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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a level surface with the engine off.
• Disconnect the negative battery terminal to reset the system.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Using a socket wrench, carefully remove the upstream oxygen sensor.
3. Install the new oxygen sensor, ensuring it is tightened to manufacturer specifications (typically around 30 Nm).
4. Repeat the process for the downstream oxygen sensor if it is also faulty.
5. Reconnect the battery terminal.

3. Inspect and Replace Catalytic Converter

1. If the oxygen sensors are functioning correctly, inspect the catalytic converter for damage or blockage.
2. Remove the exhaust system components as necessary to access the catalytic converter (this may involve removing bolts or clamps).
3. Detach the catalytic converter from the exhaust manifold and exhaust pipe.
4. Install the new catalytic converter, ensuring proper alignment and sealing.
5. Tighten all bolts and clamps to the manufacturer’s torque specifications (typically around 40-60 Nm for exhaust components).

4. Clear Codes and Test

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear any existing error codes from the vehicle's computer.
3. Start the engine and allow it to idle for a few minutes.
4. Take the vehicle for a test drive to ensure the check engine light does not reappear.