how do I fix the P0420 code on my Honda Civic 10th Generation (2016-2021)?

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the vehicle's battery to avoid electrical issues.
• Allow the engine to cool before working on exhaust components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil.
• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Apply penetrating oil to the sensor threads if they are rusted or stuck.
  3. Disconnect the electrical connectors from both sensors.
  4. Remove the sensors using the O2 sensor socket.
  5. Install new oxygen sensors, tightening to the manufacturer’s specifications (usually around 30 ft-lbs).
  6. Reconnect electrical connectors.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter, new gaskets.
• Sub-steps:
  1. Raise the vehicle safely using jack stands.
  2. Remove any heat shields covering the catalytic converter.
  3. Cut the exhaust pipes near the catalytic converter if necessary using an exhaust pipe cutter.
  4. Unbolt and remove the old catalytic converter.
  5. Clean the exhaust flanges to ensure a proper seal for the new converter.
  6. Install the new catalytic converter with new gaskets, tightening bolts to manufacturer specs (typically 15-20 ft-lbs).
  7. Reattach heat shields and lower the vehicle.

4. Clear Error Codes

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the vehicle's battery.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Start the engine and allow it to reach operating temperature.