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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is on a level surface, and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: Oxygen sensor socket, wrench set, multimeter.
• Remove the upstream (pre-catalytic) oxygen sensor using the oxygen sensor socket.
  • Sub-steps:
    1. Disconnect the electrical connector of the oxygen sensor.
    2. Use the oxygen sensor socket to unscrew the sensor from the exhaust manifold.
• Inspect the sensor for damage; replace if necessary.
• Install the new upstream oxygen sensor and reconnect the electrical connector.
• Repeat the process for the downstream (post-catalytic) oxygen sensor if needed.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool.
• If the catalytic converter is damaged or clogged, remove it for replacement.
  • Sub-steps:
    1. Use the socket set to remove bolts securing the catalytic converter to the exhaust system.
    2. Disconnect any exhaust hangers using the exhaust hanger removal tool.
    3. Remove the old catalytic converter from the vehicle.
    4. Install the new catalytic converter, ensuring proper alignment.
    5. Torque the bolts to the manufacturer’s specifications (typically around 30-40 ft-lbs).
• Reconnect any exhaust hangers.

4. Reset the Engine Control Module (ECM)

• Reconnect the battery and use the OBD-II scanner to clear the P0420 code.