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

Solution

1. Preparation

• Gather required tools and parts.
• Ensure the vehicle is parked on a flat surface with the engine off and cool.
• Disconnect the negative battery terminal.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench, penetrating oil
• Apply penetrating oil to the O2 sensor threads if they are rusted.
• Disconnect the electrical connector from the upstream (pre-catalytic) oxygen sensor.
• Use the O2 sensor socket to remove the upstream oxygen sensor.
• Install the new upstream oxygen sensor and torque it to manufacturer specifications (usually around 30 lb-ft).
• Repeat the process for the downstream (post-catalytic) oxygen sensor if necessary.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool
• Remove any necessary components obstructing access to the catalytic converter (e.g., heat shields).
• Disconnect the exhaust piping from the catalytic converter using the socket set.
• Remove the catalytic converter from its mounting points, noting the orientation for installation.
• Install the new catalytic converter, ensuring all gaskets are in place.
• Torque all bolts to manufacturer specifications (typically around 30 lb-ft).

4. Clear Codes and Reconnect Battery

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the engine control unit.