Code p0420

2004 TOYOTA COROLLA

208,000 MILES • 1.8L • 4 CYL • 2WD • MANUAL

YAZIDAN

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The previous owner replaced the catalytic converter last year. What can cause a catalytic converter below threshold? i checked the voltage at idle of the post o2 sensor. It was lean and steady around 0.135 V.
Thank you

Feb 27, 2022 at 3:49 PM

SQM

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Hello,

The P0420 code can get triggered due to a bad oxygen sensor, catalytic converter or an exhaust leak.

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 trouble shooting guide for the code P0420 below. Take a look at this as it provides a lot of helpful tips on what to look for.

Please let me know if you have any questions.
Thank you.

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Feb 28, 2022 at 11:32 AM