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Can we talk about the guy at the parts counter who said you can't fix a P0420 code without a new cat?

I was at the NAPA in Bellingham yesterday and overheard a young tech being told a P0420 on his 2008 Civic always means the catalytic converter is shot and needs a $900 replacement. In my experience, that's just lazy. I've cleared that exact code three times this year by fixing an exhaust leak before the O2 sensor or swapping a bad upstream sensor first. Has anyone else had luck with a specific diagnostic routine for P0420s before jumping to the cat?
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3 Comments
dylanwells
Man, my buddy's truck had that code and it was just a cheap O2 sensor.
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johnson.eva
Cheap sensors cause expensive problems.
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the_riley
the_riley6d ago
So what's your actual diagnostic order for checking everything else first?
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