2009 nissan altima p0420 code
First got the code threshold low bank 2. Replaced
the rear catalytic converter and downflow pipe.
About 3 months later got the code again threshold
low bank 1 replaced the 02 sensor and the front
catalytic converter. The catalytic converter was
definitely bad. Its been another 2 months and i
have the code again threshold low bank 1. Any
ideas? So frustrating.