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

Solution

1. Preparation

• Gather tools and parts.
• Ensure the vehicle is parked on a level surface with the engine off and cooled down.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, socket wrench, anti-seize compound.
• Remove the upstream (pre-catalytic) oxygen sensor by using the O2 sensor socket.
• Inspect the sensor for damage and replace it if necessary.
• Apply anti-seize compound to the threads of the new sensor before installation.
• Install the new upstream oxygen sensor and reconnect the wiring.
• Repeat the process for the downstream (post-catalytic) oxygen sensor if it shows signs of failure.

3. Inspect and Replace the Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter or reciprocating saw (if necessary).
• Remove the exhaust hangers and bolts connecting the catalytic converter to the exhaust system.
• Carefully detach the catalytic converter from the exhaust system; be cautious of any remaining exhaust components.
• Inspect the old catalytic converter for physical damage, clogging, or contamination.
• Install the new catalytic converter, ensuring proper alignment with the exhaust system.
• Secure it with new gaskets and bolts, torquing to the manufacturer’s specifications.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code from the ECM.
• Start the engine and let it idle for a few minutes.