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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to ensure safety.
• Allow the exhaust system to cool down before starting work.

2. Replace the Oxygen Sensors

1. Locate the Sensors: Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Remove the Sensors: Use an oxygen sensor socket or wrench to carefully unscrew the sensors. Avoid damaging the sensor wiring.
3. Install New Sensors: Apply anti-seize compound to the threads of the new sensors. Install the new sensors by hand initially, then tighten to the manufacturer’s specifications (usually around 30-40 ft-lbs).
4. Reconnect Electrical Connectors: Ensure that the connectors for the new sensors are securely attached.

3. Check and Repair Exhaust System

1. Inspect for Damage: Examine the catalytic converter and exhaust pipes for any signs of rust, cracks, or leaks.
2. Repair or Replace Components: If any damage is found, replace the affected exhaust components as necessary. Ensure all connections are tight and leak-free.

4. Clear the Code

1. Reconnect Battery: Reconnect the negative battery terminal.
2. Clear Codes: Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
3. Test Drive: Take the vehicle for a test drive to ensure the issue is resolved and check if the check engine light reappears.