Any of literally more than two hundred problems.
http://www.tegger.com/hondafaq/error_codes.html#standard

First thing is to tighten the gas cap MORE than three clicks, then wait a
few days. If the light does NOT go off, read on...

Since you're in Canada, you can't just go to AutoZone and get the code read
for free.

Some ODB-II vehicles retained the old-style 2-pin service connector, which
can be jumped by a paper clip to make the MIL flash the error code. This
connector is usually blue or green and is located under the dash or behind
the passenger kick panel, or clipped to the underside of the glove
compartment.

If you find no such connector, you have no choice but to phone around to
see if you can get a discount rate on reading the code. Often garages will
refund the code-reading charge if you get the necessary corrective work
done there.

"roger" <monkeyracer@gmail.com> wrote in message:

Here is my guess:

P0401 Exhaust Gas Recirculation (EGR) Insufficient Flow

So, did I win?

Max