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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the vehicle battery to ensure safety during repairs.
• Raise the vehicle and secure it on jack stands.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors on the exhaust manifold and catalytic converter.
  2. Unplug the electrical connectors from both sensors.
  3. Use an oxygen sensor socket to remove the sensors from the exhaust system.
  4. Install the new oxygen sensors and torque them to the manufacturer's specifications (typically around 30-40 lb-ft).
  5. Reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter

• Sub-steps:
  1. Remove any exhaust hangers or clamps securing the catalytic converter.
  2. Disconnect the exhaust pipes connected to the catalytic converter.
  3. Remove the catalytic converter from the exhaust system.
  4. Install the new catalytic converter, ensuring a proper fit.
  5. Reattach the exhaust pipes and secure them with clamps and hangers.
  6. Torque all connections to the manufacturer's specifications.

4. Final Checks

• Sub-steps:
  1. Reconnect the vehicle battery.
  2. Clear the P0420 code using the OBD-II scanner.
  3. Start the engine and let it warm up to operating temperature.
  4. Monitor the oxygen sensors' voltage output to ensure they are functioning correctly.