Based on the comments below - I wonder a polluted highway/slow traffic can trigger it - see below.
Note: Believe it happened many years ago - say 5 on my 2000 Acura Integra. Not sure what the code was but it was reset by the m/c - now it on a slow freeway - I recall there was a truck in front of me smelled bad - so I changed vent to circulation - wonder that pollution might have triggered it in my car. I recently did complete timing belt:
" The most “common cause” of the “check engine” light is the Exhaust Gas Recirculation
(E.G.R.) valve on most Asian vehicles. Although
it is sometimes quite disconcerting to have the
light come on it is usually not harmful to the engine or it’s performance. The E.G.R. valve is
exposed to high temperatures and it can get
“carbon fouled” easily and therefore send a
signal to the Electronic Control Module (E.C.M.)
that there may be a problem (not necessarily
a significant one)."