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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate Oxygen Sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Unplug the Sensors: Carefully disconnect the electrical connectors from both sensors.
3. Remove the Sensors: Use an oxygen sensor socket to unscrew and remove the sensors.
4. Install New Sensors: Apply anti-seize compound on the threads of the new oxygen sensors and install them in the same locations.
5. Reconnect Electrical Connectors: Securely connect the electrical connectors to the new sensors.

3. Inspect and Replace the Catalytic Converter

1. Remove Exhaust Components: If necessary, remove any exhaust heat shields or brackets to gain access to the catalytic converter.
2. Unbolt the Catalytic Converter: Use a socket set to remove the bolts securing the catalytic converter to the exhaust manifold and exhaust pipe.
3. Inspect Gasket: Check the exhaust gaskets for wear; replace if necessary.
4. Install New Catalytic Converter: Position the new catalytic converter and secure it with bolts. Tighten to manufacturer’s specifications (typically around 24-30 lb-ft).
5. Reinstall Exhaust Components: Replace any heat shields or brackets that were removed.

4. Reconnect Battery and Clear Codes

1. Reconnect the Battery: Reattach the negative battery terminal and ensure a secure connection.
2. Clear Codes: Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.