Hi:
In most cases, a P0420 does indicate the converter is operating below threshold and needs to be replaced. There are different products that are available that are designed to clean and regenerate them, but they don't always work. From experience, Lucas has come out with a new product, and I have seen the best luck with it, but the directions need to be followed exactly.
As far as what you are dealing with, there are ways to determine if the converter is actually at fault. By using an infrared thermometer, you can check converter temps to determine if it is working. The temp should be hotter at the outlet.
Here is a link that explains how to check it. Take a look at this link and try it. If you have questions, please let us know.
https://www.2carpros.com/articles/how-to-test-a-catalytic-converter
Let me know if this helps.
Take care,
Joe
Thursday, January 8th, 2026 AT 7:52 PM
