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

Solution

1. Preparation

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

2. Inspect and Replace Catalytic Converter

• Inspect the Cat:

  • Remove the heat shield if applicable using a socket set.
  • Check the catalytic converter for physical damage.

• Replace the Catalytic Converter:

  • If damaged, unbolt the catalytic converter from the exhaust system using a socket set.
  • Remove any exhaust hangers or brackets securing the catalytic converter.
  • Install the new catalytic converter, ensuring proper alignment.
  • Torque the bolts to the manufacturer's specifications (typically 25-35 ft-lbs).

3. Replace Oxygen Sensors (if necessary)

• Remove Old Sensors:

  • Use an oxygen sensor socket or wrench to unscrew the upstream and downstream oxygen sensors from the exhaust system.

• Install New Sensors:

  • Apply anti-seize compound to the threads of new oxygen sensors.
  • Screw in the new sensors and tighten them to the manufacturer's specifications (usually around 30-40 ft-lbs).

4. Clear Codes and Test

• Reconnect the battery.
• Use an OBD-II scanner to clear the P0420 code from the system.
• Start the engine and allow it to reach operating temperature.

5. Final Inspection

• Monitor the exhaust system for any leaks.
• Conduct a test drive for about 20-30 minutes to ensure no codes return and the vehicle operates normally.