I have had the first run of check engine light in almost 4 years with this truck and our mechanics have been unable to sort them out. Last week after me going to the workshop with 2 lights on but no effect on power or speed the guys screwed about and couldn’t fix it, they ordered a new heated line for DEF and sent me on my way, 2 days later the lights went out but they called me to ask me to go in and get the part fitted, on doing so I came away with both lights on and the empty DEF tank light of and derated to 55 mph, so off to Detroit diesel to get them to look at it, I spent most of the day there and now they say it needs anew DEF tank.
So now here I sit at home as the company loaned me the workshop pick up truck to drive home and back down there in the morning and hope it’s fixed.
hi pat had very similar problem with cascadia in the end it was a new harness
Had that problem new def pump that time.
Complete exhaust the next time
They fitted an entire tank and tank header complete with all the sender units. Everything is fine now.