how to fix P0420 code in Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on the electrical components.
• Allow the vehicle to cool down before starting work on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors (generally found on the exhaust manifold and after the catalytic converter).
  2. Remove the electrical connectors from both sensors.
  3. Use the O2 sensor socket to remove the sensors from the exhaust system.
  4. Install new oxygen sensors, ensuring they are tightened to the manufacturer's specifications (typically around 30 ft-lbs).
  5. Reconnect the electrical connectors to the sensors.

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

• Tools Required: Socket set, exhaust pipe cutter, gasket scraper.
• Sub-steps:
  1. Inspect the catalytic converter visually for any signs of damage or excessive carbon buildup.
  2. If replacement is necessary, use an exhaust pipe cutter to remove the old catalytic converter.
  3. Clean the exhaust flanges and install the new catalytic converter, ensuring that any gaskets are replaced as needed.
  4. Secure the new converter using the appropriate bolts and torque them to specifications (usually around 25 ft-lbs).
  5. Reconnect any exhaust hangers or brackets that were removed.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear any stored codes.
  3. Start the vehicle and let it idle for a few minutes.
  4. Take the vehicle for a test drive to ensure that the check engine light does not reappear and that performance is restored.