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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to avoid any electrical shorts.
• Allow the exhaust system to cool if the vehicle has been running.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Unplug the electrical connectors from both sensors.
  3. Use an oxygen sensor socket to remove the sensors from the exhaust manifold and catalytic converter.
  4. Install new oxygen sensors by screwing them in place and reconnecting the electrical connectors.
• Tools Required: Oxygen sensor socket, wrench set, torque wrench.
• Safety Warnings: Ensure the exhaust system is cool to prevent burns.

3. Inspect and Replace the Catalytic Converter

• Sub-steps:
  1. Remove the exhaust pipes leading to and from the catalytic converter by loosening the bolts or clamps.
  2. Remove the catalytic converter from the vehicle.
  3. Inspect the catalytic converter for signs of physical damage or excessive soot buildup.
  4. Install a new catalytic converter, ensuring all gaskets and seals are in place.
  5. Reattach the exhaust pipes and tighten all bolts to the manufacturer’s torque specifications.
• Tools Required: Socket set, torque wrench, gasket scraper.
• Safety Warnings: Ensure the vehicle is securely lifted if working under it.

4. Clear the Codes and Test Drive

• 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 let it idle for a few minutes.
  4. Take the vehicle for a test drive to ensure that the check engine light does not reappear and that performance is restored.