how to fix P0420 code on Honda Civic 11th Generation (2022-Present)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative terminal of the battery to prevent electrical issues.
• Allow the engine to cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil
• Use penetrating oil to loosen the upstream and downstream oxygen sensors.
• Disconnect the electrical connectors from both sensors.
• Remove the sensors using the O2 sensor socket.
• Install new oxygen sensors and torque to manufacturer specifications (typically around 30 lb-ft).
• Reconnect electrical connectors.

3. Inspect and Replace Catalytic Converter

• Tools Required: Wrench set, gasket scraper, torque wrench
• Remove the exhaust components leading to the catalytic converter (bolts and clamps).
• Inspect the catalytic converter for cracks or blockages.
• If replacement is necessary, remove the old catalytic converter and clean the mating surfaces of the exhaust pipes.
• Install the new catalytic converter with new gaskets, ensuring all bolts are torqued to specifications (check service manual for specific torque values).
• Reassemble the exhaust components.

4. Clear Error Codes

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0420 code.