Nox Sensor issues (Freightliner DD13)

ok. I guess your second code was high doc inlet pressure. Do these.
a. Remove flex exhaust pipe between engine and 1-box. Check to see there is excessive soot on pipe wall. These must be little soot on walls. Start the engine and let it idle(coolant temp must be higher than 150f). Get helper and ask him to see how much black smoke is coming out from that pipe when you push the acceleration pedal quick. Football ball size of black smoke must come out and stop. If you see not a lot black smoke is coming out connect back that flex pipe.
b. remove dpfs and clean yourself by hot water. Youtube has videos. Or buy reman dpfs and install.
Nox sensor issue has no connection with this issue... Fix Nox sensor problem.

 

Just out of curiosity do you have APU on that truck?

 

Do you idle a lot?

 

b. a lot of black smoke
bad injector, cracked cac, leaking intake manifold, ...
there is no such a sensor

 

you are welcome.