P0134 and p0420 codes new 02 sensor and new exhaust.

Question

I have had these codes come up I replaced the exhaust and 02 sensor. Still comes up

Answer 1

P0134 - 02 sensor circuit , no activity detected

This is the heater circuit for the 02 sensor, when there is no power going to the 02 heater circuit , This is a slim solution but it does occur and  resolve P0134, The heater circuit is the blue/red wire. It shared with sensor 2 which is the downstream 02 sensor. A shorted downstream 02 sensor would cause a P0134 and not even set a code for the downstream 02 sensor. You may just have to replace the downstream 02 sensor