Nox Sensor Malfunction - Ad Blue Issue

[Ding009]

Good morning All,

Been a while since I posted, but hopeful you guys can help me resolve an issue, which I know has many posts already on here. (Mercedes CLS 220D 2015 Shooting Brake)

Apologies for repeating a post that has been done many times before, but hopefully mine is a little different as will pose some hypotheticals.

I currently have an amber engine light, which reports as Nox Sensor 2, Bank 1 Malfunction. Following this issue, I then started to get "Ad Blue - Engine Start not possible in 500 miles" which of course is counting down. Upon clearing the fault, it resets the Ad blue issue, and clears the engine light. This may last a day at best.

Currently I have made sure there is plenty of Ad Blue in the tank. And have also removed the Ad Blue injector under the car and cleared off the crystallisation from the injector and entry point on the exhaust. So happy that is clear.

This brings me to my questions. Due to the fault, I assume the Nox Sensor 2 is going to need replacing. Can this be done independently? Or do both Sensor 1 and 2 need changing together? I know main dealers suggest changing both, but is that necessary?

Second, and this is the part I am really hoping for help and experience. Once the sensor is changed (whether 1 or both), does the Mgmt System need to "relearn" the new sensor? And does this "Relearn" process need to be triggered by a good Mercedes Xentry style system, or is there something else that can be done around this? I was thinking something similar to take the battery terminals off? Or anything else? Will the car even start if I were to change the sensor in my garage and not trigger this relearn?

Finally (you'll be glad to read) is there a minimum requirement or type needed when buying a new Nox Sensor? Original research suggested this was a main dealer part only, but have since read this is not true. There seems to be quite a variance in price on these, so want to make sure I get something that will suffice and not just the cheapest.

Your help on this would be very much appreciated.

Thank you in advance

 

[malcolm E53 AMG]

Has the car been into MB for the emissions software update recently?

 

[Ding009]

Hi,
I know from the history that it went into Mercedes shortly before I bought the car. I bought the car in December 2019, and I know it went in at some point in 2018 under a recall for the software. Is this recent enough, or are you talking about a more current update?

Thanks

 

[malcolm E53 AMG]

Yes, it probably was the emissions update your car went in for you can always check with MB but as it’s five years ago there won’t be any liability on their part for the NOx problem you’re experiencing at the moment. You’ll need to check which updated sensors are suitable for your car there has been various upgrades over the last few years (due to so many failures) so I’d talk to a MB Independent about the problem they can check on STAR and as far as I know they need to be fitted in pairs

 

[DSK]

From memory of other threads, there is a parts number floating around also and the current nox sensors are version 3.

Changing one will only have you back to have the other one changed, so make life easier and do both at the same time.


Sent from my iPhone using Tapatalk

 

[dry run]

I had exactly the same on mine. Local indy said it needed 1 x Nox sensor and relevant software update.

I questioned this (as I'd read the threads on here about only changing 1 x sensor and updates causing trouble), but was told that this wasn't their experience.

So I had it done ( sensor was about £430 ) last September. I was convinced I would shortly get another sensor failure, but here we are 7- 8 months later and all is good.

 

[Wighty]

I had exactly the same on mine. Local indy said it needed 1 x Nox sensor and relevant software update.

I questioned this (as I'd read the threads on here about only changing 1 x sensor and updates causing trouble), but was told that this wasn't their experience.

So I had it done ( sensor was about £430 ) last September. I was convinced I would shortly get another sensor failure, but here we are 7- 8 months later and all is good.

Uh oh , you shouldn’t have said that out loud buddy, the car might hear you !

 

[Ding009]

Thank you all for the answers so far.

If anyone else has other experiences or details that could help me, it would be much appreciated