NOx - Understanding How Many Of Us

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For the C-Class anyway, the warranty is a bit of a no brainer - costs about £700 for the first year but when you renew its £450 - bargain for a 9 year old car in the grand scheme of things, especially when one dealer visit will basically be that much if paying for it yourself
 
I'm another number in the stats, my 2017 S205 C200 has a faulty NOX sensor, I had the Big Motoring Warranty, but they only would cover the fix with an aftermarket cheap sensor, my mechanic (Merc Care) simply said he doesn't do the service with aftermarket. Still thinking what to do.
 
Hi, would push back. One of my cars was a 2015 with no service history.
 
My car has been diagnosed with this issue this week. 2018 plate C250 S205 with 38k miles on the clock.
Ive been told currently the NOx sensor on back order from Germany
 
My car has been diagnosed with this issue this week. 2018 plate C250 S205 with 38k miles on the clock.
Ive been told currently the NOx sensor on back order from Germany
Ever think of mapping them out I had glc with this problem at end of covid 4-5 mths wait on back order of parts mapped out , different car best it ever drove. Although a dealer got it done for me so was free. Would have no hesitation in doing it again if had same problem.
 
How long are these sensors supposed to last?
My car has only covered 37k miles!
When it gets replaced is there every chance it will need replacing again after such small mileage?
 
How long are these sensors supposed to last?
My car has only covered 37k miles!
When it gets replaced is there every chance it will need replacing again after such small mileage?
The sensor is only part of a chain, once replaced, the next link in the chain will fail soon after.
 
Sensor has now been replaced and fingers crossed will be ok for a while now!!
£451 all in.
Garage that did the work told me they are doing several a week! They have also had to replace the tanks on some newer E class merc's! Crazy!
 
All:

I have been trying to understand some logic to NOx sensor problems with my late 2014 CLS for over a year now. I have good garage and tooling facilities, Xentry, Vediamo and Monaco and vast amounts of literature and testing data. I have not finished my deep delving yet or read everything in these posts here, but, noting some of the queries posed, some short details of my conclusions so far might be of use and are thus:

  • Selective Catalytic Reduction (SCR) NOx systems were originally designed for big commercial diesel engines that run at relatively constant speeds for long periods. These systems are not really that suitable for people's stop/start cars and the Daimler/Mercedes engineers probably did the best they could to engineer a virtue signalling solution for those pushing it.

  • The original sensors fitted to the earlier BlueTEC vehicles did not have to work hard because the system never worked with cleaning NOx as a high priority.

  • The original sensors fitted to the earlier BlueTEC vehicles didn't like the Diesel Software Update, which improved NOx cleaning measures but caused them to generate faults/fail.

  • If you just replace one sensor or both with new ones they will also generate faults/fail relatively quickly.

  • Quick fix 'just wire in a new sensor probe' also looks to fail quickly or not work at all. Third-party sensor probes are lower quality than the original NGK NS11A probes, regardless of what people selling them tell you.

  • Mercedes NOx sensors are 'Smart' sensors comprising a Continental control unit and an NGK NS11A probe hard-wired together. Although the Mercedes part number is the same, the control unit can be calibrated differently by Continental and consequently there are likely to be incompatibilities between sensors with different calibrations. Both fitted should have the same calibration number and older ones may 'fail' quicker.
  • Most owners, garages and Mercedes dealers don't really understand the Daimler/Mercedes Selective Catalytic Reduction (SCR) NOx system at a very detailed level. It's therefore not surprising that there are many tales of woe with expensive new parts fitted and faults supposedly rectified, but appearing again. - I have been there myself.

  • The NOx sensors don't become operational until you have driven for at least 10 miles, and then they quickly go non-operational if idling.

  • A lot of the NOx sensor errors are generated after a couple of drive cycles. You therefore may not see any errors after a repair until the vehicle has completed at least a couple of long journeys. If all you do is e.g. commute 10 miles to work and back each day, it's unlikely they will ever become operational and generate a fault until you take a longer journey. - Just hope the ULEZ nutjobs don't cotton on to that!

  • It looks like Daimler/Mercedes are well aware of the fact that the Diesel Software Upgrade has caused the hardware problems, but are not publicising it. They have been made to remedy the situation in other countries by regulators, but not in the UK.

  • Apart from uninstalling the Diesel Software Update, which is problematic, the only long-term solution appears to be to have the 'additional installation of special equipment '30o '' service performed at a garage (or elsewhere) that has Xentry on-line services. This involves fitting two new NOx sensors and software updates to various ECUs, not just the Engine ECU, and then adaptions to parts of the exhaust system. This is the 'proper' Mercedes fix for NOx sensor problems, but they have not openly told people this.

  • Before code '30o', there was a code '121' , but I suspect that the software did not work properly and was therefore quickly superseded. Essentially, the software mod part that affects the NOx sensors is that it changes the speed of readings.

  • On a CLS 350 the original NOx sensors (both) number is A 000 905 34 03. The number once '30o' has been performed is A 000 905 35 06. The correct number is only reflected on Mercedes VeDoc and on-line elsewhere after '30o' has been performed. I believe it's the same for all other affected vehicles. The new sensors are the same price as the old ones and at over £1K for a pair it's important not to get the wrong ones ordered/fitted.

  • It's worth noting that later production date models (all models of vehicle) had the updated software and NOx sensors factory fitted. Consequently '30o' is not applicable to them. Any CLS where the EPC on-line part number for its VIN appears as A 000 905 35 06 has already been upgraded.

  • Many people will be unaware of the proper fix for a working system, although I am aware that there are posts elsewhere that have already said this, albeit with a bit less information as to why.

  • I am fairly certain that deleting or 'mapping out' the system is a solution, but illegal. Yes, not buying a BlueTEC as well or dumping it on another mug is another solution. This is about 'fixing' the problem, though.

  • Poor and misleading advice far exceeds the good stuff. Search the internet for 'additional installation of special equipment '30o '' and that should provide more authoritative sources of information - not many, but those that count are there.
Regards
 
So am I right in thinking that everyone in this thread who's successfully had the sensors replaced via goodwill / under warranty has got full Mercedes Service history?
 
So, the EML came on during a 200 mile trip on Friday.....
No secondary signs, performance remained good, mpg dropped, so I expected it to be a NOX sensor

And iCarsoft confirmed a 'stored' P229F Bank 1 Sensor 2 fault today

As per the question above, have 'we' had luck or rather goodwill from MB on replacing these or is it hand in pocket time?
If so, what's been the approach?
Its not seen a Main Dealer since it was 3 years old but seen by specialists since then (its a 2016)

Its already booked into MBS for its MOT, B Service and front pads (prob discs as well) in 2 weeks time, so I really don't need to add 50% onto the cost on to the bill for one or both of these if there is a route to goodwill......
 

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