Check engine light after refueling
 

I have a 1990 Mustang LX 5.0. Haven't had it long, just a couple of months. In that time, I've put maybe 500 miles on it. Today, I took it out to stretch the horses and fill up the tank. Well, like an idiot, I overfilled. When I started the car back up, the check engine light came on. Could this have come on just by overfilling the tank? I tried a reset and the light came back on. Seems to me I read somewhere that overfilling the tank can cause this warning light to come on. Also happens when the gas cap isn't tight.

I believe overfilling the tank can cause damage to the charcoal canister, or something like that.

Fuel backups into the vapor purge line and causes the charcoal canister to read no vacuum. This should reset itself after the fuel level drops and a few engine cycles pass.