2006 Elantra 172 code

You don't have a K and N air filter do you? If so you have too much oil in it. Throw it away and clean the MAF sensor. If not , it still could be a dirty or bad MAF sensor. Or simple a vacuum hose leak. or maybe a dozen other things. What's your mileage? if not over 60K, take it back to the dealer (after you get rid of the K and N filter)

Actual milage is around 92,000. It turned out to be a plogged air filter. The input side of the box was full of cottony seed fluff and that seems to have filled up the air filter. I cleaned it out and changed the filter last night. Also reseated the MAF sensor cable. Put around 200 miles on it today and it seems OK.