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

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts during repair.
• Allow the exhaust system to cool before working on it.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Use a wrench or socket to remove the oxygen sensors from the exhaust system.
  4. Install new oxygen sensors, ensuring they are torqued to manufacturer specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connectors securely.

3. Check and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. Inspect the catalytic converter for any signs of physical damage or rattling noises.
  2. If the converter is damaged, remove it by unbolting it from the exhaust pipe using a socket set.
  3. Clean the exhaust pipe flanges to ensure a good seal for the new catalytic converter.
  4. Install the new catalytic converter, tightening bolts to the manufacturer's torque specifications (typically around 30-40 lb-ft).
  5. Reconnect any heat shields or brackets that were removed.

4. Clear Codes and Test

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use an OBD-II scanner to clear the P0420 code from the vehicle's computer.
  3. Start the engine and allow it to reach operating temperature.
  4. Take the vehicle for a test drive to ensure the check engine light does not return.