oxygen sensor simulator

My cel came on.(p0137 I changed the secondary o2 sensor and the cel persisted after resetting the ecu. I installed an o2 simulator to help me diagnose and the cel came on after a week, giving me a p0420 (bac cat).

Does this mean I have a wiring problem somewhere between the ecu and the sensor? Any help will be greatly appreciated, thank you.

if you installed the sensor make sure the wires from the sensor are unkinked or twisted because if they are it could sometimes give the same code .but cats failing on civics are not unheard of if it's under 80k it still maybe covered under warranty.