how to fix P0420 code in my Honda Accord 10th Generation (2018-2022)

Solution

1. Preparation

• Gather tools and parts needed for repairs.
• Disconnect the battery to prevent electrical issues.
• Allow the engine to cool completely before starting work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Remove the upstream oxygen sensor (before the catalytic converter) and the downstream sensor (after the catalytic converter).
  • Use the O2 sensor socket and ratchet to unscrew the sensors.
• Inspect the sensors for damage or excessive carbon buildup; replace them if needed.
  • Torque the new sensors to the manufacturer’s specified value (usually around 30-50 lb-ft).

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, wrench set, exhaust gasket, jack stands
• Raise the vehicle securely and support it with jack stands.
• Remove any heat shields or brackets obstructing access to the catalytic converter.
• Unbolt the catalytic converter from the exhaust system (both upstream and downstream connections).
• Replace with a new catalytic converter, ensuring correct alignment and fit.
  • Use new exhaust gaskets to prevent leaks.
  • Torque the bolts to the specified values (check the service manual for specifics).

4. Clear Codes and Test Drive

• Reconnect the battery and use the OBD-II scanner to clear any stored trouble codes.
• Start the engine and allow it to reach operating temperature.
• Take the vehicle for a test drive to ensure that the check engine light does not reappear and monitor for any unusual symptoms.