Toyota Corolla Check Engine Light – Catalytic Converter Problem?

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Toyota Corolla Check Engine Light – Catalytic Converter Problem?

Hi all,

My check engine light recently came on, and after scanning the codes, I got a P0420 error. From what I’ve read, this could mean an issue with the catalytic converter.

Has anyone else faced this problem? Could it be an O2 sensor instead, o r is the catalytic converter most likely bad? What are the repair options?

Lubaba asked on 30 Jan 2025 11:45:07 am

1 Answer

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Car Mechanic Expert - on 30 Jan 2025 11:49:53 am

The P0420 error code generally indicates that the catalytic converter is not performing as efficiently as it should, though it could also point to issues with the O2 sensors. In this case, the O2 sensors may be reading incorrectly, which could lead to a P0420 code even if the catalytic converter is still functioning.

To determine if the catalytic converter o r an O2 sensor is the issue:

If your O2 sensors are old o r have been in use for a long time, they could be providing inaccurate readings. Replacing the sensors might fix the issue.
If replacing the O2 sensors doesn’t clear the code, then the catalytic converter is likely to blame. A clogged o r damaged converter would need to be replaced.

Repair options typically include:

Replacing the O2 sensors: This is the cheaper and easier fix. If this resolves the issue, the problem was likely with the sensors.
Replacing the catalytic converter: If the converter itself is damaged o r clogged, this will be a more expensive repair, but it’s necessary for proper engine function.

Before proceeding, it’s important to have a mechanic inspect your car, as diagnosing and fixing the issue can be complex. They can run more specific tests, like checking the voltage and resistance of the O2 sensors, to pinpoint the problem.