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Unfixable Nox sensor issue

Crowey

New Member
Joined
Nov 22, 2018
Messages
7
Location
Cheshire
Car
2015 E350 Coupe
Ive read quite a few of the threads on Nox sensors but still don’t know what to do......I’ve just bought my first Mercedes a 2015 E350 coupe. Only had it 2 weeks. On the day we picked up the car the EML came on, MB couldn’t get the car in for a week so we took it to an independent MB specialist who diagnosed a NoX sensor issue. The dealer we bought the car off arranged for it to go to a independant MB specialist who found a perished seal on the exhaust near to the intercooler. A week later EML came on again and came back A non-specific Nox sensor fault. They changed the adblue and light went off then back on again! Car then went to MB Sheffield by which time the EML has gone off again. They were going to replace the Nox sensor and do software update on a goodwill but can’t do this now as no faults on showing! We are getting car back tomorrow but suspect the light will be back on soon! Any advice please?
 
It could easily still be the NOx sensors that are the problem. If that is the case, the EML will return, in which case take it back. They are a known problem!

Ernie
 
So the dealer identified a NOX fault but didn’t replace the sensor? Id be back at the dealer.
 
No it went to an independent garage for the diagnostic and by the time the car got MB Sheffield the EML has gone off so they said they couldn’t do it as no fault could be detected by them
 
No it went to an independent garage for the diagnostic and by the time the car got MB Sheffield the EML has gone off so they said they couldn’t do it as no fault could be detected by them

I’m surprised as i thought all fault codes were stored in the ECU memory - perhaps MB aren't that sophisticated.
 
Mmm I did think the same, but suspect they don’t want to fix it as it’s not showing as ‘broken’.
Can anyone recommend the best Adblue to use as been told to use ‘good quality’?
 
Can anyone recommend the best Adblue to use as been told to use ‘good quality’?

Isn’t it all the same ?

Mercedes should sell it at the parts counter
 
Not sure, I’ve been told to use a ‘branded’ one, not had an adblue car before so have no idea I assumed there must be cheaper ones that aren’t as good.
 
Don’t Mercedes fill that for you when it gets serviced as well? I read something about the diesel as well think it was on here someone kept getting nox sensor errors when it was on supermarket fuel but changing the fuel stopped them and then when they went back to supermarket fuel it started throwing up errors and they tried this a few times to prove it as well.


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Don’t Mercedes fill that for you when it gets serviced as well? I read something about the diesel as well think it was on here someone kept getting nox sensor errors when it was on supermarket fuel but changing the fuel stopped them and then when they went back to supermarket fuel it started throwing up errors and they tried this a few times to prove it as well.


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Yes I read something about supermarket fuel, I’ve only just got the car so not sure how often I’ll need to put the adblue in, but if it’s done at service then that’s great
 
Mines non adblue so don’t quote me on it but I’m 99% sure they top it up as part of the service as I’ve seen something on my service care plan about adblue. Also pretty sure the car will warn you if it’s running out.

Try Shell diesel and see what happens.

Also Sheffield Mercedes my cars never going back there it went in for warranty work replace fuel filler housing they didn’t even put the sticker on for the tyre pressures after they replaced the part it was stuck to. Tried to tell me I needed to order it from parts, no one returned my calls when I kept ringing to tell them it was on the part they replaced so why didn’t they replace that. It took me 2 weeks to get some from them so I’m going to try Doncaster or Wakefield for my servicing from now on.


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These NOx sensors are a sort of modified two stage lambda sensor one before and one after the NOx filter---- they don't like water vapour so there is also a temperature sensor in the exhaust to stop them switching on before the exhaust reaches the proper operating temperature. There have been several versions of these sensors over time and only the latest ones should be used as the earlier ones can fail quite rapidly. Some sensor recoding is also necessary. There was a thread about this not long ago.
Mercedes customer services ect nox sensor issue
ps the problem isn't unfixable its just you haven't got the car to someone who knows how to fix it properly
 
Instead of Unfixable, I should have said refusal to fix!

Even MB main dealers seem to be unaware or deliberately obtuse :rolleyes: about certain faults. This especially so if the car is [a] out of warranty without a complete MB service history. :(
 
Hi Guys
I need help, I have a fault on my 2014 e220 its only done 45000 miles.
I don’t really do long journeys mainly short trips, I thought it may be dpf, so have added dpf cleaner and filled up with shell diesel, the best one.
The fault is as follows
P008709 the fuel pressure in the system is too low. There is a component fault.
P229F62 NOx sensor 2 (cylinder bank 1) has a malfunction. The signal comparison is faulty.

Can anyone please advise on this

Your assistance will be greatly appreciated.

Thanks
 
The engine management relies on 2 sensors fore and aft of the NOx filter unit where the "bluetec"= urea solution is added. It compares the fore and aft readings to monitor if the NOx filter is doing its job. The likely cause of P229F62 is one or both sensors are faulty.
 
I think that if there is an active fault code, the dealer can get the OK from MBUK to fix things under warranty/goodwill. Without that OK, the costs come out of their bottom line and so are therefore less willing to do the work. Take it in when the EML is on.

The dealer has topped up the Addblue on our C250d as part of the service. On ours, the reservoir nominally lasts for 18,000 miles.
 

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