how to fix P0420 code on Honda Accord Eleventh Generation (2023-present)

Solution

1. Preparation

• Gather tools and parts required.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool if it has been running.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, ratchet, torque wrench, penetrating oil (if needed).
• Sub-steps:
  1. Locate the upstream (pre-catalytic) oxygen sensor and the downstream (post-catalytic) oxygen sensor.
  2. Use penetrating oil on the sensor threads if they are corroded.
  3. Disconnect the electrical connector from the oxygen sensor.
  4. Remove the faulty sensor using the O2 sensor socket and ratchet.
  5. Install the new sensor and torque it to the manufacturer’s specification (typically around 30-35 ft-lbs).
  6. Reconnect the electrical connector.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, jack and jack stands, exhaust pipe cutter (if needed).
• Sub-steps:
  1. Raise the vehicle securely with jack stands.
  2. Inspect the catalytic converter for any visible damage or blockage.
  3. If replacement is needed, disconnect the exhaust pipes using the socket set.
  4. Remove any brackets or supports holding the catalytic converter in place.
  5. Install the new catalytic converter, ensuring a proper fit.
  6. Reconnect exhaust pipes and torque to specifications.
  7. Lower the vehicle.