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

Solution

1. Preparation

• Gather all necessary tools and parts.
• 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

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Steps:
  1. Locate the upstream (pre-catalytic) oxygen sensor near the exhaust manifold.
  2. Disconnect the electrical connector from the oxygen sensor.
  3. Use the O2 sensor socket to remove the sensor from the exhaust pipe.
  4. Install the new oxygen sensor, tightening it to the manufacturer’s specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connector.
  6. Repeat the process for the downstream (post-catalytic) oxygen sensor if necessary.

3. Inspect and Replace Catalytic Converter (if needed)

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter or saw
• Steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Disconnect the exhaust pipe before the catalytic converter using a socket set.
  3. Cut the exhaust pipe if necessary to remove the old catalytic converter.
  4. Install the new catalytic converter, ensuring proper alignment.
  5. Reattach the exhaust pipe and secure all clamps and bolts.
  6. Lower the vehicle back to the ground.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner
• Steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
  3. Start the engine and allow it to reach operating temperature.
  4. Take the vehicle for a test drive to ensure proper operation and verify that the check engine light does not reappear.