how to fix P0420 error code in Honda Civic 11th Generation (2022-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent any electrical shorts.
• Allow the engine to cool before starting repairs.

2. Inspect and Repair Exhaust System

• Sub-steps:
  • Visually inspect the exhaust system for any signs of leaks, cracks, or rust.
  • If any damage is found, replace the affected sections of the exhaust system.

3. Replace Oxygen Sensors

• Sub-steps:
  • Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  • Use a socket wrench to remove the sensors. Make sure to note their positions.
  • Apply anti-seize compound on the threads of the new sensors (if recommended).
  • Install the new sensors and torque to manufacturer specifications (typically around 30 lb-ft).

4. Replace Catalytic Converter (if necessary)

• Sub-steps:
  • Remove any bolts or clamps securing the catalytic converter to the exhaust.
  • Carefully detach the old catalytic converter from the exhaust system.
  • Install the new catalytic converter, ensuring a proper fit and sealing.
  • Torque all bolts to the manufacturer’s specifications.

5. Reset the Engine Control Module (ECM)

• Sub-steps:
  • Reconnect the battery.
  • Use an OBD-II scanner to clear the error codes from the ECM.
  • Start the engine and allow it to idle for a few minutes.