you. Otherwise yeah at about $20 a quart I can see you spending $150+ on fluid and filters. It's an MB approved fluid.
For anybody following the topic in the future, here's a little something I've learned:
--I want an OBD scanner that will communicate with the TCU (Transmission Control Unit). (Cheap ones only communicate with the ECU (Engine Control Unit).)
--The module rebuilding pro assures me that Y3/8n2 is now a goner. It is not intermittently functioning, as much as I'd like to believe that from being able to escape limp mode. Exactly whether that means Y3/8n2 was in the process of failing over these last four months...I cannot say.
I believe that I have TCU version 2. I say this primarily because if I had version 1, a repair of the conductor plate independent of the valve body would not have been possible. I can't seem to find any information as to when the different versions of the TCU were rolled out.
I'm about 75% convinced that I'm going to drop the transmission pan for a look-see, with plans to invest ~$250 in a conductor plate rebuild and $150 in a fluid/filter. If I screw it up, I probably will have learned at least $400 worth of wisdom--which at this point is: stay away from Mercedes Benzes. (This is my fifth Mercedes diesel, and it is going to be my last; the lowest odometer reading I had on my first four inline fives was 177,000, and that odometer hadn't worked for at least three years. And not a single one of those vehicles had transmission problems into 400,000+ miles. Within 30,000 miles of owning this Bluetec (purchased "barely broken in" at 50,000 miles), I was handed a repair bill that was by itself more than I had previously ever spent on a Mercedes.)
Great comments. Welcome to the new Mercedes-Benz. Expensive short lived junk.
It sounds like you're willing to spend a little time, so here's what I'd do. It won't cost much to take a look. Remove the valve body, save the fluid in case the repair ends up being cost prohibitive. Check the pan for metal fragments, the overall fluid condition, and the pan magnets for a porcupine metal appearance. Look at the 2 black sensors on the top of the electric plate, towards the center, one of which you have the code for. If it's cracked or looks like something hit it, that means the transmission is worn internally and the tolerance of the rotating parts is far off enough to make contact at those sensors. At that point, a new electric plate (with control unit) can be fitted to (maybe) buy some more time. However, that is a theft related part and must be purchased from AND programmed by a dealership after it's installed. That's assuming they will sell it to you.
It would be beneficial before any of this to read out the clutch fill times with Star diagnosis (which you don't have) to see if you have excess clutch slippage, indicating the valve body/plate is the least of your worries. Typically though, you'd have some codes for slippage or implausible speeds.
Last edited by E55Greasemonkey; 05-01-2021 at 10:35 PM.
At that point, a new electric plate (with control unit) can be fitted to (maybe) buy some more time. However, that is a theft related part and must be purchased from AND programmed by a dealership after it's installed. That's assuming they will sell it to you.
I thought he was just planning on sending out the plate and getting it rebuilt? I think when they rebuild it, it's the same plate so it doesn't need to be programmed by the dealership after installation. Just have to wait for them to rebuild it and send it back to you.
I thought he was just planning on sending out the plate and getting it rebuilt? I think when they rebuild it, it's the same plate so it doesn't need to be programmed by the dealership after installation. Just have to wait for them to rebuild it and send it back to you.
Yes, correct, but if that sensor is cracked I don't know if they can fix it. I also wanted to bring attention to look at the sensor to determine a cause if possible. If cracked, a new/rebuilt plate may not last long until the sensor gets hit again.
Last edited by E55Greasemonkey; 05-01-2021 at 11:16 PM.
Check the pan for metal fragments, the overall fluid condition, and the pan magnets for a porcupine metal appearance. Look at the 2 black sensors on the top of the electric plate, towards the center, one of which you have the code for. If it's cracked or looks like something hit it, that means the transmission is worn internally and the tolerance of the rotating parts is far off enough to make contact at those sensors. At that point, a new electric plate (with control unit) can be fitted to (maybe) buy some more time.
It would be beneficial before any of this to read out the clutch fill times with Star diagnosis (which you don't have) to see if you have excess clutch slippage, indicating the valve body/plate is the least of your worries. Typically though, you'd have some codes for slippage or implausible speeds.
Thanks. That's the specific sort of advice I was seeking!!
After a couple of hours under the car I succeed in dropping the pan and removing the valve body and conductor plate. It was an easier job than I expected. Youtube has a helpful video. The most difficulty I had was in getting the car up on four ramps. I had to buy an E-torx-10 ("reverse torx"); I should have done that long ago. Also, make sure you have at least one T-30 bit. The only time I was forced to cuss was when I was removing the electrical connector. It took more massaging than it should have, and it is in such a position that manipulation is difficult. I made less of a mess than I feared. I had laid down a tarp underneath my drainage containers, and that proved a worthwhile investment.
In general, I was very pleased with what I found, and the ease of the removal. I would encourage others to do the job themselves if they are even considering it. I reserve the right to change my mind if somehow reassembly or refilling the fluid is more difficult than disassembly/drainage.
There was only a light dusting of a very fine, graphite-like metallic material on the magnet.
The fluid was dark, but certainly no darker than I was expecting after 80,000 miles. I have no prior experience, it should be noted.
I took a picture of the conductor plate, not that it will show anything. The two "towers" that Greasmonkey pointed me towards were free of trauma. I can see that the shorter of the two (closer to the large yellow circle) was where it was previously repaired. The electronics under the taller one is the one I presumed to need repair this time.
I cleaned the solenoids. I had read that a magnet will be useful for pulling the metallic dust from the screens. My screens didn't have any metallic dust, which I took to be a good sign. (I did manage to crack--then break--one of the pieces of plastic that surrounds the electrical connectors. I'm better than 98% that it can't possibly matter (the whole assembly will be bathed in transmission fluid, so it's not like the pieces of metal that lost a cosmetic cover will make and functional difference), but I suppose I will replace it out of an abundance of caution.
Last edited by wukinpanub; 05-03-2021 at 12:39 AM.
Reason: formatting
Thanks for sharing all of this. I am experiencing a flare sometimes 4-5 gear upshift, always 1-2 and harsh torque converter clutch engagement. I am following to see what solves your issues to begin going after mine.
I've included a picture of the solenoid with the broken plastic cover. As I mentioned, the cover seems primarily cosmetic. Transmission fluid is allowed to flow inside of the cavity even with the cover in place. I suppose the electric connectors will now see more fluid over their life than before...but I gather that doesn't matter. I would be happy to be informed that I am incorrect, however.
Great photos @wukinpanub please continue to document your journey.
Are you 100% sure that fluid enters the device with the broken cap? With a broken piece of plastic, both of the electric contacts are now exposed, and it's potentially possible that metal shavings/dust could intermittently bridge the two contacts. Probably unlikely. Not impossible in my view. The cover isn't cosmetic, there is no reason for cosmetics in this application.
Great photos @wukinpanub please continue to document your journey.
Are you 100% sure that fluid enters the device with the broken cap? With a broken piece of plastic, both of the electric contacts are now exposed, and it's potentially possible that metal shavings/dust could intermittently bridge the two contacts. Probably unlikely. Not impossible in my view. The cover isn't cosmetic, there is no reason for cosmetics in this application.
Yes, fluid will get in; no question about it. The piece of plastic is more like an awning than a roof. Fluid can come in from below.
I share your anxiety about metal shavings collecting on the electric parts. To that end, I glued the plastic piece back together and slid it back into place. (I had not previously appreciated that it sits in grooves, and the piece itself clicks in to position.). For good measure, I glued it in place. It should be many times more secure than the other un-fortified ones.
My speculation is that the part is designed for ATF to fill the cavity, but then very little fluid will be exchanged. The awning will help to keep the little pocket of ATF relatively undisturbed.
I invite anyone with proper expertise to correct me.
I don't think the ATF gets high enough to fill that. Wouldn't make sense, as fluid with a lot of metallic particles suspended would cause a short circuit. Your fill level tube in the pan is what, about 1.5" tall?
y3/8n2 is the rear sensor! The one you say looks fixed. To me, it looks damaged. Can you post a close-up?
Quick update: The car is back on the road with a "fixed" TCU (now for the second time, though I have my doubts whether it was a separate new fault, or in reality a return of an old fault that should have been covered under the original repair's "lifetime warranty"), a complete ATF replacement, and cleared transmission codes. (Here's a quick tip: Since, in California, loaner OBD scanners are not legally allowed to clear codes, a decent workaround is this: go to a parts store that also has a service bay (like, for instance, PepBoys). If you ask to borrow the OBD scanner from the service department (and not the parts counter), they will loan you a fully-functional scanner which will read and delete codes.)
My wife couldn't be happier.
To anybody reading this thread and wondering whether the repair is a suitable DIY project: I say, unequivocally, YES!
In fact, I think that repairing the TCU itself is probably a DIY project. I see that the cylindrical consoles are available on Ebay, and instructions are available on youtube. They require soldering three non-microscopic contacts. The original repair was nothing more elegant than the handiwork of a regular Lowe's/Home Depot customer--and would have embarrassed a regular Radio Shack patron. (I was sheepish about the entire project, and--even now--I suppose I obtained some value from letting "the pros" do the soldering. Had the repair failed, I would have had to always question whether I had bungled the TCU repair, had I done it myself. Additionally, I sent it to the same shop that had repaired it once, with at least some hope (maybe even expectation) that the work would be done under warranty. My situation, then, is a little bit different. But I would absolutely recommend that any competent do-it-yourselfer embark on the entire repair him- or herself. I have also been led to believe that many independent shops can now flash ("recode" or "marry") TCUs to the car, so it is now less and less the case that a TCU error is a) the car's death sentence or even b) a fault exclusively fixed at the dealership (despite Mercedes Benz continuing to classify the TCU as a "theft-relevant" part).
Thanks to the forum members for their help. And best of luck to anybody who encounters the problem in the future.
P.S. I can't see the pictures I had posted earlier in the thread. Is there an obvious reason for that (like, they expire after a certain amount of time)? I'm using the same browser I ever did.
Last edited by wukinpanub; 05-21-2021 at 03:05 PM.
Quick update: The car is back on the road with a "fixed" TCU (now for the second time, though I have my doubts whether it was a separate new fault, or in reality a return of an old fault that should have been covered under the original repair's "lifetime warranty"), a complete ATF replacement, and cleared transmission codes. (Here's a quick tip: Since, in California, loaner OBD scanners are not legally allowed to clear codes, a decent workaround is this: go to a parts store that also has a service bay (like, for instance, PepBoys). If you ask to borrow the OBD scanner from the service department (and not the parts counter), they will loan you a fully-functional scanner which will read and delete codes.)
My wife couldn't be happier.
To anybody reading this thread and wondering whether the repair is a suitable DIY project: I say, unequivocally, YES!
In fact, I think that repairing the TCU itself is probably a DIY project. I see that the cylindrical consoles are available on Ebay, and instructions are available on youtube. They require soldering three non-microscopic contacts. The original repair was nothing more elegant than the handiwork of a regular Lowe's/Home Depot customer--and would have embarrassed a regular Radio Shack patron. (I was sheepish about the entire project, and--even now--I suppose I obtained some value from letting "the pros" do the soldering. Had the repair failed, I would have had to always question whether I had bungled the TCU repair, had I done it myself. Additionally, I sent it to the same shop that had repaired it once, with at least some hope (maybe even expectation) that the work would be done under warranty. My situation, then, is a little bit different. But I would absolutely recommend that any competent do-it-yourselfer embark on the entire repair him- or herself. I have also been led to believe that many independent shops can now flash ("recode" or "marry") TCUs to the car, so it is now less and less the case that a TCU error is a) the car's death sentence or even b) a fault exclusively fixed at the dealership (despite Mercedes Benz continuing to classify the TCU as a "theft-relevant" part).
Thanks to the forum members for their help. And best of luck to anybody who encounters the problem in the future.
P.S. I can't see the pictures I had posted earlier in the thread. Is there an obvious reason for that (like, they expire after a certain amount of time)? I'm using the same browser I ever did.
Thanks for sharing this journey with us, i am so glad i came across this post, i also live in Van Nuys and having the same issue with a 2011 E350 I just bought, there's a whole story behind this car but I will leave that for another time.
My car doesn't get into limp mode, but I noticed the RPM needle goes up and down while driving at a steady speed, from time to time I can feel the transmission gets stuck on 5th gear and stays there longer than it should then I feel a big jump, but this is very random.
just to be able to read the error codes but was not able to see any transmission related codes.
I am ready to get under the car and start dropping the contact plate just to see what's going on, as I mentioned I just bought this car around 4 days ago and when I drove it for the first time I did not notice the issues i am seeing now. Would you mind sharing the private shop you used to rebuild the contact plate, I was going to take it to my mechanic tomorrow but he is a Volvo mechanic specifically so I rather take it somewhere else where they would have a little more experience with these type of cars.
I honestly do not want to end up spending thousands of dollars in trying to fix whatever problems this car has, but I have repair BMWs and other cars in the past, i am no expert but I love getting my hands dirty and a good challenge.
Thanks in advance, hope you can share the shop's info so i can make an appointment and take my car in.
The shop that I dealt with only repairs the TCUs. They neither remove nor reinstall the conductor plate. (Additionally, I am still trying to figure out whether they replaced a second unit on the TCU this time. From everything I can see, it looks I paid another charge to have them simply replace again the same seonsor they replaced in 2015, which should have been covered by their lifetime warranty.)
I called them and the technician seemed very knowledgable. I would recommend you let them have a crack at your car, then be sure to tell us your experience.
The shop that I dealt with only repairs the TCUs. They neither remove nor reinstall the conductor plate. (Additionally, I am still trying to figure out whether they replaced a second unit on the TCU this time. From everything I can see, it looks I paid another charge to have them simply replace again the same seonsor they replaced in 2015, which should have been covered by their lifetime warranty.)
I called them and the technician seemed very knowledgable. I would recommend you let them have a crack at your car, then be sure to tell us your experience.
Good luck.
thanks for that info, can you share the info for the shop in Van Nuys, I can take the conductor plate down myself, that won't be a problem, I will also give the shop in Santa Monica a call tomorrow morning and schedule an appointment as well.
05-01-2021, 01:25 AM
