Spn 3226 fmi 4&10 and spn 5246 fmi 0

There's also inactive 5031 fmi10.


Is this likely to be athe outlet nox sensor or wiring or is there something else I should be checking. It is in derate. Only other code active is 1569 fmi 31.

Replaced everything DPF, injectors, sensors etc 18 months ago.