Hi,
A P0420 indicates the catalytic converter is operating below threshold. In most cases, the converter needs to be replaced.
What you could do is this. Using an infrared thermometer, check the catalytic converter intake temperature and compare it to the outlet temperature.
If the converter is working properly, the outlet will be hotter. Take a look through this link, it explains what I suggested in more detail and other things to check:
https://www.2carpros.com/articles/how-to-test-a-catalytic-converter
Let me know if this helps or if you have other questions. Note: If there is an oxygen sensor that is failing, there would be a code specific to the sensor.
Let me know.
Joe
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Friday, October 18th, 2024 AT 10:11 PM