2014 MDX "Emission System Problem"
 

In case anyone else runs into this issue: my wife was driving along on the highway when she says the dash says "emission system problem" with the Check Engine light. She also says it feels like it has no power and is having a hard time maintaining speed. Shop ended up replacing an oil valve (rear cylinder head spool valve, I believe) that had apparently failed. Naturally I was at 77,000 miles (7,000) past the powertrain warranty.

Another very odd issue popped up at the same time, along with the check engine, there was a blind spot system issue. The shop did some troubleshooting and didn't have a fix, honda/acura engineering suggested a re-calibration of the Blind spot system but it was raining so shop said the calibration won't work with rainy conditions. I decided to take the car home and have them fix the blind spot issue later. On my way home (it's still raining) the rear wiper is not working. Apparently there is a fuse that provides power to the rear wiper as well as a part in the blind spot system. It ended up being Fuse D10 (front footwell, driver's side). Maybe that will help someone facing a similar electrical gremlin.