It has come on before and then gone away for months. I was just wondering why this would happen? Possible bad O2 sensor? The car drives normal when the light doescomes on, no black smoke no gray bluish smoke nothing out of the ordinary except the check enginelight is on.

 

without a code you could change HUNDREDS of things before its fixed

 

I know that with my 01 that if I do not put the gas cap on properly (let it click at least 3 times) I will get a check engine light. Once I put the cap on "tight" the light will turn off after a few restarts.

 

Figured it out, wasnt the gas cap. Cleared the codes and it made the check engine light go off. Something about voltages.