how to fix P0420 code in Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Ensure the vehicle is on a level surface and secure it with wheel chocks.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter.
• Remove the upstream (pre-catalytic converter) oxygen sensor using the O2 sensor socket.
• Inspect the sensor for damage; replace if necessary.
• Repeat the process for the downstream (post-catalytic converter) oxygen sensor.
• Reconnect both sensors and ensure they are secure.

3. Inspect and Replace Catalytic Converter (if needed)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary).
• Remove any heat shields or brackets obstructing access to the catalytic converter.
• Unbolt the catalytic converter from the exhaust system, starting with the bolts at the manifold and then the ones at the exhaust pipe.
• Inspect the catalytic converter for internal damage or blockage. If faulty, replace it with a new unit.
• Install the new catalytic converter and torque the bolts to the manufacturer’s specifications (typically around 30-50 lb-ft, but check the service manual for exact values).
• Reinstall any heat shields or brackets.

4. Clear the DTC

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code from the vehicle’s memory.