I have a p0457 code - Evaporative emission control system leak detected, and was wondering when i replace the gas cap does it have to be vented? Reason for asking is because i have a non-vented one at home for some reason and if i can save money ill just use that but if it has to be vented then i must go shopping.

thanks for the help

 

Yes the cap must vent for smog. The smog mach. tests the cap for pressure and vacum. Im a smog tech at capitol Subaru.