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

Solution

1. Preparation

• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Gather tools and parts required for the repair.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors (usually found in the exhaust manifold and just after the catalytic converter).
  2. Remove the electrical connector from each oxygen sensor.
  3. Use the O2 sensor socket to unscrew the sensors from their respective locations.
  4. Install new oxygen sensors by threading them into the exhaust and tightening to manufacturer specifications (typically around 30-40 lb-ft).
  5. Reconnect the electrical connectors securely.

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

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed), clamps.
• Sub-steps:
  1. Inspect the catalytic converter for physical damage and blockage.
  2. If replacement is needed, use the exhaust pipe cutter to remove the old catalytic converter.
  3. Install the new catalytic converter in the same position, ensuring proper alignment.
  4. Secure it using exhaust clamps and torque them to the manufacturer’s specifications.
  5. Reconnect any exhaust hangers that were removed.

4. Final Checks

• Reconnect the negative battery terminal.
• Clear the P0420 code using the OBD-II scanner.
• Start the engine and let it idle, then take the vehicle for a test drive to ensure proper operation.