what does code P0420 mean on my Honda Civic 11th Generation (2022-Present) and how to fix it?

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery by removing the negative terminal.

2. Replace Faulty Oxygen Sensors

1. Locate the upstream and downstream oxygen sensors (typically located before and after the catalytic converter).
2. Using a socket wrench, carefully unscrew the faulty oxygen sensors.
3. Install the new oxygen sensors in the reverse order of removal, ensuring they are tightened to the manufacturer's specifications (usually around 30 ft-lbs).
4. Reconnect the electrical connectors for the sensors.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove the exhaust system components leading to the catalytic converter (e.g., bolts, clamps).
2. Disconnect any sensors or heat shields attached to the catalytic converter.
3. Remove the catalytic converter by unbolting it from the exhaust manifold and exhaust pipe.
4. Install the new catalytic converter, ensuring proper alignment.
5. Reattach any sensors or heat shields, and tighten all bolts to the manufacturer's torque specifications.

4. Reset Engine Control Module (ECM)

1. Reconnect the battery by attaching the negative terminal.
2. Use the OBD-II scanner to clear the P0420 code from the ECM.
3. Drive the vehicle for a short distance to monitor for the return of the check engine light.