how to fix P0420 code on my Honda Civic 11th Generation (2022-Present)

Solution

1. Preparation

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

2. Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, ratchet, torque wrench, penetrating oil
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors (typically found before and after the catalytic converter).
  2. Apply penetrating oil to the sensor threads and allow it to sit for a few minutes.
  3. Using the O2 sensor socket and ratchet, carefully unscrew the sensor from the exhaust pipe.
  4. Install the new oxygen sensor by screwing it into place and tightening to the manufacturer’s torque specifications (usually around 30 lb-ft).
  5. Reconnect the electrical connector.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, exhaust pipe cutter, jack and jack stands, new gasket (if required)
• Sub-steps:
  1. Lift the vehicle securely using a jack and jack stands.
  2. Unbolt the catalytic converter from the exhaust system using the socket set.
  3. Inspect the old catalytic converter for any physical damage or excessive carbon buildup.
  4. If the catalytic converter is damaged, remove it completely and clean the mounting surfaces.
  5. Install the new catalytic converter with a new gasket (if applicable) and tighten the bolts to the manufacturer’s specifications.
  6. Lower the vehicle back to the ground.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner
• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the ECM.
  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 and monitor performance.