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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool completely before proceeding with repairs.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket or wrench, multimeter
• Sub-steps:
  1. Locate the pre-catalytic and post-catalytic oxygen sensors; these are typically found in the exhaust pipe.
  2. Use the O2 sensor socket to carefully remove the old sensors.
  3. Check the wiring and connectors for any damage; repair or replace as needed.
  4. Install new oxygen sensors, ensuring they are tightened to the manufacturer's specifications (usually around 30 lb-ft).
  5. Reconnect the battery terminal.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed), gaskets
• Sub-steps:
  1. Remove the exhaust pipe connecting to the catalytic converter using the socket set.
  2. If necessary, cut the exhaust pipe using an exhaust pipe cutter to remove the old catalytic converter.
  3. Inspect the mounting bracket and replace if damaged.
  4. Install the new catalytic converter, ensuring proper alignment and using new gaskets for a secure seal.
  5. Tighten all bolts to the manufacturer's torque specifications (typically around 20-30 lb-ft).
  6. Reconnect any sensors or pipes that were removed during the installation process.