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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a flat surface and the engine is turned off.
• Disconnect the battery to avoid any electrical issues during repairs.

2. Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors on the exhaust system.
  2. Disconnect the electrical connectors from both sensors.
  3. Using the O2 sensor socket, carefully remove the upstream sensor (bank 1 sensor 1) first.
  4. Install the new sensor and torque it to manufacturer's specification (typically around 30 lb-ft).
  5. Repeat the process for the downstream sensor (bank 1 sensor 2).
  6. Reconnect the electrical connectors.

3. Inspect and/or Replace Catalytic Converter

• Tools Required: Jack and jack stands, socket set, exhaust pipe cutter (if necessary), new catalytic converter.
• Sub-steps:
  1. Lift the vehicle using a jack and secure it with jack stands.
  2. Inspect the catalytic converter for physical damage or signs of clogging.
  3. If replacement is needed, unbolt the catalytic converter from the exhaust system using the socket set.
  4. If necessary, use an exhaust pipe cutter to remove the old catalytic converter.
  5. Install the new catalytic converter, ensuring proper alignment with the exhaust system.
  6. Torque the bolts to the manufacturer's specification.
  7. Reconnect any exhaust hangers or supports.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the battery and start the engine.
  2. Use the OBD-II scanner to clear the P0420 code from the system.
  3. Take the vehicle for a test drive to ensure the check engine light does not reappear and monitor for proper performance.