So I'm getting a code 90 check engine light. I always make sure to have the gas cap on tight after every gas fill up and even reset the ECU, but the CEL came back up again soon after.

 

They dont come on often for hondas. You can always look at the gas cap seal.

 

go pick up a new gas cap at a-zone or advance auto for 5-10 bucks.. cheap and if it doesnt fix it youre not out a whole lot

 

like he says....and if that doesnt help then you might have a evap system problem(like leaks)

 

accidentally left my cap at a station once where it was prepay and I wasn't used to that because at the time hardly any gas stations in my area did that. I didn't have any cards at the time so I just used cash. I called my mom at work the next day and had her run by the dealer to get it for me. I prob. drove with no cap for 2 hours or so and the cel never once lit up, I got back home that night and went to work the next day so I didn't get to put the new cap on till the next evening.