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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shocks.
• Allow the engine to cool if it has been running.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream (pre-catalytic converter) oxygen sensor using an O2 sensor socket.
2. Install the new oxygen sensor and torque it to the manufacturer’s specifications (typically around 30 lb-ft).
3. Repeat the process for the downstream (post-catalytic converter) oxygen sensor if it is faulty.

3. Inspect Catalytic Converter

1. Visually check for any dents, holes, or rust on the catalytic converter.
2. If damaged, remove the catalytic converter by unbolting the flanges or clamps securing it to the exhaust system.
3. Install a new catalytic converter, ensuring all gaskets are replaced and the connections are secure.

4. Check Exhaust System

1. Inspect all exhaust pipes and joints for leaks. Use exhaust leak detection fluid to check for escaping gases.
2. Repair or replace any damaged sections of the exhaust system.

5. Clear Codes and Test

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the P0420 error code.
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 return.