Got p0420 code on saturn ion two 2006 right after replacing bank one o2 sensor what Co ul it be now

Question

It's running great over nintymiles to 1.4th a tank just replace bank one o2 yesterday

1. List item

Answer 1

what octane fuel are you using? I suggest you use 91 octane fuel from shell and use a good fuel system cleaner.

low octane fuel will cause the catalytic converter to go bad faster. Sometimes the issue can be fixed if the catalytic converter is not bad already by using quailty fuel