how to fix P0420 code on Honda Accord 10th Generation (2018-2022)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace O2 Sensors (if faulty)

1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) O2 sensors.
2. Disconnect the electrical connectors from both sensors.
3. Use an O2 sensor socket to remove the sensors from the exhaust manifold and catalytic converter.
4. Install the new O2 sensors, ensuring they are tightened to the manufacturer’s specifications (typically 30 lb-ft).
5. Reconnect the electrical connectors securely.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. If the catalytic converter shows signs of damage or if the O2 sensors were functioning correctly, proceed to replace the catalytic converter.
2. Remove any heat shields or brackets securing the catalytic converter.
3. Use a wrench to unbolt the catalytic converter from the exhaust manifold and exhaust pipe.
4. Install the new catalytic converter, ensuring proper alignment with the exhaust system.
5. Tighten all bolts to the manufacturer’s specifications (typically 30 lb-ft for flange bolts).
6. Reinstall any heat shields or brackets that were removed.

4. Clear Codes and Test

1. Reconnect the negative battery terminal.
2. Use an OBD-II scanner to clear the stored trouble codes.
3. Start the engine and allow it to reach operating temperature.
4. Take the vehicle for a test drive to ensure the check engine light does not reappear.