SPN 4364 FMI 31 Doser module.

https://www.justanswer.com/medium-a...x-engine-just-threw-code-fmi-31-spn-4364.html

He’s saying 5 mph derate 4 hours running time after light/code.

 

I’ve got a similar code on Pete 2017- also derate at 4 hours. My experience says it could be bad DEF, or clogged doser or def filter. An obstruction in the lines is possible. I am going to start with emptying def tank and replacing with some fresh fluid. Cheapest fix. What reset tool are you using?

 

###### emissions problems will be the death of you. If you've got the cash you might consider what I did. I was having emissions problems left and right so I had the filter replaced (not cleaned) and all the sensors changed while they had it off. Also the 7th injector. The only 2 sensors I didn't have replaced were the nox because I had already had one done a couple months earlier and the other was like $500. Anyways, since I shelled out the cash to have all that done I've gone well over a year now without any emissions related problems.
It's a lot up front but everything is so much more expensive on the road and why deal with the constant aggravation.

 

Ok sounds like a plan. Doser is often a culprit. I think my issue is that the def pump is either leaking or def lines to doser have crystallized or are leaking- so a blockage or not enough suction to get def fluid to doser. I have a different SPN number than you but still a derate situation