Code P0420?

TWEBB101

MEMBER
2008 HONDA ACCORD
2.4L
4 CYL
2WD
AUTOMATIC
203,000 MILES

A couple of days ago my check engine light came on. Plugged a scanner in and got P0420, but that was it, no other info. Google says catalytic converter or O2 sensor. Can you help?

Friday, October 18th, 2024 AT 9:52 PM

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,772 POSTS

Hi,

A P0420 indicates the catalytic converter is operating below threshold. In most cases, the converter needs to be replaced.

What you could do is this. Using an infrared thermometer, check the catalytic converter intake temperature and compare it to the outlet temperature.

If the converter is working properly, the outlet will be hotter. Take a look through this link, it explains what I suggested in more detail and other things to check:

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

Let me know if this helps or if you have other questions. Note: If there is an oxygen sensor that is failing, there would be a code specific to the sensor.

Let me know.

Joe

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Friday, October 18th, 2024 AT 10:11 PM

TWEBB101

MEMBER
178 POSTS

Thanks Joe. I ordered a temp gun and then the check engine light went away. :) I'll watch it and see what happens.

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Wednesday, October 23rd, 2024 AT 6:51 AM

JACOBANDNICKOLAS

MECHANIC
109,772 POSTS

Thanks for the update. It sounds like you have the same luck as I do. LOL

Regardless, let me know if things change or if I can help in any way.

Take care,

JOe

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Wednesday, October 23rd, 2024 AT 7:22 PM