From my own intimate knowledge on some of this you could have one or many -
1) The Coolant Sensor is defective, but still OK to drive, despite the error. (will actually turn into check engine light).
2) IGM in 2016's and some early 2017's were infact faulty - again, you can drive unless you get the Turtle
3) HV battery is defective, again in 2016's and early 2017's. (Early builds with delivery in January - March)
4) Following the most recent software update you will get a check engine light if you didn't get an update 2-3 weeks later with the fix. No idea of root cause.
All of this knowledge from the threads here and my own personal experience. The issues *are* identified and fixed, but very frustrating as the dealers are forced into an "Error = Fix" despite that other errors are very likely. Why they just don't offer some kind of preventative maintenance line item for these vehicles is unknown. That said, later 2017's and 2018's seem much less prone to these issue. Impossible, absolutely not, but coming from a manufacturing background somewhat - you got to use the parts you have before you can get the new "better" ones down the line.
