NOx - Understanding How Many Of Us

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T5R+

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Seeing a number of threads from fellow posters over this issue. Wonder if worth trying to understand how widespread and consolidating onto one thread to share how many of us
  • are being
  • have been
affected by this issue?

Also, seems that MB/dealers have a very inconsistent policy to resolution. Suspect sharing of experience could save someone £100s or £1000+

So.........my AdBlue restricted message has just appeared. Rang dealer and my (preowned) car has never had the diesel emissions software update. Apparently, it was due one but must have been missed off the list.

Just picked some threads at random from our site never mind other forums.










 
Mines currently in with MB as we speak, dropped it of this morning after waiting almost a month due to COVID-19. I’ll let you know the outcome two of my friends put there preowned vechicles in with MB and one got a goodwill gesture the other it cost £345. Seems MB have mixed views on it and it’s dealt with by individual cars.
 
Mods - could we leave in General to get some initial traction? I am guilty as most, as seldom venture into "Engine".
 
Just had a phone call telling me that my NOx sensors have been replaced free of charge by Mercedes and that they won’t be charging me for the replacement or diagnostic carried out however there was a blockage in my AdBlue injection funnel so that had to be sorted. All in £121, very happy with MB for sorting this for me and hopefully hear of other positive outcomes on this.
 
This is one of the things putting me off changing my petrol CLS for a lightly used diesel E/GLC/GLE. Will follow this thread with interest.
 
Hi
Both mine were replaced FOC, though only one had failed, this was before the software update had been done, E350CDI Cabriolet 65 plate, 265BHP Engine, Mercedes approved used out of warranty by approx 3 weeks, no mention of me having to foot the repair or even the diagnostic.
The one NOX sensor failed no more than a 100 miles after service (approx. 52k miles), Engine light on, for a short time with low Adblue message, then message changed to a countdown till engine wont re-start.
I think there is a combination of a defective batch sensors from build, software incompatibility with old sensors causing them to fail prematurely, depending on engine type, specific engine numbers, build dates, bring in the dealers who go out of their way to get goodwill payments, cars, all appear to give MBs apparent inconsistencies in how each car/customer is dealt with.
 
BTW:

I had a talk with one of my friends working as a MB mechanic and he happend to mention NOx-sensor failures,
particularly the rear one. One of his customers have had repeated failures and replacements.
Eventuallay, he learned that the problem was accumulation of condensated water in the (cold) exhaust system

When driving, the NOx sensor is heated by its supply voltage, and when the driver makes a sudden movement
the cold water hits the sensor and destroys it.

The advice from MB support was to drill a small hole ~3mm at the absolute lowest point
of the exhaust system where water could accumulate. Then as the next step, the car should be driven
and forced to make a catalyst rejuvenation cycle, burning away any residual water in the system.
 
Is it just affecting add blue cars ??
No. They failed on my C350 petrol last year (when it was 7 years old).

MB agreed to knock £1,000 off the £1,200 repair cost. I’m confident that they still did this on my car that was 4 years out of warranty because it was low mileage (30k), one owner and full MB service history. The extent of their goodwill must be down to several factors, which is why there are so many different stories.
 
BTW:

I had a talk with one of my friends working as a MB mechanic and he happend to mention NOx-sensor failures,
particularly the rear one. One of his customers have had repeated failures and replacements.
Eventuallay, he learned that the problem was accumulation of condensated water in the (cold) exhaust system

When driving, the NOx sensor is heated by its supply voltage, and when the driver makes a sudden movement
the cold water hits the sensor and destroys it.

The advice from MB support was to drill a small hole ~3mm at the absolute lowest point
of the exhaust system where water could accumulate. Then as the next step, the car should be driven
and forced to make a catalyst rejuvenation cycle, burning away any residual water in the system.
That sounds like a good explanation of the cause. Not only did my NOx sensors fail, but the exhaust pipe had a rusty crack/hole appear that could well have started from the inside.
 
Mine (a 2015 E220d W212) is in at the moment with the engine light on. The recall was done just over 4 weeks ago and the engine light came on within 4 weeks although only 5 trips as the car has stood a lot during lockdown.

I only noticed the ECU, transmission (VGS) & SCR software versions change after the update.

The current error the car went in for as shown on an iCarsoft is a P229F / NOx Sensor Circuit Range / Performance Bank 1 Sensor 2.

I did read some people were getting line item 30o added to their data card after the recall which meant the correct new NOx sensors were supplied and fitted but my car still does not show this a month on (Two sides of the same coin)

Software versions from Xentry for reference (in case it ever helps anyone).

Pre the recall:

Screenshot 2020-12-01 at 13.50.18.pngScreenshot 2020-12-01 at 13.50.29.png
Screenshot 2020-12-01 at 13.53.13.png

Post recall:

Screenshot 2020-12-01 at 13.54.49.png
Screenshot 2020-12-01 at 13.54.56.png
 
Last edited:
A month ago, had the dreaded
  • Engine Management Light
  • Adblue message informing me that car will be undriveable in 486miles
So had no choice but to park it up after 3 days (now at 124 miles until “will not start”, as drive approx. 120miles/day) and wait for a month until MB could get it into the workshop. Luckily have access to other cars.

Month later drop off the car later whilst the “service booking agent” informs me that software change will fix the issue and they will charge. I politely point out that suspect that it “will require a couple of NOx sensors as well as diagnostic and then software update as is a documented fault. Suggest he should inform his manager that may have a prickly customer on their hands”.:rolleyes: Naturally, the usual fiasco ensued when at 4:45pm each day they would tell me that “it requires a part, we do not have it in stock, but we will get it next day”. 5 days later collected the car.

Have I been lucky or well informed (due to this forum and my effort to be pre-armed with the necessary information) over the fact that I have had to pay £0. Why do I say this – the car is a 2015 350CDi which I purchased 3 years ago in a blind buy privately from Ireland and have carried out servicing privately, so effectively no FMBSH.

At the purchase time did call MB to check if this car required the fuel related software update but was told “no”. When the issue arose last month, checked again only to be told “yes” it is on the list.

So, to others who are experiencing issues – it is worth speaking with MB rather than paying out £100s/£1000s even if your vehicle is out warranty, lacks full MB service history or they tell you it was not an affected vehicle.
 
Its threads like this and my local garage mechanics who all drive petrol cars, that make me glad I steered away from buying diesel in spite of the mpg.
 
I have posted regarding this issue before, any way long story short. I have hade the NOX sensors replace 3x now all under good will, latest one today, no grief at all from dealership, in fact a pleasant experience. I just wonder why there are so many problems why has not MB actually rectified the cause, rather than paying out for labour and parts etc Not only that but the continued unreliability of the sensors somewhat diminishes my faith in the car.
 
Its threads like this and my local garage mechanics who all drive petrol cars, that make me glad I steered away from buying diesel in spite of the mpg.
In 50 years of motoring I’ve never owned a diesel car, and don’t intend to. But the NOx sensor issue isn’t unique to diesels, my C350 petrol has also had them replaced.
 
I also posted this in a similar thread. ML350 63 plate with 102500 miles so well out of normal warranty. Initial quote of £1155 for 2 x Nox sensors was waived and fixed under recall notice to update/amend software. Local specialist wanted £200 more and obviously wouldnt waive. Almost paid $299 on ebay for an OBID plug in which claims to overide the countdown.....be curious if anyone has gone down this route.
 
I'm experiencing the same problem - yellow engine warning light is on and after a Xentry scan I have the fault code: p229f91, which relates to NOX sensors. My car is w212 bluetec 2015 56k miles. I can see this is a very sensible problem with Mercedes cars.
 
Welcome Cris. Assume dealer scanned? Irrespective, you should approach the dealer to see what they can undertake. It appears of late that MB are waking up and completing works mostly FOC.
 

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