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Challenging situation with the upstream Nox sensor.


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I own a 2017 Eclass 220d that has been driven for a total of 75000 kilometres. I hail from Wolverhampton, located on the Birmingham side. A few weeks ago, I experienced the illumination of the engine management light in my vehicle. I promptly sought the services of an independent Mercedes expert located in Birmingham. The garage informed me that there is a malfunction with the upstream NOx sensor and it has to be replaced. The garage replaced the nox sensor with a genuine Mercedes part and cost me a total of £800. However, the EML (Engine Malfunction Light) reappeared after driving for a distance of 70 miles. Returned it to the same garage. The garage informed me that there was a new software update, so they proceeded to upgrade the software. However, the same problem with the upstream NOx sensor reoccurred. Upon reevaluation, the garage informed me that they would schedule an appointment for me at a Mercedes garage. I specifically requested them to inspect the sensor, since it is a recently installed component. After a period of two weeks, the Mercedes garage was unable to schedule an appointment for me, consistently providing excuses. Eventually, the garage contacted me and informed me that Mercedes had instructed them to do a fresh software update. As a result, I returned my vehicle to the same garage. The software was upgraded by the garage. Once again, the upstream NOx sensor failure light has reappeared, indicating a streak of unfortunate luck. Currently, I am uncertain about the course of action I should take. Is anybody experiencing the same problem? I had been contemplating scheduling an appointment independently with my nearby Mercedes facility; however, they are imposing a fee of £178 only for diagnostic services. However, I am already aware of the error code. Will I be billed £178 just for the purpose of establishing a connection with the equipment, or may I provide them with the trouble code beforehand? Therefore, they may simply inspect the upstream sensor and wiring. This is my first Mercedes, and it is a diesel vehicle, therefore my knowledge of it is limited. Fault code: (P300651--The Nox sensor 1, located in cylinder bank 1, is experiencing a problem.
Thank you.

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In order for the Mercedes dealership to take any action, you must pay them for their investigation charge, even though they will likely reach the same conclusion that you have already reached. However, when the defect is documented in their system, they may input the information into the MB UK computer system to see whether it can be fixed with a significant payment from MB as a gesture of goodwill.

There is a substantial probability that "the computer says no". Subsequently, you have the option to personally reach out to MB UK, if desired, along with the physical defect report obtained from the dealership. You can then articulate that you have come across several accounts of NOx sensors being changed at no cost due to their acknowledged problematic nature. Based on the service history of your automobile, it is probable that they will provide either full or partial payment.

When my vehicle became 7 years old, I had the sensors changed. MB UK provided a contribution of £1100 towards the cost. However, this occurred after they had been substituted with a new focus at around 18 months and almost 4 years of age.

Within a span of less than three years, the same problem code resurfaced once again. I opted to avoid the inconvenience and purchased an inexpensive code reader to nullify the code. It was mentioned a few times in the following months, but eventually stopped attempting to grab my attention. Approximately one year later, I had the same procedure. One significant distinction for me is that my automobile runs on fuel, which means it relies less on receiving accurate information from the sensors. It may not be feasible to 'convince' the ECU to cease its persistent reminders. Additionally, it is unlikely that it will emit significant amounts of NOx.

Best wishes.

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I had already sent an electronic message to this address one month ago, elucidating the circumstances, but, I have not yet gotten a response. A member of the Mercedes Facebook group advised me to follow a certain course of action, but he neglected to provide me with the email address due to his forgetfulness. Consequently, I resorted to doing an online search and subsequently sent the email. I anticipate receiving a response to my inquiry.

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I have been experiencing the Nox sensor problem for a considerable period of time with my 2015 E-Class cabriolet. The issue began when I brought my vehicle in for the airbag recall and explicitly declined the software update. After a few days, the dashboard warning light illuminates. I connect a diagnostic tool to the vehicle and it indicates a fault with the NOx sensor in bank 1. I am able to reset the error code a few times, but eventually it remains permanently on. I have been driving for many months without any impact on the car's performance. After doing extensive study, I had planned to undertake the task of modifying it myself or, at the very least, cleaning it beforehand. It did not seem too difficult, but I would need to acquire the necessary coding skills. Regardless, I decided to give MB a try. It wouldn't hurt to attempt to get a new nox sensor via persuasion. To my astonishment, they agreed and are replacing both free of charge! What on earth! I did not need to implore, beseech, or negotiate! The only requirement was that I had to do a software "upgrade," which would inform the technician if the nox sensors needed replacement or not. I find it amusing that I engaged in a conversation where I expressed my thoughts honestly. However, it is unacceptable to have vehicles equipped with fraudulent software. When my car was taken for the airbag recall, it is likely that some software was installed, resulting in the nitrogen oxide (NOx) fault. Consequently, I am compelled to return to Mercedes to have the software updated, which, according to the technician, improves fuel efficiency and the dosage of AdBlue. Regardless, he just grinned in response to my candid discussion about conspiracies. I received information over the phone that the downstream NOx sensor in my car was subject to a recall. However, it required a software update. I was compelled to comply with this requirement and had no alternative. Interestingly, there is a significant delay of 4 to 6 weeks in obtaining the sensors, which means my vehicle will be out of service for a few weeks, coinciding with the expiration of my MOT.
The car in question is an MB a207 from the year 2015. There is no recorded history of the vehicle at MB, but it was bought from MB Wolverhampton in 2018. Approximately 4 months ago, a warning light for the NOx sensor on bank 1 appeared. However, this did not have any impact on the vehicle's performance, and all other aspects, including the adblue system, were functioning normally.
Contacted MB Wolverhampton, who would install free of charge after doing a software update.

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Multiple codes exist for NOx sensors. After undergoing two sensor replacements by MB, the first time being fully covered and the second time with a £1k payment, I became frustrated with the inconvenience and opted to have the code erased. After a few years, a different code emerged. I erased it using my On-Board Diagnostics (OBD) reader, but it reappeared after a month. After persisting in this behaviour for many months, it ceased to bother me. After a period of 18 months, a sense of déjà vu occurred. That occurred more than a year ago and there have been no such occurrences since then. (By the way, this information pertains to the M276 V6 petrol engine.)

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Fortunately, they replaced it free of charge. My issue has been resolved. The sensor was changed once again by an independent garage, and now it is functioning properly.
Were you required to remunerate MB for the diagnostic price in order for them to examine the sensor?

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