P0420 code

Good afternoon.

You need a real scan tool that can read the upstream and downstream O2 sensor readings.

In most cases, the cat converter is the issue. The way to verify it is to monitor the rear sensor. The voltage should be steady. If it varies like the front, then it is the catalytic converter.

https://www.2carpros.com/articles/catalytic-converter-replacement

Roy

O2s11 appears to be steady o2s12 appears to change after vehicle was still warm after a 10 minute shut off and was idling. After driving a few miles they both seem to stay unchanged. What does this tell you? Please see the video.

Please review and comment on this video. I was attempting to snap test the throttle while watching the oxygen sensors.

Snap test failed. the bank 2 sensor voltage went from 8 to 0.

You need a catalytic converter.

Roy

Do you recommend the Walker that you highlighted above? if I'm not having any drivability issues, what are the consequences of doing nothing? I don't have emissions testing here. Thanks for all your help. P.S. is this freeze frame information helpful?

It will not cause any issues except the check engine light yes you can drive it like this.

Roy

Can you explain what this info from scan tool means?

It means the rear O2 sensor is switching too much. When that happens, it will set the 420 code. The reading should be constant with very little variation in voltage.

Roy

Could that be due to the bad catalytic catalytic converter?

As I stated 3 times before, you need a catalytic converter.

Roy

I understand that. I was just wondering if the catalytic converter was causing that reading, or if it could be a combination of catalytic converter and bad downstream sensor.

The reading from the sensor is the indication that the catalytic converter has failed. It is not the sensor at all. It is doing its job by sending the reading.

Feel free to ask as many questions as you want.

Roy

Thank you!

You are welcome.

Always glad to help.

Roy