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

Solution

1. Preparation

• Gather tools and parts necessary for the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Use an O2 sensor socket to carefully remove the upstream oxygen sensor.
3. Install the new upstream oxygen sensor and tighten it to manufacturer specifications (typically around 30-33 lb-ft).
4. Repeat the process for the downstream oxygen sensor if needed.

3. Inspect and Replace Catalytic Converter

1. If the catalytic converter is suspected to be faulty, remove the exhaust heat shield and any necessary brackets.
2. Disconnect the exhaust pipes from the catalytic converter using a socket set.
3. Remove the catalytic converter from the exhaust manifold and the mid-pipe.
4. Install the new catalytic converter, ensuring proper alignment and fitment.
5. Reattach the exhaust pipes and tighten bolts to manufacturer specifications (typically around 30-40 lb-ft).
6. Reinstall the exhaust heat shield and associated components.

4. Final Checks

1. Reconnect the negative battery terminal.
2. Clear the P0420 code using the OBD-II scanner.
3. Start the engine and let it idle for a few minutes, checking for leaks around the exhaust connections.