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 battery to ensure safety while working on electrical components.
• Raise the vehicle securely on jack stands.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the wiring harness from both oxygen sensors.
  3. Use an oxygen sensor socket to remove the sensors from the exhaust manifold and catalytic converter.
  4. Install new oxygen sensors (ensure they are the correct type for your model).
  5. Reconnect the wiring harness securely.

Tools Required:

• OBD-II scanner
• Oxygen sensor socket
• Torque wrench
• Infrared thermometer

3. Inspect and Replace Catalytic Converter

• Sub-steps:
  1. Check for any exhaust leaks around the catalytic converter and exhaust joints.
  2. If damaged, unbolt the catalytic converter from the exhaust system (may require a socket set).
  3. Remove any mounting brackets or heat shields if necessary.
  4. Install the new catalytic converter in the reverse order of removal, ensuring all gaskets and seals are replaced.
  5. Torque the bolts to the manufacturer's specifications.

Tools Required:

• Socket set
• Torque wrench
• Gasket scraper (if needed)