could not tightening gas cap cause p0421 & p00446 come on in a Hyundai sonata

Question

Could thes two codes be showing because the gas cap wasn't clicked closed after pumping gas ? And if so is the only way to make he light go off is to clear the codes off

Answer 1

P0421 Warm up catalytist efficiency below threshold

P0446 Evaporative emission control system purge control valve circuit malfunction

No more than likely this would be set due to a loose fuel cap, What you would set is a large evap leak, . The purge valve can set a P0421, what happens when P0446 set it leans out the fuel trim which does not have to set a lean fuel trim code, .