[colterHD]

very common problem with the detroits, often in stationary burn with pass efficiency test just fine.

check urea content in the DEF (is always good but never hurts) should be about 29-31 %
no leak anywhere im sure youve checked
DEF doser quantity test (should be about 130ml) but its new so im sure its okay
scope the one box while the def doser is out, checking for crystallized def buildup, 
you can force a burn and monitor or log your nox conversion + input output values, ADS pump speed and DEF pressure as well as pump demand in g/h, depending on how the graph develops you can check for nox sensor drift.

has it had the RS service kit done recently?
new DEF pump recently?
do you have the manual or the troubleshooting procedure in your DDDL as it should be a permanent code

if you dont have already you should get a DEF quality code as well as soon as you fill the DEF tank up again if this code remains active

**added to expand on previous thoughts for anyone with this issue in the future**

that code i almost always related to DEF and DEF pump issues, a NOX sensor drift is very unlikely as you said they're both new,

these are roughly the steps id take

dealership can give or sell you a test strip for the DEF (they do expire) you siphon some DEF out and run it over the test strip, it should bead off, if anything absorbs into the strip your DEF is contaminated.

if you have a refractometer you can see what urea content it has as i stated

any external leaks or kinked lines is an issue

you can perform the ADS self check, pump speed test, leak test to go into the integrity of the DEF system further, pump speed should be 1200-1500 to maintain 125-145psi.

you can remove the DEF injector and check the quantity, if its under target you can clean the injector with warm water, if its over it'll need replacing but its new so it should be fine, while its out if you scope the one box with a bore scope some white trails are normal but large quantities of crystallized DEF indicated its not mixing properly causing your nox conversion to fall below the 70% limit. there is a procedure in DDDL that involves unplugging the injector and running a regen to burn the buildup off, this doesn't fix the cause

when monitoring or logging data during a burn i watch the nox values and conversion, conversion will jump once nox sensors are online, there should/could be a outlet nox jump as it starts dosing as well, this is normal but depending on the time and graph movement could be that DEF burning off but at this point you should have checked with the scope,
watching ADS pump speed its should stay around the 1400rpm point, our pressure should stay consistent as well, the demanded vs actually g/h of def you want to watch if it start wanting 800g/h or more which is might start asking for ridiculous amounts when the conversion % drops

the most popular cause of this code is the pump, the DEF filters are rarely changed regularly and they degrade, youll have pieces of filter going through the system and plugging up screens + check valves + and regulator, the filter (canadian $) is about 280-300, the RS service kit is around $600 or twice as much, youll need to drain coolant and remove DEF pump, it has filter and screen plus regulator in the pump as well as the screen and two checks in the injector, performing this service and cleaning all lines and components usually does the trick, sometimes however after doing this kit the pump will fail (usually overspeed to maintain pressure) and you spend $800 on a pump with brand new items in it,


i would recommend the service kit or cleaning the injector and replacing the pump, but definitely make sure you have no DEF buildup as a effect of whatever is causing the issue,

this is one of my most hated issues to chase on the detroit's and i cant say ill be for sure correct but its the right direction and its been the main issue and fix in the last two years for me