Code P229F91 E250 Nox sensor
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Junior Member
Joined: Jan 2019
Posts: 20
Likes: 6
2014 E250
Code P229F91 E250 Nox sensor
So my 2014 E250 is running great and running smooth after replacing suspension components, tires and brakes. CEL came on ( code P229 Nox sensor ) so dealer replaced the sensor under the extended emissions warranty.
The car has 131000 miles. The car had the AEM update at 93000 miles so I believe the NOx sensors were replaced at that time. Going forward can I expect the NOx sensors to need replacing every 40K miles or so?
Anything I can do to extend the life of NOx sensors? Great car other than the ongoing battle with the emissions system. My scan gauge keeps tabs on the DPF, now if I can extend the life of NOx sensors !
The car has 131000 miles. The car had the AEM update at 93000 miles so I believe the NOx sensors were replaced at that time. Going forward can I expect the NOx sensors to need replacing every 40K miles or so?
Anything I can do to extend the life of NOx sensors? Great car other than the ongoing battle with the emissions system. My scan gauge keeps tabs on the DPF, now if I can extend the life of NOx sensors !
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Joined: Jul 2019
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From: Dallas, TX
2016 Mercedes E250 Bluetec Designo
What is the scan gauge that's keeping tabs on the DPF? I've been very curious about any preventative maintenance and monitoring I can do on my 2016 E250 (which has had the AEM completed).
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Junior Member
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2014 E250
Go to Scangauge.com for more information. Scroll down to find Mercedes E250 2014 - 2016. I bought my scan gauge @ advance auto on line. I use the scan gauge to know when my DPF is regenerating. It is easy to setup. I have the Scan gauge ll. Mercedes could have installed a small gauge in the car to monitor the DPF, but for reasons I will never understand they didn’t.
I was at the Benz dealer a week or so back. I ask if the NOx sensors were failing @ about 35-40K miles. Service guy said yes especially with the new updated firmware they have to install. I have been emailing with Benzninja. He said he can recode so the NOx will last ten years minimum. The dealer charges about 1K per sensor. Fortunately I have not paid for one yet.
I was at the Benz dealer a week or so back. I ask if the NOx sensors were failing @ about 35-40K miles. Service guy said yes especially with the new updated firmware they have to install. I have been emailing with Benzninja. He said he can recode so the NOx will last ten years minimum. The dealer charges about 1K per sensor. Fortunately I have not paid for one yet.
Junior Member
Joined: Jul 2019
Posts: 60
Likes: 6
From: Dallas, TX
2016 Mercedes E250 Bluetec Designo
Other than monitoring, is there anything that we should be doing on these vehicles? I believe my car is about to fall out of the AEM covered warranty unfortunately. Just had both NOx sensors and tank heater replaced under the warranty a couple months ago - all clear/good right now.
Thread Starter
Junior Member
Joined: Jan 2019
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2014 E250
I am @ 132,000 miles - not sure what can be done to prevent future emission system problems. I am not worried about the DPF with the Scan gauge in place. I expect the sensors will be most of the problems. I plan to reach back out to benzninja. I do keep the engine air and fuel filter changed once a year or so.
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Joined: Jan 2009
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From: V E G A S
1922 Ford Model T / no OBD
My E250 is park right now, since I drive SUV in winter.
Nox sensors used to last long time, with occasional failures and I don't think they are subject to wear, but who knows.
I did check AEM scope and E250 BT did have new sensors installed with AEM. Manu fact, seems whole exhaust with DPF and SCR are new. When I was doing that, the SA told me it was $8000 job and MB mark DPF as rebuild unit, for discounted price.
I wonder what is current price for replacing Nox sensor. It was job going into 4-digits before AEM, as it require SCN coding, although you can buy probe only for less than $100 and easy swap it, leaving old module to avoid coding.
I still have 18 months of AEM warranty and I am happy about it.
E is my city car and DPF regenerates in city traffic just fine. Even if I abort DPF regeneration, it will resume next day once engine reaches 60C. Mind I live in hot climate. I used to drive with ScanGauge, but since now I have warranty, I moved gauge to SUV and don't worry about monitoring.
Newer MB diesels do have regeneration gauge on the dash, as well as DEF level gauge.
Nox sensors used to last long time, with occasional failures and I don't think they are subject to wear, but who knows.
I did check AEM scope and E250 BT did have new sensors installed with AEM. Manu fact, seems whole exhaust with DPF and SCR are new. When I was doing that, the SA told me it was $8000 job and MB mark DPF as rebuild unit, for discounted price.
I wonder what is current price for replacing Nox sensor. It was job going into 4-digits before AEM, as it require SCN coding, although you can buy probe only for less than $100 and easy swap it, leaving old module to avoid coding.
I still have 18 months of AEM warranty and I am happy about it.
E is my city car and DPF regenerates in city traffic just fine. Even if I abort DPF regeneration, it will resume next day once engine reaches 60C. Mind I live in hot climate. I used to drive with ScanGauge, but since now I have warranty, I moved gauge to SUV and don't worry about monitoring.
Newer MB diesels do have regeneration gauge on the dash, as well as DEF level gauge.
Last edited by kajtek1; Apr 11, 2025 at 12:33 PM.
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MBWorld Fanatic!
Joined: Jan 2009
Posts: 9,224
Likes: 1,797
From: V E G A S
1922 Ford Model T / no OBD
Mind Nox sensor is directly involved in engine efficiency, so any tampering with it has to end with lower performance.
Last edited by kajtek1; Apr 11, 2025 at 03:14 PM.
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