ive got a 98 civic hatchback, and the past 2 times ive refuelled, the check
engine light has come on. the first time, i reset it by disconnecting the
battery, and that worked. this past time, the same technique wont work.

some more facts, which might help...

the gas cap is 2 years old, and aftermarket. lost the OEM one.

i make sure it clicks when i put it back on

yes, i *have* topped off the tank beyond one pump click, which leads me to
believe its something to do with the charcoal canister. bad habit i need to
stop doing, right?

i havent bought a code reader, or had autozone check for codes.

yes, i need to check for codes, but i figured others here have had the same
problem, so i figured id try here first. there is a sensor on the charcoal
canister, and i would guess that might be the problem. supposedly theres an
issue with the sensor, according to one website ive seen.