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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent electrical shock.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Remove the upstream oxygen sensor using the O2 sensor socket.
• Inspect the sensor for damage; replace if needed.
• Install the new sensor and torque to manufacturer specifications (typically around 30 ft-lbs).
• Repeat for the downstream oxygen sensor.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust gasket
• Remove the exhaust pipe connected to the catalytic converter using the socket set.
• Inspect the catalytic converter for any physical damage or excessive soot.
• If necessary, remove the catalytic converter by unbolting it from the exhaust manifold and the exhaust pipe.
• Install the new catalytic converter and ensure to use a new exhaust gasket.
• Torque the bolts to manufacturer specifications (usually 25-30 ft-lbs).

4. Reset Engine Codes

• Reconnect the battery.
• Use an OBD-II scanner to clear the P0420 code.
• Start the engine and allow it to reach operating temperature.