CM2250 FAULT CODE

[doarmihai]

Did anybody had that fault scr catalyst conversion efficiency below normal operating level moderately severe ....to a different level?
Cummins engenier suggested me to switch nox sensor betwen each other
I am tracing the firs occurrence at 650 000 miles. Once i got over 700 000 it started to ask me for regen. In conclusion it seams that this code will trigger dpf alarms...fake alarms at about 800 miles interval . The engine mpg stays above 7 till dpf alarms comes one. Say I'll reset ecm...it goes 800 more miles till next alarm. One time i notice that fault went away after replacing def filter. Other times went away if drove I10 colidor. I will post any good inputs if i will discover any. If not surgery has to be scheduled