Check engine light keeps coming on (p0401).

check your gas cap if not tightened properly, it may cause check engine light to stay on. or if your gas cap is not that of your vehicle, it will also cause light to engage . you may have to have the comp reset.

I also replaced modulator, air intake boot, pcv and grommet and some vacuum lights. I just replaced the gas cap and saw that my gas cap was missing a large plastic cylinder piece from the inside. Cleared code p0401 from my 1998 toyota camry. And hasn't returned so far. But it's only been the morning so far. We will see.