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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to avoid electrical issues.
• Allow the engine to cool completely before proceeding.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Remove the wiring connector from each oxygen sensor.
  3. Use the O2 sensor socket and ratchet to carefully unscrew the sensors from the exhaust manifold and catalytic converter.
  4. Install the new oxygen sensors by screwing them in place and tightening them to the manufacturer's specified torque (usually around 30 ft-lbs).
  5. Reconnect the wiring connectors to each oxygen sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Wrench set, jack and jack stands, exhaust pipe cutter or saw
• Sub-steps:
  1. Raise the vehicle securely using jack and jack stands.
  2. Inspect the catalytic converter for damage or blockage.
  3. If replacement is necessary, use an exhaust pipe cutter or saw to remove the old catalytic converter from the exhaust system.
  4. Install the new catalytic converter by fitting it into place and securing it with proper hardware (follow the manufacturer's specifications for torque).
  5. Reconnect any exhaust hangers that were removed.

4. Clear Codes and Test Drive

• 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 vehicle’s memory.
  3. Start the engine and check for leaks in the exhaust system.
  4. Test drive the vehicle under various driving conditions to ensure the check engine light does not reappear.