I need help with getting that PO420 code. I've replaced the gas cap which worked for a year - now I have the code back. It seems related to filling with gas as the light will go off and then when I fill with gas again it comes back. 118,000 miles 2002 camry - should I spend the money and just replace the sensor or what? I did add some injector cleaner and that made the code go away - but when I filled with gas after that - it came back. Help!