Hello - my check engine indicator recently turned on and read it might be due to a falty gas cap. Upon looking a the cap I noticed the flapper valve is not there any longer.

Can the missing flapper valve cause my check engine indicator to turn on?

Thanks!

 

There's so many different things that COULD cause the CEL, so the best thing for you to do is get the error code. The way to get the code depends on the year/model of your car.