how to fix P0420 code in Honda Civic 9th Generation (2012-2015)

Solution

1. Preparation

• Gather all tools and parts required for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the engine is cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors on the exhaust manifold and catalytic converter, respectively.
  2. Disconnect the electrical connectors from both sensors.
  3. Use the O2 sensor socket to remove the upstream sensor first, followed by the downstream sensor.
  4. Install the new sensors by threading them into place and tightening to the manufacturer's specifications (typically around 30 ft-lbs).
  5. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torch, exhaust hanger removal tool, gaskets.
• Sub-steps:
  1. Remove the exhaust heat shield, if applicable, to access the catalytic converter.
  2. Disconnect any exhaust pipes from the catalytic converter using the socket set.
  3. Remove the catalytic converter from its mounts using the exhaust hanger removal tool.
  4. Install the new catalytic converter, ensuring correct alignment with the exhaust system.
  5. Reattach any disconnected exhaust pipes and torque to specifications.
  6. Reinstall the heat shield, if applicable.

4. Reset the Engine Control Module (ECM)

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use an OBD-II scanner to clear any stored trouble codes from the ECM.
  3. Start the engine and allow it to idle for a few minutes to check for any reoccurring codes.