CLK Group

I purchased a CPO 2008 ML320 CDI 4Matic with 21,000 miles in January. Vehicle is also under original warranty.

Three weeks ago while out, I started the engine and transmission was in Limp Home Mode. Shut off the engine for 5 minutes and restarted. This time the Check Engine light came on but was able to drive OK. The CE light stayed on for the rest of the day and part of the next but trans shifted fine.

CE light went out but brought in to dealer on their recommendation. The technician found an ‘incident’ notation but no actionable error codes. They attributed it to a ‘glitch’. Drove it home and all has been OK.

Today as I exited the freeway and tried to kick down the transmission to get over three lanes, the trans acted like it was stuck in 7th gear. I turned off into a side street and then found that while in Drive, the vehicle was not accelerating even though the RPM’s were up. I placed it in Park, then into Drive. The trans engaged with a noticeable ‘clunk’. No error codes or lights in cluster. Reached destination and drove home about 50 miles with no further issues.

I’m calling the dealer on Tuesday to see what they say – may want me to bring it in to see if any error codes did register.

Anyone have a similar situation happen?

eminnet

Check the trans/shift battery.

CLK Group

Took the ML in this morning to the dealer. The computer again showed an 'incident' but no actionable error codes. They decided to keep the vehicle and do some additional trouble shooting. They are also providing MBUSA with both reports to see if they can provide some guidence.

Dealer gave me a 2011 GLK350 as a loaner :^)

C43AMG

Ask for the updated tranny software to be downloaded as well.

mandino

Keep us posted on the outcome. Some of my typical issues:
- - Erratic shifting. Some days it is smooth, some days it takes forever to shift from 1-2-3. It shifts up around 3000rpms then once in 3rd gear it downshifts all the way to less than 2000rpms and in a harsh manner.
- - After slowing down to make a turn I hit the accelerator and the car chokes up like it is about to shut off, then finally shifts and then wants to take off


Been to 3 dealers, either they cannot replicate the issues or they simply perform a software upgrade. This works fine for about a week (if that) and then the shifting issues return…..


what to do???????

C43AMG

I would keep all documentation in regards to the symptoms and diagnosis.In the event you have a "out of warranty" problem you can at least have documentation that the issues were identified while under warranty and corrective action was noted.

mandino

C43AMG,
Oh yeah, without a doubt. I keep ALL records/receipts.


I just came across a post from you in which you stated your ML was flat bedded away due to transmission failure. Is everything good now? What happened, if you can share?

Thank you,
M

C43AMG

They said it was a drop in fuel rail pressure.The truck started right up and ran fine for the $tealership the next day.I let them keep it for 2 extra days and let the service advisor take it home in case any "issues" happened.He stated as long as I kept my paperwork and it was documented they would "go to bat for me" in the event that it happens again or proves to be a costly out of warranty repair.

mandino

wow, "a drop in fuel rail pressure". never heard of such a thing. lol. well hopefully it does not happen EVER again.

Thanks,
M

CLK Group

Picked up the ML from the dealer this morning. 1 1/2 pages of diagnostic checks for all electrical components connected to both the fuel delivery and transmission. Check on the 'conducter plate/valve body' was negative.

'Newer software found. Install newer software for CDI and Etc. code control units. Clear fault codes. Perform road test. No fault appeared. Normal operation noted'. So apparently the latest software version was not already installed.

OK. I drive about 50 miles and come to a stop sign. When I give it throttle the RPM's go up but the ML feels like it's in 7th gear as before. Place it in Park, then Drive. Transmission engages with noticeable 'clunk'. Start to drive away but trans will not upshift - it's in Limp Home Mode again. Pull over, shut off engine for 10 minutes, restart, drive - still in Limp Home Mode, now with Check Engine Light on. I try this three additional times - trans will not reset.

Call MB Roadside Assistance. Wait 1 hour for flatbed truck, then another hour back to the dealer.

Service Manager very apologetic. Tells me it's a 'good thing' that trans is in Limp Home Mode and Check Engine Light on as they will now be able to view error code(s). Will call me this afternoon or Monday with findings and course of action to repair.

Will keep you posted.

CLK Group

Finally picked up the ML today. Three pages of diagnostics and repair. As the vehicle was returned in Limp Home Mode and the Check Engine Light was on, event codes were generated.

After submitting test print outs to MBUSA, MBUSA authorized replacement of both the Conductor Plate and the Valve Body. Dealer did extended test drive of 105 miles with no issues.

Interesting note - Service Manager told me Mercedes will no longer supply the Conductor Plate by itself - must be obtained with Valve Body. Also, per Service Manager, there seems to be a limited number of replacement Valve Bodies - MB requires the dealer to return the old one.

dgiturbo

Within the first 9 months of me owning mine, I had a similar issue. Limp home, check engine and the famous "clunk" that feels like you just got rear end when you stopped valve body issue.
A friend is an MB tech, and he hinted me about the fuel pressure sensor. Apparently, these CDI's can generate tremendous power, so much so that it will destroy the 7G transmission, and the way this power is made is by injecting more fuel. To prevent this, they used a fuel pressure sensor, and programmed an aggressive fuel cut/limp home mapping if it sees the fuel pressure outside of the safety zone. For whatever reason, you, me and several others have found this threshold. Replacing the sensor usually takes care of the issue. (Bad batch of sensors?)

As for the valve body, last time I went by my MB parts guy, he told me that there have been so many claims that MB has gotten really strict and pretty much needs proof from Congress before they will authorize a replacement. (The valve body also houses the transmission computer.)
The clunk downshift when you stop was the computer telling the tranny to go into first gear before the wheel speed = 0. The software update should correct that.

On a good note, I have never had any related issue since. 92000 miles and counting.

jim, dickerson

Maj. Dundee

Jim, the info he supplied is misleading, There is a small battery along side the main battery. But its only function is to supply voltage to the trans. parking pawl so the shifter can be put into neutral so it can be pulled up onto a flatbed.

It has no function with performance or operation of the trans.

flybd5

That threw me off as well. Transmission battery? I was just going to go out to check if I have one when I remembered I sold my Merc two days ago. LOL! I need to do something about that.