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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before starting work.

2. Replace Faulty Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors on the exhaust system.
  2. Remove the electrical connectors from both sensors.
  3. Use the O2 sensor socket to unscrew the sensors from their respective locations.
  4. Install new oxygen sensors and torque to manufacturer specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connectors to the new sensors.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust hanger removal tool.
• Sub-steps:
  1. Raise the vehicle safely using a jack and secure it with jack stands.
  2. Remove any heat shields covering the catalytic converter.
  3. Disconnect the exhaust pipes from the catalytic converter using a socket set.
  4. Remove any exhaust hangers securing the catalytic converter.
  5. Carefully remove the old catalytic converter and install the new one, ensuring proper alignment.
  6. Reattach the exhaust pipes and torque to manufacturer specifications.
  7. Reinstall any heat shields.

4. Clear Codes and Test

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the ECU.
  3. Start the engine and let it idle for a few minutes.
  4. Take the vehicle for a test drive to ensure no codes reappear.