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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
• Tools Required: Oxygen sensor socket, ratchet, and extension.
• Steps:
  1. Remove the upstream oxygen sensor using the oxygen sensor socket.
  2. Install the new upstream oxygen sensor and torque it to the manufacturer's specification (typically around 30 lb-ft).
  3. Repeat the process for the downstream oxygen sensor.

3. Inspect the Catalytic Converter

• Perform a thorough examination of the catalytic converter.
• Steps:
  1. Check for any rattling sounds indicating internal failure.
  2. If damaged, remove the catalytic converter by unbolting it from the exhaust system.
  3. Replace it with a new catalytic converter, ensuring all gaskets and seals are intact.
  4. Torque all bolts to the manufacturer's specifications.

4. Clear Codes and Test

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Steps:
  1. Start the engine and allow it to reach operating temperature.
  2. Take the vehicle for a test drive to ensure the check engine light does not reappear.