Check engine light (every other tank)

2000 Corolla, AT, 105,000 miles. It seems as though I get a check engine light about every other time I fill up the tank. Part way into a tank of gas, the light will come on, and part way into the next tank the light goes out. It doesn't set a code, so when the light is out there is nothing to read. I haven't been able to get by my mechanic's place while the light is on. This started a few months ago when I was on a trip, and still continues. I tried changing the fuel cap, but still the same. I would guess O2 sensor, but hate to just throw money at it, so I'm driving my truck more, LOL. Anyone want to make a guess?

This is a common Corolla problem for that specific model.. tighten up the gas cap properly when you fill up, if you leave it lose it will keep giving you a check engine light, it keeps thinking that the cap is faulty if you leave it lose.

I had the similar problem. Tighten the cap till it clicks a few times and disconnect the battery for a hour or so and the problem goes away. For me anyway. Bingo

I bought a Fram cap a while ago to try to fix the problem. I understand Fram has problems with some of their products, so on Friday I'll try a Stant cap and see if it fixes the prob. Hate to give the dealer the money they want for that little stuff. I do always turn the cap for 6-8 clicks. Thanks for the responses.

buy OEM.. don't bother with cheap ones... specially if they're gonna be causing problems like this.

you might be able to just get a new O-ring for the fuel cap from toyota???

Resurrecting this old thread because the Check Engine Light came on again the other day. I pulled the code this morninig and it is 0420. I know the meaninig of the code, but it seems to me if the cat were bad, I'd also get an O2 sensor code also from the post cat sensor. Is there a more in depth meaning to the 0420 code on a 2000 Corolla? Thanks for any info.