I got some issues with the truck, I wanted to see if you might be able to help me give me some direction what it might fix my problem.
I have 2017 DD15, last month I got problem check engine came on. The def light started flushing and thr truck derated to 55 so I took it to the nearest dealer not far from home. They said first that the truck has code for nox conversion efficiency low and the outlet nox sensor is bad and need update on the modules, but after doing update and replacing the outlet nox sensor again same issue, no changes. Then they said they need to do valve adjustments because the air/fuel mixture is probably rich. They did that and then said again same issue. Next thing they changed the air filter and the air filter box thinking that might help but same thing. Then they said is probably a problem with the One box and the truck needs a new one. I towed back the truck from them and started working on it myself. First I took out all the def fluid and put new one inside and tested to make sure is good. Then I checked the Delta pressure sensor, maf sensor, air intake temperature sensor and HC doser they were never replaced and were all dirty with soot so I changed them with new. I checked the truck with dddl and did regen, the nox conversion is fluctuating, sometimes at the begining at 95-100% then goes down to 0 then around 20-60%. The Doc Inlet pressure is 0.4-0.6 Outlet Doc pressure half of that (around 0.2-0.3). Then I cleaned the DPF filters (2 dpf filters are new from last year) and cleaned the One box, installed them back (the place that cleaned it said the one box and dpf filters didn't looked bad/dirty/plugged at all), installed new inlet Nox sensor, new inlet Doc pressure sensor and hose (the hose was clogged), new soot sensor and did regen but it was same thing. I then installed new def doser but same thing. Tried Doc face plug still same. I had problem with the variable water pump leaking a little and since I see that the normal running temperature of the truck it goes from 205-220F (when the fan turns on at 320-221F), I thought it might be problem with the thermostat so I changed the pump and thermostat. Still same things. The temperature in the dpf goes to almost 1100F but nox efficiency still when starts sometimes is 97-100% and then just goes completely bad down to almost 0% or below 60%. The temperature still the same 205-220f on regen. It bothers me that sometimes it shows perfectly good nox efficiency and then goes bad. The harness from the ACM to the sensors looks good not damaged, checked the ohms were good from the ACM to nox outlet and were showing good. It's like when the truck gets hot the nox efficiency goes bad. The inlet nox is around 400ppm and outlet sometimes goes even more than inlet value. No Def crystalization.
What it could be the problem do you guys have some idea that can help me? I don't know anymore what to do. I am thinking what if the update on the modules caused the problem (because they got code for nox sensor, but did update and put new sensor)...or maybe the acm is not working properly...or maybe the harness is causing problems when gets hot ... I really am out of ideas.
Thank you very much