how to fix P0420 catalyst efficiency code in Honda Civic 11th Generation (2022-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the vehicle is on a level surface and secure it with wheel chocks.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors (usually near the exhaust manifold and after the catalytic converter).
  2. Unplug the electrical connectors from both sensors.
  3. Use an oxygen sensor socket to remove the sensors from the exhaust pipes.
  4. Install new oxygen sensors, ensuring they are torqued to the manufacturer's specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connectors.

3. Inspect and Replace the Catalytic Converter

• Sub-steps:
  1. Visually inspect the catalytic converter for any physical damage or signs of overheating.
  2. If necessary, remove the catalytic converter from the exhaust system. This may involve removing bolts or clamps.
  3. Clean the exhaust flange surfaces to ensure a proper seal when installing the new converter.
  4. Install the new catalytic converter, ensuring it is properly aligned and secured with the correct torque specifications (typically around 25 lb-ft).
  5. Reconnect any exhaust hangers or heat shields that were removed.

4. Clear Codes and Test

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the stored trouble codes.
  3. Start the engine and allow it to reach operating temperature.
  4. Perform a test drive to ensure the vehicle operates normally and the check engine light does not reappear.