VX - Check Engine Light during DFCO

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During a long highway trip, the check engine light came on in my VX twice. Both times, it was when I was on a long section of downhill, and was coasting in gear. I'm not sure exactly how long I was coasting, but it was at about the 1 mile mark both times (long sections of downhill in northern Oregon.)

Any ideas what would cause this? The light cleared immediately after restarting the car... no unusual symptoms. I was just wondering if this could be a sign of something *starting* to be a problem.

Mileage seems good, got in the high 40s on the trip (perhaps low for a VX, but I've had a pretty consistent average of 44mpg over the past 2 years.)