CM2350 Fault Code 1683

[AlecLakeland413]

We have a 2015 prostar with intermittent derate. Code says high voltage signal to def heater valve. Valve works with direct 12v. Load tested the signal and return wires from J2 ECM plug to heater valve, both tested good. Has good heater fuse in aftertreatment fuse block. It recently also started running engine fan nonstop, the fan solenoid also test good with direct 12v. Wondering if anyone has ran into this problem caused from a different failed component. I went through the troubleshooting steps in site, including testing for continuity with any other wires in the J2 plug.