so, i promptly unscrewed my gas cap and re-screwed it in. tight.
i started the car again. light still on. went to bed. started the car again this morning. the light was still on. drove to the dealer. light was still on.
i told the dealer the light came on, and i had checked the gas cap, and it was nice and tight.
a couple hours later they called me back. i was right. sort of. the thing is, at some point, the gas cap had been loose, and the car’s computer noticed it. according to the dealer, i have to drive the car for at least 20 minutes 2-4 times for the car to believe the gas cap really is fixed.
$36 later, the sheet they gave me read:
HAS CODE PO440, GAS CAP WAS TIGHT, CAP PASSED WITH TESTER. EVAP VSV & CCV OPER. OK. PULLED EVAP SYSTEM INTO VACUMN, HOLDS VAC. DID CUST FIND GAS CAP LOOSE & TIGHTEN?
at lunch, a coworker informed me autozone lets you borrow a tester that reads the codes from the car’s computer and allows you to reset the systems as needed. hmmmph.
in a way, i was punished for attentiveness. had i procrastinated and waited a few days to go to the dealer, the light would have magically fixed itself.