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

Solution

1. Preparation

• Gather tools and parts needed.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool completely before starting work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter.
• Remove the upstream oxygen sensor from the exhaust manifold using the O2 sensor socket.
• Inspect the sensor for damage or contamination. If faulty, replace it with a new one.
• Repeat the process for the downstream oxygen sensor, ensuring the connector is clean and secure.

3. Examine the Catalytic Converter

• Tools Required: Jack and jack stands or ramps, socket set.
• Raise the vehicle using a jack and secure it with jack stands.
• Visually inspect the catalytic converter for signs of physical damage or blockage.
• If the converter is damaged or clogged, remove it by unbolting it from the exhaust system. Use a socket set for this task.
• Replace the catalytic converter with a new, OEM-spec unit.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner.
• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and conduct a test drive to ensure the vehicle operates normally and the check engine light does not reappear.