What does the check engine light mean on a 2002 Toyota Camry?
Most auto part stores will scan to determine problem for free
I recently had this happen on my 2000 Camry. It could be several things. Gas cap not on tight enough, make sure it clicks numerous times before closing the latch. Gas cap needs replacing or there is a pcv valve that can go out.
Trouble codes are numbered from 100 through 1780 and the "Check Engine Light" can reference any one of them. As mentioned above drive your car (assuming it's drivable) to a local auto supply store where they'll loan you an ODB II scanner. You plug it into the ODB port under your dash (to the right of the steering wheel post) and follow the instructions. You'll be shown the code and (usually) the actual fault. Again, as noted above the issue could be as simple as a loose gas cap or bad spark plug or as pricey as a clogged catalytic converter.
The scanner will also let you clear the code which is handy if the problem was a simple one.