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

Solution

1. Preparation

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

2. Inspect and Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter.
• Remove the upstream (pre-catalytic) oxygen sensor using a socket wrench.
• Use a multimeter to test the sensor’s voltage output. A healthy sensor should fluctuate between 0.1V and 0.9V.
• If the sensor is faulty, replace it with a new one.

3. Inspect the Catalytic Converter

• Tools Required: Jack and jack stands, socket set.
• Raise the vehicle securely on jack stands.
• Visually inspect the catalytic converter for damage or blockage.
• If physical damage is found, replace the catalytic converter.

4. Repair Exhaust Leaks

• Inspect all joints and connections in the exhaust system.
• Tighten loose bolts or replace gaskets as necessary.
• Use exhaust sealant or clamps to fix minor leaks.

5. Clear Codes and Test

• Reconnect the battery's negative terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and let it run for a few minutes.
• Perform a test drive to ensure the vehicle operates normally without triggering the check engine light.