Sensor problem NOX sensor

[scotland1]

Hi! New member on here although previous Merc owner. Just wondering how many of us are having what I would consider premature NOX sensor failures. I started getting an EML around 31000 miles(NOX sensor). DTC was read & cleared and the vehicle went for around 750 miles before it appeared again. As time progressed the EML would come on more regularly. until at 37000 miles the infamous AdBlue message xxx miles till engine start not possible came up, co-incidentally after I had filled up the AdBlu tank. I put it into the stealership & the cost for replacing the sensor was £850!! I bought the vehicle with 28000 miles on the clock & within 2 weeks the EML came on indicating a cam sensor fault if I remember correctly. DTC was cleared & the fault has not materialised again. I have had 4 messages telling me that tail lights were non operational when everything was working fine. I verified with MB UK that there were no outstanding recalls for the vehicle. At the dealership I asked about software updates & was told it had one done in June 2020 for the fuel/fuel management system. It would certainly appear in y opinion that this NOX sensor was not fit for purpose & that MB should at least be making some contribution. My previous Merc had done 118000 miles before I had any problem with the exhaust/emissions system which at that mileage was not unreasonable to expect. I intend having this out with MB UK.

 

[zena123]

Scotland 1 .... please keep us informed of yr progress with MB UK !!! Tx

 

[mioba]

Been covered to death. NOx faults esp since dieselgate. If they update emmisions software its more prevalent because there are updated Nox sensors. So you get update, sensors fail and have to shell out for updated sensors.

Some members had then replaced for free, others not and they are not cheap.

Dont ask your dealer is your car is due a recall. they are cluless.

Put your vin in the MB recall page. I checked my W251, it was due a airbag recall. I asked the dealer, no sir no recalls due on your car. are you sure I said as shows on the recall page, sure they said. a month later got a letter through the post saying airbag recall.

 

[scotland1]

Scotland 1 .... please keep us informed of yr progress with MB UK !!! Tx

So far no luck with MB UK, got the stock answer that as the vehicle was out of the 3 year warranty, they would not be making any contribution to my costs. They did fail to answer my question about the reasonable expected lifespan of the NOX sensors so I will be asking questions of them again. I asked the stealership for the faulty NOX module back but they simply said that it had to go back to MB & that they got some sort of allowance for this. Trying to find out where the diesel software upgrade was done in 2020 & if any components were changed. Have not finished with MB yet as I am trying to get answers but they have been struggling with these AdBlu systems for nigh on 10 years & in many cases the customer is having to pay. Will be telling them that I am contacting the Motor Ombudsman & the DVSA as I consider that the number of vehicles having these problems is down to what is a system that is not fit for purpose & by default means that the vehicle is not fit for purpose.

 

[RAMG85]

Hi guys! I’m new on this forum but a Mercedes’ lover since a child! I own a w212 FL 220 bluetec AMG night Ed since dec 2018. Was imported from UK with 72000km on the clock. On the service history appears a NOx sensor was changed at 40000km. Last month I brought the car to dealership in Dublin for software update recall. EML was on as well but went off after update. Next day it came on dash again and yesterday I brought the car back to dealership. Diagnosis was free, it showed that both NOx sensors are gone and they said will try to replace them for free (goodwill)! Monday/Tuesday they will come back with an answer!

 

[zena123]

Scotland1 said: "faulty NOX module... they said that it had to go back to MB & that they got some sort of allowance for this" ... OK if you haven't been billed for it. And even if for purposes of research, MB must by now surely have had enough returned .... must be a mountain of them by now ! That is, ..... if they are ever really sent back to MB.

 

[zena123]

Mioba said: "you get software update, sensors fail and have to shell out for updated sensors". Markjay made a similar comment in April 2021.

Following this discussion as I have EML/NOx sensor issue again. Will check with dealership to find out when they did the update.

 

[Joelle1999]

Hi! New member on here although previous Merc owner. Just wondering how many of us are having what I would consider premature NOX sensor snaptube vidmate failures. I started getting an EML around 31000 miles(NOX sensor). DTC was read & cleared and the vehicle went for around 750 miles before it appeared again. As time progressed the EML would come on more regularly. until at 37000 miles the infamous AdBlue message xxx miles till engine start not possible came up, co-incidentally after I had filled up the AdBlu tank. I put it into the stealership & the cost for replacing the sensor was £850!! I bought the vehicle with 28000 miles on the clock & within 2 weeks the EML came on indicating a cam sensor fault if I remember correctly. DTC was cleared & the fault has not materialised again. I have had 4 messages telling me that tail lights were non operational when everything was working fine. I verified with MB UK that there were no outstanding recalls for the vehicle. At the dealership I asked about software updates & was told it had one done in June 2020 for the fuel/fuel management system. It would certainly appear in y opinion that this NOX sensor was not fit for purpose & that MB should at least be making some contribution. My previous Merc had done 118000 miles before I had any problem with the exhaust/emissions system which at that mileage was not unreasonable to expect. I intend having this out with MB UK.

Welcome to the forum

 

[zena123]

Scotland1 - I see you're in London. Dealership I'm with is Colindale: they replaced downstream NOx sensor in 2020. A friend's garage ran a diagnostic last week (EML was on) & it's come up with the same NOx sensor fault as previously (P220F-77). I contacted Colindale who, naturally, say they need to do their own diagnostic (£170+) ... if it's the same sensor, then they may replace & diagnostic 'may' be FoC. If it's not that sensor, I'll have to fork out for the diagnostic + new sensor as I'm outside the 3-year warranty. I'm thinking it may be worth peace of mind to travel down to Portsmouth as I hear there's a v. reliable Indie there ....

 

[Smith1]

Hi! New member on here although previous Merc owner. Just wondering how many of us are having what I would consider premature NOX sensor failures. I started getting an EML around 31000 miles(NOX sensor). DTC was read & cleared and the vehicle went for around 750 miles before it appeared again. As time progressed the EML would come on more regularly. until at 37000 miles the infamous AdBlue message xxx miles till engine start not possible came up, co-incidentally after I had filled up the AdBlu tank. I put it into the stealership & the cost for replacing the sensor was £850!! I bought the vehicle with 28000 miles on the clock & within 2 weeks the EML came on indicating a cam sensor fault if I remember correctly. DTC was cleared & the fault has not materialised again. I have had 4 messages telling me that tail lights were non operational when everything was working fine. I verified with MB UK that there were no outstanding recalls for the vehicle. At the dealership I asked about software updates & was told it had one done in June 2020 for the fuel/fuel management system. It would certainly appear in y opinion that this NOX sensor was not fit for purpose & that MB should at least be making some contribution. My previous Merc had done 118000 miles before I had any problem with the exhaust/emissions system which at that mileage was not unreasonable to expect. I intend having this out with MB UK.

Almost exactly the same as happened to me. End of last year EML came on (2019 GLC 250) and I got local garage to check code and reset same , it was P229F91 , NOX sensor 2 cylinder bank 1.I contacted MB in Inverness who told me to bring the car up and they would check it out , however they found nothing wrong but said to contact them if it came on again. At this point the car was still under manufactures warranty. End of February and the EML light came back on. I read the code and it is the same again , this time have left it and contacted MB again , is now booked in start of April so will be interesting to see what they say. The “Unable to calculate Adblue level” message is now appearing. The warranty has now just expired but it is very disappointing to have all these issues on a car that has just turned 30,000 miles , surely sub standard equipment being used by MB and not what I would expect.

 

[scotland1]

MB refusing to contribute as car is outwith the 3 year warranty. Hardly surprising that people are deserting to other marques with 5/7 year warranties! They did not even answer my question as to what the expected life expectancy of the NOX sensors is. Will ask them the question again.

 

[zena123]

Apologies for long post: Discussion with MB Service Manager today.

History: July 2020, EML came on & downstream NOx Sensor was replaced FOC under Warranty. (Warranty ended Jan 2021)

Jan 2022, EML came on & dealership had the car today, but were too busy, so will run Star diagnostic tomorrow.

Today, the Service Manager said … If I had “BOUGHT the sensor (replaced FOC as above) from them, the standard 2-year Guarantee would apply” & the sensor would be replaced FOC. BUT a Sensor that has been replaced under Warranty LOSES that 2-year Guarantee if it subsequently develops a fault.

[To quote the Service Manager: “You can’t have a Warranty on a Warranty.”]

Me to Manager: “I booked with Centralised Phone Call System (based at Milton Keynes), who said Diagnostics would be £173 & there should be a 2-year guarantee on the NOx Sensor. Also, if the Diagnostic Fault Code is a repeat of the previous Fault, then they MIGHT waive diagnostic charge AND the sensor charge as ‘a gesture of goodwill’.

Service Manager: “They have given out the wrong information on the phone because they aren’t savvy with what’s going on…. They’ve misunderstood, as YOU don’t have a parts warranty because you haven’t purchased anything. … What we’d do is, if it’s the same fault as before, we’d ask for a gesture of goodwill [from MB]….What we can do is offer that you pay for the diagnostic [£173] and the sensor might be replaced as a gesture of goodwill.” He went on to say: ”It could be that MB will replace the Sensor FOC, but you may need to pay anything from 0-100% as a contribution. Cost of diagnostics is £173 and we would find out what’s wrong…
Me: “So I would pay for the diagnostic and you MAY replace the sensor FOC ?”
Service Manager: “if diagnostic shows the fault is the same as before, then you MIGHT be repaid the diagnostic charge as goodwill gesture"
[*Another garage diagnosed w. Star & found the EML fault IS the NOx Sensor. But Service Mgr says he needs to run his own diagnostic.] Wd be interested to hear if anyone has any views on the above ..

 

[jelder]

Mioba said: "you get software update, sensors fail and have to shell out for updated sensors". Markjay made a similar comment in April 2021.

Following this discussion as I have EML/NOx sensor issue again. Will check with dealership to find out when they did the update.

Hi. I have a GLC 250d with the same issue. Emissions software update was applied following recall, orange engine warning light started coming on, diagnosed as a NOx sensor issue; warning light and faults cleared a couple of times but came back on each time, then in April I got the "AdBlue, Eng. start not possible in 500mi" message and countdown. Car is out of warranty now but I have had it since new and it only has 30,000 miles on the clock

Dealer said I would need "diagnostics" (£144) and they were so busy they could only squeeze me in a couple of weeks later. Following diagnostics they confirmed that it is the NOx sensor which needs replaced. As this is a "known issue" with these cars they agreed to submit a request to MB for a contribution to the repair but came back the next day to say, "the eskulab contribution has been denied" (i.e. MB won't contribute to the cost of the diagnosis or repair). I asked the dealer to carry out the repair ASAP anyway (£644) pending further discussion with MB but apparently they need to order the NOx sensor from Germany, it's been on back order for some time and they can't give any indication of when it might be available, and they won't book in the repair until they have the part.

I assumed that the countdown could be paused or reset but apparently that is not possible, the car becomes inoperable once the countdown reaches zero. So my family has effectively been without a car for two weeks now.

I checked with the dealer today and they simply replied that the NOx sensor is "still currently on order with no ETA". I see from one of the many similar threads here that it took someone over a year to source a new NOx sensor. It's difficult to make alternative arrangements when you don't know whether your car will be out of action for a couple of weeks, months, or a year or more.

The dealer did encourage me to take the issue further with MB directly. They confirmed (as I know from this and other forums and a MB indie specialist) that this is a "known issue" with the GLC, in their experience MB sometimes do cover repairs and sometimes don't, and that there had been a second emissions control system recall issued to replace the NOx sensors on some GLCs but not apparently for mine. I emailed and wrote to MB Customer Services last week, hopefully they will be more sympathetic at the second time of asking.

It beggars belief that a £42,000 car has an expected life of 30,000 miles and then simply shuts down, with MB not only denying all liability but not being able to provide parts for a repair.

 

[zena123]

Mine is being replaced (second time!) next week. Dealership wouldn't commit to a date until sensor came in. That took approx 1 month. Thanks to Mioba's post, I took steps to find out if Dieselgate software update has been done (it has) & then requested dealership to ensure that the replacement sensor is V.3 (as advised by Mioba). Hoping all goes to plan. Very sorry to read Jelder's post : he makes his point very clearly in his last paragraph. Seems unjust that he has to fork out for total cost, incl. Diagnostic AND lose use of car for unspecified time. Jelder: did you take out a Service Plan w. Mercedes ??

 

[jelder]

Jelder: did you take out a Service Plan w. Mercedes ??

Hi Zena123. Sorry to hear you're having the issue too, and for a second time no less. That's good it "only" took about a month to source the part, my dealer sounds like they're expecting it to be longer.
I had a MB service plan for the first three services, then had one or two at a local specialist indie (recorded in the online service log) and then went back onto a MB service plan for the last service and the next one.
MB customer services have replied to my direct contact to say that the dealer will be back in touch with me and they can't say anything further.

 

[zena123]

Hi Jelder: My dealer also gave impression it cd be 6 months-1 year to get the part. So hopefully yours will be a month or so. Dealership also had no answers for if an Ad-Blue warning appeared (meaning, like yours, car off the road). Doesn't alter the fact that it shouldn't be happening. [NOx sensors apparently have a 2year guarantee - you may want to check that out at your dealership, just in case your replacement one proves defective in a year or so's time !]

 

[zena123]

Update today on NOx sensor replacement : car went in today (seems quite a few were there on 'recall') so it will be 'done' tomorrow a.m. Mioba said (in another thread, I think) the sensor ought to be V3: the vehicle has had its Dieselgate Software update. I made Mioba's point to the garage : their representative had no knowledge of a V3, let alone a V2, and said they were installing 'the latest model'. They produced it & I attach pic of label & box. Is anybody able to verify that this is V3 (or later)?? (It's just a thought that s.o. may know .... Garage, of course, covered itself & said, if EML stays on after the NOx sensor is changed, then that cause may be another issue & will need another diagnostic .... : which is, I guess, what I expected them to say. Grateful, as always, that all you guys are out there & willing - & interested enough in these issues - to offer your opinions.

 

[jelder]

Good to see that someone has some progress. My dealer did not, as MB Customer Services promised, get in touch with an offer. Their phone number rings out until it disconnects. I called MB Customer Services again after a week, they said they'd chase the dealer and be back in touch within five more days but probably much sooner. Day four now and still nothing from them either. Meantime there's apparently still no ETA on the NOx sensor parts. Car still sitting useless. Seriously unimpressed with Mercedes.

 

[Smith1]

Diagnostic check carried out which confirmed faulty NOx sensor , diagnostic check and replacement both covered by Mercedes , great service from Mercedes at Inverness but still disappointed that these issues are still happening to newer vehicles, we’ll see if any issues crop up with the other sensor.

 

[chardonbleu]

Eight weeks now since I paid the “diagnostic fee” and the NOx sensor was ordered for my GLC, no sign of it becoming available. Last update was a text from the dealer three weeks ago saying they’re awaiting the part still.

In the meantime we have been eking out the 500 mile countdown saving the car for emergencies. It finally expired this week, we parked the car near the house and it’s dead now.

MB CS insisted that the dealer would be in touch with me with an offer, but there’s been total silence from the dealer. After a while MB CS suggested that the dealer would be offering me a 50% contribution to the cost of the NOX sensor. They say they can’t tell me when the part might become available.

MB CS also said they would not consider providing a courtesy vehicle nor reimbursing costs incurred by me due to the fault and not being able to use the car. They added that they don’t even consider there’s a problem with the vehicle until the 500 mile countdown reaches zero and the car becomes totally inoperable. Their advice to me was to run down the 500 miles ASAP, phone Mobilo assist and get the car recovered to the dealer. At that point they would acknowledge there is something wrong with the car, but not before. A patently absurd position but that’s what they told me.

I will probably call Mobilo assist tomorrow and ask for the car to be taken to the dealer as MB suggested. I’m sure the dealer will be delighted to store my car whilst waiting for the NOx sensor part, although perhaps they will then speak to me. I wonder how my request for a courtesy car will go down. I see that Mobilo offers a replacement car for up to three days pending a repair being completed. Not sure how that sits with MB not being able to provide parts for months.

I was previously quite happy with my GLC and would have been replacing it at some point with another MB, but I’m now quite tempted to just sell it as soon as it’s fixed and never touch a MB ever again. It’s been an interesting way to treat a previously loyal repeat customer and advocate for the brand.