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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, multimeter.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors on the exhaust manifold and catalytic converter.
  2. Unplug the electrical connectors from both sensors.
  3. Use the O2 sensor socket to remove the upstream and downstream sensors.
  4. Install new sensors by threading them into their respective locations and tightening them to the manufacturer's specified torque (usually around 30 ft-lbs).
  5. Reconnect the electrical connectors to both sensors.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, exhaust pipe cutter, gasket scraper, torque wrench.
• Sub-steps:
  1. Use the socket set to unbolt the catalytic converter from the exhaust manifold and the exhaust pipe.
  2. If necessary, cut the exhaust pipe using an exhaust pipe cutter.
  3. Clean the mating surfaces on both the manifold and exhaust pipe with a gasket scraper to remove old gasket material.
  4. Install the new catalytic converter, ensuring proper orientation.
  5. Bolt the catalytic converter back to the exhaust manifold and exhaust pipe, tightening to the manufacturer's torque specifications.

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 engine control unit (ECU).
  3. Start the engine and let it reach operating temperature.
  4. Take the vehicle for a test drive to ensure the check engine light does not reappear.