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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.
• Raise the vehicle and secure it with jack stands.

2. Inspect Oxygen Sensors

• Sub-steps:
  • Locate the upstream and downstream oxygen sensors.
  • Disconnect the electrical connectors from both sensors.
  • Use a multimeter to check the voltage output of the upstream sensor (typically 0.1 to 0.9 volts fluctuating).
  • Replace the oxygen sensor if it is outside the specified range.
• Tools Required: Multimeter

3. Replace Catalytic Converter

• Sub-steps:
  • Remove the heat shield, if applicable, by unscrewing any fasteners.
  • Unbolt the catalytic converter from the exhaust system, starting with the flange bolts.
  • Install the new catalytic converter, ensuring proper alignment.
  • Torque the bolts to manufacturer specifications (typically around 30-40 lb-ft, but check the specific value).
• Tools Required: Socket set, torque wrench

4. Reconnect Electrical Connectors

• Sub-steps:
  • Reconnect the upstream and downstream oxygen sensors.
  • Ensure all connections are secure and free of corrosion.

5. Reconnect Battery and Test

• Sub-steps:
  • Reconnect the negative battery terminal.
  • Start the engine and let it idle for a few minutes.
  • Conduct a test drive under various conditions to ensure the check engine light does not reappear.
• Safety Warnings: Ensure the vehicle is cool before working on exhaust components to avoid burns.