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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Using a socket wrench, carefully remove the upstream oxygen sensor from the exhaust manifold.
   • Tools Required: Oxygen sensor socket, socket wrench
3. Install the new upstream oxygen sensor and torque it to manufacturer specifications (usually around 30 ft-lbs).
4. Repeat the process for the downstream oxygen sensor if it is found to be faulty, using the same torque specifications.

3. Inspect and Replace Catalytic Converter (if necessary)

1. If the catalytic converter is damaged, loosen the clamps or bolts securing it to the exhaust system.
   • Tools Required: Socket set, ratchet
2. Remove the old catalytic converter and install the new unit, ensuring it fits securely and is aligned correctly.
3. Reattach any clamps or bolts and torque them to specifications (typically around 30-40 ft-lbs).

4. Final Checks

1. Reconnect the negative battery terminal.
2. Clear the error codes using the OBD-II scanner.
3. Start the engine and let it idle to check for leaks and ensure proper operation.