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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative terminal of the battery to prevent electrical shorts.
• Allow the vehicle to cool completely before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench, penetrating oil.
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Apply penetrating oil to the sensor threads if necessary to avoid damage.
  3. Disconnect the electrical connectors from both oxygen sensors.
  4. Remove the sensors using the O2 sensor socket.
  5. Install new oxygen sensors in reverse order, tightening to the manufacturer's specified torque (usually around 30-35 ft-lbs).

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, wrench set, exhaust pipe cutter, gasket scraper, new gasket/material.
• Sub-steps:
  1. Inspect the catalytic converter for signs of damage or clogging.
  2. If replacement is needed, remove the exhaust pipe connected to the catalytic converter using a socket set.
  3. Cut the exhaust pipe if it’s too corroded or difficult to remove.
  4. Remove the old catalytic converter and clean the mounting area.
  5. Install the new catalytic converter with a new gasket, securing it with the appropriate hardware (torque to specifications).
  6. Reconnect the exhaust pipe.

4. Clear Codes and Test

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the system.
  3. Start the engine and let it idle for a few minutes before performing a test drive.