I replaced my Bank One catalytic converter recently. About one year prior I replaced all my O2 sensors. After installing the catalytic converter I drove the Traverse approximately 1 month and then the check engine light reappeared. It stayed on for 2-3 days and then went off. Drove the vehicles approximately 400 miles and then the light came back on. Code reader gave me the P0420 code for bank one catalytic converter. Questions ... Did the new converter go bad? Is there some other part / problem that is causing the code to reappear? Not sure where to go next. Any direction would be appreciated.