I have a 2012 Western Star, did the same. Turned out to be the key switch, not loose wires but problem was inside the switch.
I'm sorry I ever got cascadia and a detroit motor . its been nothing but problems . jjjjuuuunnnnkkkk junk junk junk.
DD motors have always leaked oil at the H/P pump, Air compression, Oil cooler module, and Cam frame. That is still common on GHG17 motors. They can leak bad enough to cover the side of the motor and things behind it in oil. The H/P fuel lines.csn leak some and leak fuel everywhere. It will have a yellow golden look.
my truck started shut off on highways. after 1 hour of searching I have found the problematic area. Checked by DL and found SPN 520201 FMI 3 sitting inactive. Now I think the clock spring is worn and causing short. Sam Cab detects the short and shut off the truck. I will be in Amarillo area tomorrow. I will buy and replace the steering wheel's clock spring. Checked all wires near steering column and they look ok.
the clock spring was bad inside. I broke it to see inside. open wires were touching each other. replaced it and drove 3 hours .. no more shut offs.
I want my Freightliner Century back ! #### you california law makers ! Sick of fixing this junk ! tired !