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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface.
• Disconnect the battery to avoid electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors (usually found before and after the catalytic converter).
  2. Unplug the electrical connectors from both sensors.
  3. Use an O2 sensor socket to unscrew and remove the sensors.
  4. Install new oxygen sensors, tightening them to the manufacturer's specified torque (typically around 30-40 Nm).
  5. Reconnect the electrical connectors.

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

• Sub-steps:
  1. Remove any heat shields or brackets securing the catalytic converter.
  2. Unbolt the catalytic converter from the exhaust system using a socket set.
  3. Inspect the old catalytic converter for signs of clogging or damage.
  4. Install the new catalytic converter, ensuring proper alignment and torque specifications (typically around 50-60 Nm).
  5. Reinstall any heat shields or brackets removed during the process.

4. Clear Error Codes and Test Drive

• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the system.
  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 reappear.