DEF system

[castillon11011]

So I’m getting a check engine light on, when I checked it code reads “ aftertreatment SCR catalyst conversion efficiency valid but below normal” it’s also telling me the Nox sensors are reading abnormal. Now I fell asleep all night with the truck idling and thought maybe I had plugged the filter so I did a forced regin and started to look at all the parameter, I found the both nox sensors were reading stable but the sensor for ammonia was reading not stable. Anyone have a clue about what can be going on here. I’m thinking maybe the def dosing valve could be plugged and not injecting enough def to cause a stable reaction but honestly I have no idea? Where’s the sensor that reads that information anyways? Any help will be appreciated