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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a level surface and set the parking brake.
• Disconnect the battery to prevent electrical shock.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Use the O2 sensor socket to carefully remove the faulty sensors.
  3. Install new oxygen sensors and torque to manufacturer's specifications (usually around 30 lb-ft).
  4. Reconnect the wiring harness to each sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed).
• Sub-steps:
  1. Use a socket set to remove the bolts securing the catalytic converter to the exhaust system.
  2. Carefully detach the catalytic converter from the exhaust pipe and exhaust manifold.
  3. Inspect the old catalytic converter for internal damage or blockages.
  4. Install the new catalytic converter, ensuring proper alignment.
  5. Torque the bolts to manufacturer's specifications (refer to repair manual for specific values).
  6. Reconnect any exhaust hangers or clamps.

4. Clear Codes and Test Drive

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