2009 nissan rogue Sl , code P0420

What is your question?

My check engine light came on yesterday , I do need my air filter changed And I have the code P0420, what can I do to fix this matter

What makes this problem better or worse?

I dont know , other than , I put gas in it and my check engine light came on afterwards

How long has your 2009 Nissan Rogue had this problem?

1 day