My 250 Bluetec has 2 identical NOx sensors and it took SD to determinate wchich one. Counted total 7 sensors on single pipe exhaust.
On those cars new sensor require SCN coding, what require subscription with Stuttgart.
Old thread http://www.benzworld.org/forums/w212-e-class/2765185-p229f-code.html

 

Thanks for that.

FFS REALLY!? SCN coding for a bloody sensor? I cleaned them both with brake clean and isoprop so will wait 40 cycles and see if it comes back.....

I have star diagnostics but obviously not connected to MB.... FUCK IT!!!!! Im still not sure which one it is. As the star diagnostics seemed to suggest one side then the other in the wording it was strange.

 

40 cycles?
My car computer gave me only 10 before it would turn the car into a brick.
In my case it was the sensor down behind the muffler, when the other was between DPF and muffler (from my memory)
Keep us informed how you succeed?

 

Just to update this I ended up getting a replacent nox sensor unit from ebay poland second hand. The car has been fine for the last two years.

This week im getting this fault code again..... Sigh.

What a POS. I aint paying $1400NZD for the sensor from MB so I guess I'll just have to go second hand again.

I cant believe this same bank same side same fault. The car has been fine other than this BS. How in the hell does a single exhaust sensor end up costing over a grand from a dealer? I mean the thing has decent fuel economy but its not light years ahead of my old w211 e55 on long trips really.

Anyway to clarify for those that do ever have this issue the petrol 350's DO NOT need scn coding to replace this part you just replace it.

The diesels as per the previous replies do need scn coding.

 

AFAIK Diesels SCN is needed if newer type sensor fitted (sensor come with electronic modules of their own, and if module is newer, SCN is needed).