P0420, what happens if you do nothing?

[HappyHooligan]

so earlier this year I got the P0420 code and replaced the back o2 sensor. Everything is great till about a month ago and it comes on again. I reset it, a few weeks later it comes on again, and I keep resetting the code. What happens if I don't do anything? Do I need to really replace it for the sake of the truck or just to pass smog?

 

[mtbtim]

I'd say you're probably fine driving it with this code, but if it's a case of your catalytic converter being partially clogged, your engine performance will suffer. I think the main thing is having to deal with getting it to pass smog. If I eliminated other possible causes, like replacing the O2 sensor and needed it to pass smog, I might try a product called Cataclean. https://amzn.to/38we1hd
It gets mixed reviews but some people have claimed it fixed their issue. So, before I'd drop big money on a catalytic converter replacement, I'd try the Cataclean and hope it worked to clear the CEL code.

I've gotten the P0420 code many times and it's always on a long road trip. Back at home, it never pops up.

This article discusses the possible causes of a P0420 code:
Toyota Parts | P0420 Diagnostic Code - Trouble Code Diagnosis Guide

This article discusses the side affects of having a clogged cat:
What Are The Bad Catalytic Converter Symptoms? | CAR FROM JAPAN

 

[Riceye]

Be very sure you have no exhaust leaks before the upstream sensor and the cat. Inspect the upstream sensor gasket very closely. Exhaust leaks in this vicinity will really screw up your upstream sensor's ability to dial in the stoic.

If that is good, Cataclean is a proven option. That, and more highway miles.

 

[19963.4lsr5]

To add to this, antifreeze going through the cat will also cause this code.

Are you watching your expansion tank level, or are you adding antifreeze every month or so?




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