Honda Engine Error Code P0420: How to Fix It

Q: What causes Honda P0420 error code?

P0420 is typically caused by a faulty rear oxygen sensor that can't properly monitor catalytic converter efficiency, though it can also indicate actual catalytic converter failure, exhaust leaks, or engine misfires that damage the converter.

Q: Can I drive my Honda with P0420 code?

Yes, you can drive short distances with P0420, but prolonged driving may damage other emissions components and will likely cause your vehicle to fail emissions testing. Address the issue promptly to avoid more expensive repairs.

Q: How much does it cost to fix Honda P0420?

If it's just the rear oxygen sensor, repair costs range from $150-300. If the catalytic converter needs replacement, costs can range from $800-2000 depending on your Honda model and whether you use OEM or aftermarket parts.

Q: How do I know if it's the O2 sensor or catalytic converter?

Start by replacing the rear oxygen sensor first, as it's the most common cause and much cheaper. If the code returns after sensor replacement and proper test driving, then the catalytic converter likely needs replacement.

Q: Will Honda P0420 clear itself?

No, P0420 will not clear itself. The code must be manually cleared with an OBD2 scanner, and the underlying problem must be fixed or the code will return within a few drive cycles.

Abstract

Honda error code P0420 indicates that your catalytic converter's efficiency has dropped below the acceptable threshold. This is often caused by a faulty rear oxygen sensor that can't properly monitor the converter's performance, though it could also signal actual catalytic converter failure.