Cascadia DD15 SCR system not working

Hi,
I'm working on DD15 with active code for DEF quality low.
Almost everything is replaced - Def dosser unit, air valve, both NOX sensors.
I tested the def dosing and quantity is OK.
During regeneration temperatures are in the limits and the NOX sensors as showing about 240-250 inlet and 240-280 outlet..

Do you guys have any idea what else I need to check to find the problem?

Hi,
I'm working on DD15 with active code for DEF quality low.
Almost everything is replaced - Def dosser unit, air valve, both NOX sensors.
I tested the def dosing and quantity is OK.
During regeneration temperatures are in the limits and the NOX sensors as showing about 240-250 inlet and 240-280 outlet..

Do you guys have any idea what else I need to check to find the problem?

get new def fluid, and try this additive that for fuel. Helps clean dpf filter and injectors.

Hi,
I'm working on DD15 with active code for DEF quality low.
Almost everything is replaced - Def dosser unit, air valve, both NOX sensors.
I tested the def dosing and quantity is OK.
During regeneration temperatures are in the limits and the NOX sensors as showing about 240-250 inlet and 240-280 outlet..

Do you guys have any idea what else I need to check to find the problem?

Check your fuel system and oil consumption

I also put new DEF fluid. Still the same situation.
The strange thing is that NOX outlet sensor has higher values than the inlet.

I also put new DEF fluid. Still the same situation.
The strange thing is that NOX outlet sensor has higher values than the inlet.

What year are we talking here? epa 07 epa 10. You mentioned air valve so i am thinking older system. Unplug the def doser injector by the def air valve assembly and run a forced regen through the system. (If possible run a DOC face cleaning routine). Sounds like the scr system is bricked full of def Crystals. Just a Idea that has worked for me before.

I also put new DEF fluid. Still the same situation.
The strange thing is that NOX outlet sensor has higher values than the inlet.

What year are we talking here? epa 07 epa 10. You mentioned air valve so i am thinking older system. Unplug the def doser injector by the def air valve assembly and run a forced regen through the system. (If possible run a DOC face cleaning routine). Sounds like the scr system is bricked full of def Crystals. Just a Idea that has worked for me before.

Cameron is correct. Has worked for me also. I also have had bad outlet nox sensor. Replaced it. Same problem. Nox sensor was bad right off shelf. Those 2 days sucked!

If the outlet NOX is higher than inlet, 90 percent of the time, the SCR AKA (1 box) is the culprit. Only if you know the NOX sensors are good

WHEN THE NOX OUTPUT SENSOR HAS A HIGHER READING THAN THE NOX SENSOR INPUTS THERE IS AN INTERNAL PROBLEM WITH THE SCR BOX SOMETIMES THE PROBLEM IS NOTHING ELSE REPLACING THE TWO FILTERS CALLED DPF OTHERWISE YOU WILL HAVE TO REPLACE YOUR COMPLETE SCR BOX.
NOX LIMITES
INLET 270
OULET 90
CONVERSATION NOX 0.085

I've ran a 2013 DDEC13 on a dyno and found that the SCR catalyst was worn out- was running 45%(400NOxin/230NOxOut) efficient- only had 450,000 miles on it- had to get a new 1box.