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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool down before working on the exhaust system.

2. Inspect and Replace O2 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 an O2 sensor socket to remove the sensors. Replace them with new, compatible sensors.
  4. Reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. Remove the exhaust heat shield if applicable.
  2. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe using a socket set.
  3. Inspect the old converter for damage or blockage. If damaged, replace it with a new catalytic converter.
  4. Install the new catalytic converter, ensuring proper alignment and sealing.
  5. Torque the bolts to manufacturer specifications (typically around 30-40 ft-lbs).

4. Clear Codes and Test Drive

• Sub-steps:
  1. Reconnect the battery terminals.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Start the engine and let it warm up to operating temperature.
  4. Take the vehicle for a test drive to ensure that the check engine light does not return.