Please help solve my puzzle!

[Kenworth2012]

(08-02-2016 )Billdozer2 Wrote:  

(08-02-2016 )JMBT Wrote:  You are correct the inlet should be higher then the outlet, in the above post I just stated in backwards. During the regen mine were reversed, (inlet low, outlet high), then after the catalyst cooled back down to normal they switched back to normal or proper (inlet high, outlet low).

Mine does the same when doing a regen. The outlet will be higher than the input. I'm not really sure how that is possible, I guess science. Once the regen is over, the input will be higher than the output, like how it should be. The catalyst can still be hot and it will read "normal".

(08-02-2016 )JMBT Wrote:  Billdozer2, I don't know for sure where the NOX numbers should be, but at high idle I am around 150 on the in and 30 to 40 on the out...I would guess the lower on the out the better!! If you are at 389K and never changed one of the NOX sensors you are doing great!!

Yeah at low idle I am around 150 input and 50 or so output. During regens, it will be about 180 input and 190-200 output. Science. While driving, if I am coming up to a hill and giving the truck "the full monty", the input will go as high as 500 and the output will match that and then slowly go down to the 200's. I don't have any fault codes for the sensors themselves. Just the catalyst efficiency code. But it seems to be working ok. Or what I think is ok.

From what I have been reading, I guess I'm doing ok at 389k on original sensors. I may be replacing them soon after I figure out why my DPF is filling up too fast.

(08-02-2016 )JMBT Wrote:  I second Kenworth2012 on the DESA test, but be prepared it can run your motor at 1700 RPM for up to 10 mins while it is diagnosing. Not bad, just hard to listen to if you normally run your motor easy. I used to mine purring along at 1450.

I'll have to get on that DESA test. Someone else on here talked about that test a few months back. I'll have to do a search. 1700 rpms huh? I hit 2000 once. That was interesting. The cooling fan was on too because I had the a/c on. Almost sounded like the space shuttle taking off from on top of a scrap metal pile. I usually fart along at 1350 and 62-63 mph.

(08-02-2016 )JMBT Wrote:  By the way what kind of temps are you guys seeing during regen in the SCR? Just curious to see how they compare to mine.

I just finished doing a parked regen and my SCR temps were pretty close to the DPF temps. Near the end of the regen, the DPF was 970 input and 1100 output. The SCR was 1000 input and 970 output.

If the outlet is going higher than the inlet, then they are going bad and will cause the 3582 code. That's exactly what mine were doing. Now, it's just me but I changed both at same time as a set. I've had this problem before and would change one then about a month later the other would go out. And all my problems started around 360K. Absolutely nothing prior to that. You may want to check the flow rate of the DEF injector if both NOX sensors are reading about the same at all times. I had to change mine at around 380K. During the DESA NOX sensor test, mine never went above 275ppm inlet and 200 outlet at 1700 rpm. Remember the outlet should always be lower than the inlet due to the DEF being injected into the exhaust prior to the SCR catalyst and passes the outlet sensor on the way out the exhaust pipe.

My DPF inlet temp will reach 1250, outlet temp 1200. SCR inlet 1150, outlet 1100.

What is your DOC inlet temp? Mine will hit 750. If yours is low could be the fuel doser or injector is clogged up with soot. Again, check out Rawze's video on a forced regen and what to look for on youtube.