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

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Using a socket wrench, carefully remove both oxygen sensors.
3. Inspect the sensors for carbon buildup or damage. Replace any faulty sensors with new ones.
4. Install the new sensors and torque them to manufacturer's specifications (typically around 30 lb-ft).

3. Inspect and Replace Catalytic Converter

1. If the oxygen sensors are functioning correctly, proceed to inspect the catalytic converter.
2. Remove any heat shields or mounting brackets obstructing access to the catalytic converter.
3. Use a wrench to unfasten the bolts connecting the catalytic converter to the exhaust system.
4. Carefully remove the old catalytic converter.
5. Install the new catalytic converter, ensuring proper alignment with the exhaust pipes.
6. Secure with bolts and torque to manufacturer specifications (check service manual for exact torque values).

4. Reconnect Battery and Reset ECU

1. Reconnect the vehicle battery.
2. Use the OBD-II scanner to clear the error codes from the ECU.
3. Start the engine and allow it to idle for a few minutes.