Thread: p0420 code, which o2 sensor do i replace?

Originally Posted by copgtp

I might live under a rock, but can you explain this for me?

This is useful if you have a hi flow cat that sets off the engine light and dont have a custom tune that deletes the code. It's just a peice you screw on to the end of the 02 sensor and then screw it in the pipe. It pulls the sensor back out farther so it detects less and tricks the sensor.