NOX Sensors

[zena123]

Car: (C220d W205; Reg: Jan 2018 (Approved Used, bought: 08/2019); now has 23K miles

Briefly (I hope): EML (Engine Management Light) came on at the end of a 4-mile trip in May with a message to stop driving: I rang MB from car and was told it could be "lack of use (Lockdown): take it on a longer run & see if the message disappears over the next 2 days". Next day I ran it up to Northants & back down the M1 & the message came on again half-way. When I rang MB, they said it was a frequent fault & could be due to any number of issues, including hot weather … I should monitor it over the next couple of days.

A car mechanic friend said his garage could borrow STAR for a diagnosis. This showed the Nox sensor causing the EML to light up. They disabled the Nox Sensor and since then I have not been troubled by the EML. Was this the correct thing to have done ?

On 9 July I got ‘an appointment reminder for MB Brooklands (not my local garage - I live in North London) for 9 a.m. on 10th July'. It seemed to be a random text on my phone so I didn’t follow it up - especially as I didn't see it on my phone till after the event anyway. But, in retrospect, it may have been an MB follow-up of the Nox issue.

Today a post on this forum (great Forum !) makes me wonder if the disabled NOX sensor will be picked up as a fault at next service ('A', due this month) & cost me a fortune to repair/replace. My MB warranty lasts till Jan 2021. I am not on a Service Plan, though am considering it as MB are apparently offering a reduction currently.

I suppose my immediate questions are: (1) are working Nox sensors essential for an MOT ? (2) can disabling them have other (damaging) consequences ? (3) should I contact an MB garage (or Indie) and try to pursue remedying the Nox sensor(s) under warranty ? – if that is possible. Would also welcome any other advice on this. As previously, tx so much for ongoing help !

 

[dmb007]

Hi Zena,

For point 3 see my post NOx Sensors E400 | Engine

I had problem for 12 months until I used the RIGHT dealer on my 2015 E400 so you should be covered at no cost to you, if failed NOX sensors.

I know its an MOT failure if EML is on.

Not sure about damage to car.

Take Care
David

 

[barian]

I am not sure how a NOx sensor can be "disabled". I suspect that your car mechanic cleared the fault code and it has not reoccurred. In that case it may have been a one-off event or it may happen again. If the sensor is faulty then it should be covered by your warranty, but you will need to make sure that you have the car serviced at the required intervals. If there is no fault showing at the moment then I doubt the dealer will investigate. If it happens again then I would call MB Assist and have them come out and take it from there. As an aside, it might be better not to mention that you have had a (presumably) non-approved garage look at the fault.

 

[zena123]

thank you 007 and barian for your advice, much appreciated to you both !

 

[fifermerc]

I might missing something, but I can't see why, when your car is still under warranty, you would take it first to a garage other than an MB dealer? Having someone else play around with it gives them a potential excuse for refusing a warranty claim.

 

[zena123]

Yes W1ghty, ... I think I'm learning the hard way !

 

[zena123]

Just a thought, following Barian's comment above: (& I'm not sure about the vocabulary to use here) & I assume the fault code was cleared (as Barian suggests) ... is the fault code - & the fact that it has been cleared - recorded on the car & evident if a Star diagnosis is carried out ? Mega tx in advance for your help on this.

 

[tombell]

Bought a 62 Plate Merc ML at the beginning of May. A week ago I got message something like "1,700 miles before AdBlue runs out". I filled AdBlue to the brim. EML light still on. Tried all the tricks on the web to turn it off. No Go. Next day "600 miles engine won't restart". Took it to MB Oxford today. They are getting 2 Nox sensors for the end of the week. They want £1,871.52. and will have to remove exhaust. 3.8 hours
Does anyone have the part numbers for the nox sensors and the adblue tank
Mercedes want £1800+ to sort this problem

 

[tombell]

Mercedes Quote with Part Numbers for replacing Nox Sensors on 2012 ML250 TOTAL £ 1,620.96

Labour 3.8 HOURS £385.70

MA166 520 02 23 NOISE CAPSULE £ 88.50

MA000 905 35 03 104A05 NOX SENSOR £417.00

MA202 490 08 41 108C05 CLAMP £ 10.00

MA000 492 08 81 101D04C SEAL RING £ 5.75

MA000 492 08 81 101D04C SEAL RING £ 5.75

MA202 490 08 41 108C05 CLAMP £ 10.00

MN910143 008 006 102D06C HEXALOBULAR BOL £ 1.40

MN910143 008 006 102D06C HEXALOBULAR BOL £ 1.40

MA000 905 36 03 104A13 NOX SENSOR £379.00

MA002 995 49 02 107E09 PIPECLAMP F EXH £ 46.30

NET £1,350.80
VAT £ 270.16
TOTAL £ 1,620.96