1998 Toyota Corolla Q&A

1998 Toyota Corolla Question: I have a p0420 code where should I start

Before that I have a code that the auto zone guy said it was a oxygen secer I never replaced and just reset now it says p0420 bad cat. I runs great should start by cleaning maf or what lol -
Answer 1
Start by having a SHOP verify sensor and converter function with live data scan. -