scr warmup

[Mudflap77]

(05-10-2023 )JimT Wrote:  could check for a bad/faulty sensor or a damaged/broken wire for the temp sensors. It's possible there's an intermittent loss of signal. Also double check you ground connection/wires while your at it.

Not sure if any of those temps are calculated, but it does strike me odd that the DPF outlet temp is lower then the SCR inlet temp and the highest temp reading is from the SCR outlet? I'm not sure if it's even possible but, you didn't by any chance disconnect sensors/wires recently and somehow swap them around?

Also, have you inspected the {decomp tube} and can for DEF buildup or leaking? I don't know the design/layout of the exhaust on your truck but it's possible DEF could be building up and absorbing/deflecting heat from a sensor, if it actually is a sensor and not just a calculated value.

There's also the possibility that you have a blockage or leak in the DOC/DPF or exhaust system in general. That would throw the pressure readings off in turn messing up any values calculated from them.

The only other things I can think of is that either the turbo or EGR valve isn't functioning properly to keep the exhaust temps above the minimum threshold without kicking into warmup mode. But, then again, the entire point of warmup mode is to keep the temps up when the engine load isn't sufficient.

Anyway, I only have experience with my 2250 and it's long winding exhaust system underneath my truck. That was before it underwent corrective surgery, so the specifics of your system might be different from the mental model on which I'm basing my thoughts.

I graphed the temps while test driving no sharp changes on the graph.
The temps I posted are just when I happened to look at the screen. as far as the temp differences I'm guess it would be the same as when things are warming up DPF outlet would be hotter then SCR temp until they some what equalize. As exhaust temp goes down DPF would read cooler before the SCR. My main focus was that there wasn't a large difference between the reading.
The only exhaust related temp that is calculated as far as I can tell, is Exhaust gas temperature(calculated) during SCR warmup it runs around 750F after it gets out of SCR warmup it settles at about 350F.
I haven't had those temp sensor unplugged since they were replaced about 10 months ago, if memory serves they can't be swapped.
Decomp tube was checked out a couple of weeks ago and no buildup, exhaust was checked no leaks, and Vee clamps removed for checking the Decomp were checked and retightened twice since being removed(i've had them settle before).
DPF and DOC were new 14 months ago. Regens are typically 100 to 110 hour apart, current Ash load is 29.4%. I will get a pick of regen history here shortly as requested by Rawze.
I get the point of the SCR warmup but if 260F is above the warmup threshold 400F should be right?
Thanks for the reply