Nox sensor faulty C200 petrol

[toneil461]

Hi,

I know its common knowledge that the NOx sensors on Merc W205 diesels have been failing at an alarming rate, my previous 2016 C220d was on its third set (incl originals).
My current 2016 Merc C200 petrol now requires a new NOx sensor thankfully it's got just one.
The question is; The Merc W205 petrol vehicle is there a common failure of Nox sensor??

 

[OldskoolRS]

I don't think it's as common on the petrol models. What I will say is that I replaced mine in error (it turned out to be another sensor that was the issue) and it wasn't a genuine MB part, but worked well. When I eventually replaced the correct sensor (o2 post cat) only a genuine MB part sorted it rather than the cheaper Bosch part I tried at first. Many on here will tell you that you should only fit genuine MB parts, but in my case that was 50/50 as the much cheaper Nox sensor is still on my car as I haven't got round to putting the original MB one back on since I sorted the o2 sensor fault.

The Nox sensor was pretty tight, but managed to get it out after I took off the undertray panel enough to reach it (or rather the connection box which is attached to the underside of the car floor). I can search for the part I fitted and provide a link if it's any help?

 

[toneil461]

I don't think it's as common on the petrol models. What I will say is that I replaced mine in error (it turned out to be another sensor that was the issue) and it wasn't a genuine MB part, but worked well. When I eventually replaced the correct sensor (o2 post cat) only a genuine MB part sorted it rather than the cheaper Bosch part I tried at first. Many on here will tell you that you should only fit genuine MB parts, but in my case that was 50/50 as the much cheaper Nox sensor is still on my car as I haven't got round to putting the original MB one back on since I sorted the o2 sensor fault.

The Nox sensor was pretty tight, but managed to get it out after I took off the undertray panel enough to reach it (or rather the connection box which is attached to the underside of the car floor). I can search for the part I fitted and provide a link if it's any help?

Thank you for your reply its very much appreciated. I didn't think it was common on petrol models either, although the Indy said they'd done a few. The Indy I use has XENTRY diagnostics which identified the NOx sensor bringing on the EML (as did my Icarsoft tool), they are going to replace the sensor next week using genuine MB part.

It's a part I could easily replace but my diagnostic tool will not carryout adaptation of the new sensor hence help from Indy!

Not sure what model and year your vehicle is but when you replaced your NOx sensor did you have to carryout 'adaptation/programming of your new sensor or was it just plug play? Is the post cat sensor not the NOx sensor / O2 sensor combined?

 

[OldskoolRS]

I've got an iCar soft as well, though I misread which sensor was at fault, hence buying the Nox one, partly because my brother in law had his replaced around the same time and I stupidly got it in my head it was the same issue. (His is also a petrol C200). I just fitted the non MB Nox sensor and didn't do any adaptations, just reset the error code and that was it. However, the o2 sensor error code was really the issue, so that one took a while to sort as I initially replaced that with the Bosch part, then eventually a genuine MB part more recently which has now sorted the error code.

I had planned to refit the original MB Nox sensor since it wasn't faulty, but have been busy doing other jobs on the car and elsewhere around the house/garden(!). My MPG has improved since I replaced the o2 sensor with the MB part, but still not as high as it used to be, hence thinking I'll try refitting the original Nox sensor. Maybe I should have done some adaptation step when I fitted the replacement Nox sensor, but no error codes show now.

 

[toneil461]

I've got an iCar soft as well, though I misread which sensor was at fault, hence buying the Nox one, partly because my brother in law had his replaced around the same time and I stupidly got it in my head it was the same issue. (His is also a petrol C200). I just fitted the non MB Nox sensor and didn't do any adaptations, just reset the error code and that was it. However, the o2 sensor error code was really the issue, so that one took a while to sort as I initially replaced that with the Bosch part, then eventually a genuine MB part more recently which has now sorted the error code.

I had planned to refit the original MB Nox sensor since it wasn't faulty, but have been busy doing other jobs on the car and elsewhere around the house/garden(!). My MPG has improved since I replaced the o2 sensor with the MB part, but still not as high as it used to be, hence thinking I'll try refitting the original Nox sensor. Maybe I should have done some adaptation step when I fitted the replacement Nox sensor, but no error codes show now.

Thank you for the info. Mine goes into Indy next Thursday to have the NOx sensor replaced with genuine MB one. Hopefully (fingers crossed) that'll sort it.

 

[TC350]

Thank you for the info. Mine goes into Indy next Thursday to have the NOx sensor replaced with genuine MB one. Hopefully (fingers crossed) that'll sort it.

I do hope that all will be fine, but ...

I've had NOx sensors replaced by Mercedes three times on my petrol C350, and none have lasted long. I now spend a couple of minutes every year or so erasing the "faulty NOx sensor" code when it pops up using my cheap OBD2 Scanner. My theory is that if it's only showing as faulty once a year, there's probably nothing wrong with the sensor and it's just too tight a limit set in the software that's occasionally reached.

 

[toneil461]

I do hope that all will be fine, but ...

I've had NOx sensors replaced by Mercedes three times on my petrol C350, and none have lasted long. I now spend a couple of minutes every year or so erasing the "faulty NOx sensor" code when it pops up using my cheap OBD2 Scanner. My theory is that if it's only showing as faulty once a year, there's probably nothing wrong with the sensor and it's just too tight a limit set in the software that's occasionally reached.

I hope it'll be a fix also!
I've cleared mine a few times previously which lasted a while. However now the EML comes back on after a couple of miles after clearing, hence the replacement.