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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to ensure safety while working on the electrical components.
• Allow the engine to cool before starting work.

2. Replace Faulty Oxygen Sensors (if applicable)

• Tools Required: O2 sensor socket, wrench set, penetrating oil (if necessary)
• Spray penetrating oil on the oxygen sensor threads and let it sit for a few minutes.
• Disconnect the electrical connectors of the old sensors.
• Use the O2 sensor socket to remove the upstream and/or downstream oxygen sensors.
• Install the new sensors by threading them into place and tightening to the manufacturer's specifications (typically around 30 ft-lbs).
• Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter, gasket scraper
• Loosen the exhaust clamp or bolts securing the catalytic converter to the exhaust pipe and the header.
• Carefully remove the catalytic converter from the exhaust system. If necessary, cut the exhaust pipes using the exhaust pipe cutter.
• Clean the mating surfaces of the exhaust pipes to ensure a good seal for the new catalytic converter.
• Install the new catalytic converter, ensuring proper alignment with the exhaust system.
• Tighten the bolts or clamps to the manufacturer's torque specifications.

4. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
• Test drive the vehicle for at least 15-20 minutes to ensure the check engine light does not reappear and that performance is restored.