I have this code. I have checked the live data with my reader and am trying to diagnose this to see if it could save me a catylitic converter. I just dont know what to look for in the live data. This shot was taken with engine warm at 2500 RPM. I also measured the inlet and outlet with a thermal temp gauge of the converter and temp seemed about the same. Diagnosing P0420 by Bryan Holloway posted Jun 23, 2016 at 10:48 AM
If you can monitor you downstream O2 sensor and see erratic readings or high voltage, you can confirm P0420.
So my upstream is "O2S B1 S1(V)" and its pretty constant around 3.3V as seen in the video, which is really high correct? I read its supposed to be below 1V. Does that indicate a bad sensor, or lean mixture or something? The downstream "O2S B1 S2(V)" seems to jump between .2-.4. But my reader isn't really "live" it just updates every few seconds.
3.3V is correct. That indicates an air/fuel ratio of 15 to 1 which is nominal. The first sensor is an air/fuel ratio sensor, not an oxygen sensor. You need to replace the catalytic converter.
