Originally Posted by wlindsey@gmail.com

Not sure if it’s helpful but almost every check engine light I’ve experienced has been fuel related - as in the quality of fuel you get varies widely even at the same service station. These engines (at least the P400) seem to be very sensitive. Usually it shows up as a warning about environmental sensor blah blah blah and resolves after a refueling at a quality gas station.

for me I see this issue most frequently when driving from Dallas to Colorado. I don’t know if it’s the random gas stations on the route, the octane change you get at altitude, or something else.