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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, jack and jack stands, socket set, torque wrench, oxygen sensor socket.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the pre-catalytic and post-catalytic oxygen sensors.
  2. Use the oxygen sensor socket to carefully remove the sensors.
  3. Check the wiring and connectors for any damage or corrosion; repair as necessary.
  4. Install new oxygen sensors, ensuring they are properly torqued (typically 30-40 ft-lbs).
  5. Reconnect the negative battery terminal.

3. Inspect and Replace Catalytic Converter (if needed)

• Sub-steps:
  1. Safely raise the vehicle using a jack and secure it with jack stands.
  2. Remove the exhaust heat shield to access the catalytic converter.
  3. Unbolt the catalytic converter from the exhaust pipe and the exhaust manifold, taking care to collect any gaskets.
  4. Inspect the catalytic converter for signs of damage or clogging.
  5. Install the new catalytic converter with new gaskets, ensuring all bolts are torqued to manufacturer specifications (typically 25-30 ft-lbs).
  6. Replace the exhaust heat shield.

4. Final Checks

• Sub-steps:
  1. Start the engine and let it idle for a few minutes, checking for leaks around the exhaust connections.
  2. Clear the P0420 code using the OBD-II scanner.
  3. Take the vehicle for a test drive to ensure that the check engine light does not reappear.