[Kajtek1]

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

 

[Kajtek1]

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?