I fixed my NOx sensor problem after spending a few hundred pounds; if your engine management light is on, it could be because of this.
After plugging in my wife's 2018 C220d, I saw that the NOx sensor 2 (cylinder bank 1) code P229F91 was to blame. I purchased a replacement part on eBay for £94 and installed it. The light went out for a few days, but then it came back on.
I was informed that in order to inform the ECU that I had replaced the part, so I made an appointment at MB. After spending £120, they informed me that the light was turned off but could be turned back on because the part wasn't authentic. To my dismay, it turned back on. So I contacted the eBay seller from whom I bought the sensor and explained my situation. He assured me that he had sold hundreds of these sensors without a hitch, but he explained how they work and suggested that I check the voltage of my battery while the car was off. I did so, and he was certain that this was the problem. I spent £180 on a new battery, got the light cleared, and now it's been a month and still no light.
You live and learn; the moral of the story is that MB isn't all-knowing; they never fixed this problem with their super OBD machine, and the guy on eBay fixed it. It may not have been the sensor at all. First things first: make sure the battery voltage is correct.
With any luck, this will be useful to someone.
Troubleshooting the NOx sensor
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MercedesFan2022
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Low battery voltage does appear to affect Mercedes to a significant degree.
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Lucy_Wilson2002
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Although they cleared the light, Mercedes warned that the warning light might trigger again and that the part wasn't authentic, so they may have done their best to resolve the issue.
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Thomas_Green78
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I know I've said this before, but after five years of using this strategy, I see no reason to change it.
An inexpensive OBDII scanner allows me to erase the code that indicates a sensor failure approximately once a year when the EML light comes on. A miraculous self-healing mechanism ensures that it will not trouble me for another twelve months.
In my opinion, the sensor briefly registers a NOx level slightly above an overly strict specification, but it quickly clears up. This cannot be accomplished with the current software.
An inexpensive OBDII scanner allows me to erase the code that indicates a sensor failure approximately once a year when the EML light comes on. A miraculous self-healing mechanism ensures that it will not trouble me for another twelve months.
In my opinion, the sensor briefly registers a NOx level slightly above an overly strict specification, but it quickly clears up. This cannot be accomplished with the current software.
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godisgreat
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Battery issues have been the most common with my SL; my vehicle is very sensitive to this.Everything is fine; I simply use it more frequently. (Hope everything works out)
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John_Doe1975
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Good day. It seems like a downstream sensor was necessary. Do you happen to have the part number for the upstream sensor on hand? I'm having a hard time tracking it down. Somebody informed me about A0009053503 and A0009053603. You should make note of the vendor's name because he appears very knowledgeable. I have been searching in vain for the correct one, so any advice would be greatly appreciated. I am grateful.