Nov 2017, Altima had 18,173 miles, not one year old and the check engine light came on while drive it. Took it to dealer in san diego, diagnosis was a p0101 code (mass air flow sensor/orange pcv valve). Then at 20,598 miles, I saw my life flash before my eyes. I have 2012 Quest SL. About 120K miles on it. A warning light came up the other day. The code shows it is about mass air flow sensor. I decided to clean the sensor first. If that doesn't help, I would replace it. Anyway, I looked the location of the sensor under the hood. It's located the way back, almost under the dashboard and its facing inside..