Code 1894 Now what?

[Moose]

(01-29-2020 )farmer70 Wrote:  So it can be inactive and everything will work ok? But if it is something really serious it will stay active?

That is correct. When it's active, it's just that, an active fault or problem with the system. If the problem is intermittent, a hiccup or a moment of bad communication on the truck's part you will have the MIL lamp intermittently turning on and off and instances of high inactive counts in the fault code history.

(01-29-2020 )farmer70 Wrote:  That code about the DEF unit was weird because it was full of DEF truck was bumped up to about 1100 rpm and out of nowhere the DEF light inside the DEF gauge comes on, the message center screen says DE RATE eminent. It was cold that night I wonder if it had something to do with that?

That you only have one count each of 3497 & 3559, I'd dismiss that as a momentary loss of B+ power to the aftertreatment system. (loose connection, bad relay, etc.) The 1894 could become an issue but as said above I'd start with the wiring and connections before condemning something way more expensive and should be checked anyway including the CECU inside the dash. The 4289 could be related as Paccar multiplexes the throttle signal through the CECU.