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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on the vehicle.
• Allow the engine to cool down completely before starting the repair.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet and extension.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors connected to the exhaust system.
  2. Unplug the electrical connectors from both sensors.
  3. Use the O2 sensor socket to remove the sensors from the exhaust manifold (upstream) and catalytic converter (downstream).
  4. Install the new oxygen sensors by screwing them into their respective locations and tightening them to the manufacturer's torque specification.
  5. Reconnect the electrical connectors to the new sensors.

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

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if applicable).
• Sub-steps:
  1. If the oxygen sensors are functioning correctly but the P0420 code persists, remove the catalytic converter from the exhaust system.
  2. Use an exhaust pipe cutter if the converter is welded in place or a socket set to unbolt it from the exhaust pipes.
  3. Inspect the catalytic converter for blockages or physical damage.
  4. Install a new catalytic converter by reversing the removal process. Ensure all bolts are tightened to the manufacturer's specifications.
  5. If using a universal converter, ensure it meets emissions standards for your region.

4. Clear Codes and Test

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle's memory.
  3. Start the engine and allow it to reach operating temperature.
  4. Take the vehicle for a test drive to verify that the check engine light does not reappear.