2013 KW T660 PACCAR CODE HELP

[DrPhixschitt]

I’ve seen very similar conditions before. On those, it was
A. A small leak at the bottom of the windshield got into the CECU.
B. Corrosion on the pins and sockets on the bulkhead connectors on the firewall.
C. Corrosion on the 5 amp,fuses to the CECU.
I hope this helps track it down. The leak scenario also affected the lighting, I.e. turn signals, low and high beam, etc.