Applies to 2015 ML250. 65K miles. Had the emissions recall installed in February 2021. Started about a month ago where it started to require higher rpms than normal to upshift, and stepping on fuel pedal would not down shift and the downshift paddle did not work, but it did down shift when coasting down/stopping. I initially thought it might be the transmission, but the next morning the car was fine until it warmed up at highway speeds. Oh, and no "check engine light". Took it to my local mechanic and he could not find any old or new trouble codes. And during road test, it ran fine. I filled up the DEF tank in case it was low (I had previously put in full 2.5 gallon bottle, but jut to make sure, I topped it off. It ran fine for a couple of weeks. Last Friday (Dec 17) we drove from Jacksonville to St. Pete FL with no incidents. On the way back this morning, the problem returned about 100 miles into trip. First noticed because at interstate speeds, stepping on the gas - even all the way to the floor - did not appreciably increase speed and transmission would not downshift (kick down nor manually with paddle). And when stopped, it would not shift up until 2500 rpm, but I could force an upshift with the upshift paddle. We stopped for fuel at Bucky's just outside of Daytona Beach, and topped off both fuel and DEF. Car ran fine until we got on I-95, and then reverted to what I fear may be a "limp home" mode. Put my real basic Autel scanner on the car and got $7EC and $7E8 codes and both showed up as P0171 "generic engine - system too lean Bank 1"

Has anyone run into this problem? Or do you have any idea what it could be?

Today was the first time I got a check engine light and why I checked codes. I thought it might be related to Emission Service Campaign 2022100016 which addresses a "software issue impacting operation of the water pump diagnostic" but I have not noticed a higher engine temp during all of this. I'm going to try and get an appointment with my local dealer to take care to the Service Campaign, but I do not rust them at all and am worried they might try to pass this on as a non-warranty issue.

 

Don't you have extended warranty after AEM?
Also get a scanner, who can read MB codes.

 

I believe I have the extended warranty for the emissions system after the recall was done.

And, yes, I need a new scanner. Didn't realize how old this one is...

 

FYI the extended warranty gives you dealer's troubleshooting for free, regardless if the issue is covered, or not.

 

I’m at dealer now. They made me sign a work order that I’d be liable for $200 analysis fee if issue is not related to AEM.

 

What did the work order state? The pulling of codes is free as part of the AEM. Now, if they manually troubleshoot after that and it isn't related to AEM, then yes, you would be liable.

Per your letter for 2015 ML250:

OBD System: the cost of any OBD Diagnostic Scan for malfunctions that trigger the MIL, regardless of whether the malfunction is attributable to a part that is covered under the Extended Modification Warranty, as well as the cost of troubleshooting to determine the reason for the malfunction, but only if the malfunction is determined to be attributable to a part that is covered under the Extended Modification Warranty

https://bluetecupdate.mbusa.com/cont...Disclosure.pdf

 

Check your post-AEM warranty .
I am pretty sure it says free checking regardless the issue, but then my cars run perfect lately so I have no motivation to dig the papers.

 

I am having the EXACT same symptoms on my car with trouble codes p0101 and p0171. I was wondering if your vehicle was properly diagnosed and fixed so that I may do the same.

Cheers.

 

In January 2023, the dealer, after trying to get me to pay US$500+ for draining/refilling labor and full tank of DEF, relented and changed the DEF delivery pump under warranty and did not charge for the labor/fluid. I suspect my email to the dealership GM might have had something to do with it. The car ran mostly fine, though once in a great while, it did go into "limp home" mode , but it reset quickly. In May, I brought it in for NHTSA Recall 22V955 ("Inspect Spare Wheel Well for Water" - campaign number 2023010003) and was advised that there was another service advisory: "Update Transmission Control Unit Software", which was performed and since then I have not had any more issues with the car. The Service Advisor indicated that he felt that this would cure the problem and it looks like it did. The paperwork lists it as campaign number 2021120007. It apparently reprograms the transmission so that it doesn't overheat some sensor which ends the unit into limp home mode because it thinks that the exhaust is out of spec.

So far it looks like problem is solved. Engine runs well, shifts more smoothly than before (except it seems to go into a glitch when coasting down to stop in 2nd gear and you step on gas - it kinda gets confused as to whether it should be in 2nd or 1st) and mileage is better. I've gotten as much as 33mpg on Highway as long as I'm under 75-77, but it rapidly degrades to 28-29mpg once you are over 77mph. Not bad for a 2015 (initially sold in Dec 2014)

Hope this helps.

 

I’ve got a 2014 GL350 and I got this P0171 code today. I also got an error P1863 saying contact plate power open circuit.

What’s weird is I had the occasional transmission limp mode under load before the emissions fix. It’s now much worse though - not sure if this is related to the emissions change or just worsened by it. I had Mercedes under warranty try and reproduce the problem a few years ago and they couldn’t so nothing changed

 

Sorry I have not commented/replied recently.

Here's the update. The car has been running fine around town, with a couple of caveats. However, on long trips, I am now getting a Check Engine Light (CEL) and a couple of times the car ended up in Limp Home Mode (LHM) though it "reset" after a 15 minute shutdown while using a rest area or having lunch. All without any CEL. Now, I am finally getting a CEL with P20EE ("Spark Plug A or B of Cylinder 2 or ECI Ignition Module, Right Bank of Cylinders") and P0299 ("Turbocharger Underboss") per my newly purchased BLKTEC 430 OBD2 reader. The check engine light resets after an overnight shutdown, but the codes remain. I have not had a chance to bring it to a new dealer (I will not ever bring any vehicle to either Jacksonville FL dealers - same owner/different dealer/both incompetent) recommended by my independent mechanic but who is in Daytona Beach, a couple of hours away.

After reading the description of the codes on several web sites, I am inclined to believe that one of the issues may be a partially clogged particulate filter as a result of an incomplete "cleaning", or that there is a faulty NOx sensor that is not effectively and properly treating the exhaust and is causing havoc with the catalyst and/or the DPF. To be fair, I have noticed a slight reduction in power at interstate speeds when accelerating to pass, and a noticeable increase in consumption above 75 mph. I recently was getting 36 mpg from Atlanta to Macon GA, but got only 30 or so from Macon to Jacksonville, though we averaged 33.7 from JAX to ATL on the way up. Does anyone have any experience with blended diesel? I noticed on this trip the Bucees' diesel is now labelled 5% biodiesel.

I plan to get the car to Daytona next week. I'll update the saga after that.

 

Forgot to mention: Around town, the transmission, which was "reset" under campaign number 2021120007 "Update Transmission Control Unit Software", seems to be shifting rougher than before, and it is still having trouble shifting into first when coasting into a stop until the car is dead stopped, and if you step on the accelerator before it comes to a full stop, the transmission jerks into first gear.