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

Solution

1. Preparation

• Gather tools and parts required.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Using a socket wrench, carefully unscrew the sensors from the exhaust pipes.
3. Inspect the sensor connectors for corrosion or damage; replace if necessary.
4. Install new oxygen sensors, ensuring they are tightened to the manufacturer's torque specifications (typically around 30 ft-lbs).
5. Reconnect the battery.

3. Inspect and Replace Catalytic Converter

1. Confirm that the catalytic converter is faulty (if sensors are good and no exhaust leaks are found).
2. Using a socket set, remove the bolts securing the catalytic converter to the exhaust system.
3. Carefully detach the catalytic converter from the exhaust pipe and the manifold.
4. Inspect the mounting gaskets and replace if worn or damaged.
5. Install a new catalytic converter, ensuring proper alignment with exhaust pipes.
6. Tighten all bolts to the manufacturer's specifications (typically around 30 ft-lbs).
7. Reconnect any sensors that were disconnected.

4. Final Checks

1. Start the engine and let it idle for a few minutes to check for leaks.
2. Ensure all connections are secure and that there are no rattles or unusual noises.
3. Clear the P0420 code from the vehicle’s computer using an OBD-II scanner.