why is my Honda Civic 11th Generation (2022-Present) check engine light on with code P0420

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is on a flat surface and securely supported.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream and downstream oxygen sensors on the exhaust system.
2. Unplug the electrical connectors for both sensors.
3. Use an oxygen sensor socket to remove the sensors from the exhaust pipe.
4. Install the new oxygen sensors by threading them into place and tightening to the manufacturer's specifications (usually around 30-40 lb-ft).
5. Reconnect the electrical connectors securely.

3. Inspect and Replace the Catalytic Converter

1. Inspect the catalytic converter visually for any signs of damage or blockage.
2. If replacement is necessary, remove the exhaust pipes connected to the catalytic converter using a socket set.
3. Unbolt the catalytic converter from the exhaust manifold using a wrench.
4. Install the new catalytic converter, ensuring proper alignment and sealing.
5. Torque the bolts to the manufacturer's specifications (typically around 25-35 lb-ft).
6. Reconnect the exhaust pipes and check for leaks.

4. Clear the Error Codes

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 observe if the check engine light remains off.