Throwing code P0420

2001 CHEVROLET IMPALA

135,000 MILES • 3.8L • V6 • 2WD • AUTOMATIC

HEYMAN0718

MEMBER
1 POST

My car listed above LS model, is throwing code P0420, haven't noticed anything acting different. I'm just curious as to how I could fix the code and get the warning light off my dash.

Apr 18, 2022 at 11:50 PM

SQM

✓Experienced Mechanic
6,383 POSTS

Hello,

The code P0420: Catalytic efficiency below threshold, bank 1.

This could be due to a faulty oxygen sensor or bad catalytic converter.
This is emission related and for the most part does not impact drivability.
However, this will cause the vehicle to fail emission testing.

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor
https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

I have attached the diagnostics steps below for your reference.

Let me know of any questions.
Thank you.

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