how to fix P0420 code on Honda Civic 9th Generation (2012-2015)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the parking brake is applied.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors: Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) O2 sensors.
2. Remove the Sensors: Use an O2 sensor socket or wrench to unscrew and remove both sensors.
3. Inspect for Damage: Check the sensors for signs of wear, corrosion, or damage.
4. Install New Sensors: If needed, install new oxygen sensors (ensure they are the correct type for your model). Torque to manufacturer specifications (typically around 30 lb-ft).
5. Reconnect the Battery: Reconnect the battery after the O2 sensors have been replaced.

3. Inspect and Clean/Replace Catalytic Converter

1. Examine the Catalytic Converter: Check for rattling sounds (indicating internal damage) and look for signs of overheating or physical damage.
2. Clean the Catalytic Converter: If the converter is clogged but not damaged, use a catalytic converter cleaner following the product instructions.
3. Replace the Catalytic Converter: If damaged, remove the old catalytic converter by unbolting it from the exhaust system.
4. Install New Catalytic Converter: Position the new catalytic converter and secure it with bolts. Torque to manufacturer specifications (typically around 30 lb-ft).

4. Test the System

• Start the vehicle and allow it to reach operating temperature.
• Use the OBD-II scanner to clear the P0420 code and check if it returns after a test drive.