how to fix P0420 code on Honda Accord Eleventh Generation (2023-present)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to ensure safety.
• Allow the exhaust system to cool before beginning work.

2. Replace Faulty Oxygen Sensors

1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Use an oxygen sensor socket to remove the faulty sensors.
3. Apply anti-seize compound to the threads of the new sensors.
4. Install the new oxygen sensors and torque them to the manufacturer's specifications (typically around 30 lb-ft).
5. Reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove any heat shields or components obstructing access to the catalytic converter.
2. Unbolt the catalytic converter from the exhaust system.
3. Inspect the converter for physical damage or clogging.
4. If replacement is required, install the new catalytic converter using new gaskets and bolts.
5. Torque the bolts to the manufacturer's specifications (usually around 40 lb-ft).
6. Reinstall any heat shields or components removed earlier.

4. Clear Codes and Test Drive

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
3. Take the vehicle for a test drive to ensure that the check engine light does not reappear and that performance is restored.