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

Solution

1. Preparation

• Gather tools and parts.
• Ensure the vehicle is parked on a flat, stable surface.
• Disconnect the negative battery terminal to prevent electrical issues.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Remove the Oxygen Sensors:
   • Use an oxygen sensor socket or wrench.
   • Carefully unscrew both sensors, noting their positions.
3. Install New Oxygen Sensors:
   • Apply anti-seize compound on the threads of the new sensors.
   • Install and tighten to manufacturer specifications (usually around 30 ft-lbs).
4. Reconnect the Battery: Reconnect the negative battery terminal.

3. Check and Replace Catalytic Converter (if necessary)

1. Remove Exhaust Components:
   • Use a socket set to remove any bolts connecting the exhaust to the catalytic converter.
   • Carefully detach the catalytic converter from the exhaust system.
2. Inspect the Catalytic Converter:
   • Check for any signs of physical damage, clogging, or contamination.
3. Install New Catalytic Converter:
   • Position the new catalytic converter in place.
   • Secure with bolts to the manufacturer's torque specifications (typically 30-40 ft-lbs).
4. Reinstall Exhaust Components:
   • Reattach any exhaust pipes or components removed during installation.

4. Clear Codes and Test Drive

1. Clear the Codes: Use the OBD-II scanner to clear the P0420 code.
2. Test Drive: Drive the vehicle for at least 20 minutes under various conditions to ensure the check engine light does not reappear.