Unfortunatly this is a somewhat common occurance on a lot of newer diesels i have driven. Each time it was in a new truck 2 Dmax and 1 Cummins at work, each time we hooked up a code reader and reset the code, the message never returned on the Dmax trucks and returned twice on the Cummins but hasn't returned since. I chalk it up to the Nox sensor parameters being so tight that the slightest reading over/under the window and the ECM thinks the DEF fluid must be faulty because emissions are not being scrubbed to meet EPA blah blah.
I have seen this discussion on many diesel sites and 99% of the time it is NOT bad fluid , but a faulty Nox sensor or glitch in emission system. Don't be surprised if the dealer points the finger at you for adding improper (non GM) fluid. Even though you have not needed to add any yet.
2016 Canyon CCLB 2.8L Duramax. SLT Nav/bose, driver alert,rear slider.