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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to avoid electrical shorts during repairs.
• Allow the engine to cool down before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Remove the upstream oxygen sensor:
  • Locate the upstream O2 sensor before the catalytic converter.
  • Use the O2 sensor socket to unscrew the sensor.
  • Inspect the sensor for damage; replace if necessary.
• Install the new upstream oxygen sensor:
  • Apply anti-seize compound to the threads of the new sensor (if applicable).
  • Torque to manufacturer's specifications (usually around 30 lb-ft).
• Repeat the process for the downstream O2 sensor if it's also faulty.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Jack and jack stands, socket set, exhaust sealant, torque wrench
• Remove the catalytic converter:
  • Raise the vehicle and support it securely on jack stands.
  • Disconnect the exhaust pipes from the catalytic converter using a socket set.
  • Remove any mounting bolts or clamps holding the catalytic converter in place.
• Install the new catalytic converter:
  • Position the new catalytic converter and secure it with mounting bolts.
  • Reconnect the exhaust pipes and ensure all connections are tight.
  • Apply exhaust sealant as needed to prevent leaks.
  • Torque all bolts to the manufacturer's specifications.

4. Final Steps

• Reconnect the negative battery terminal.
• Clear the error codes using the OBD-II scanner.
• Start the engine and allow it to reach operating temperature.