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

Solution

1. Preparation

• Gather tools and parts required for repair.
• Safety gear: gloves and safety glasses.
• Ensure the vehicle is parked on a flat surface, and the engine is cool.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, torque wrench, ratchet, and extensions.
• Disconnect the negative battery terminal to avoid electrical shorts.
• Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Use the O2 sensor socket to remove the sensors from the exhaust manifold and catalytic converter.
• Install the new sensors, tightening to the manufacturer's specified torque (typically around 30 lb-ft).
• Reconnect the negative battery terminal.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack and jack stands, exhaust cutter, and sealing materials.
• Raise the vehicle using a jack and secure it with jack stands.
• Remove the exhaust system components connected to the catalytic converter using a socket set.
• Inspect the catalytic converter for any signs of clogging or damage.
• If replacement is needed, cut out the old catalytic converter using the exhaust cutter.
• Install the new catalytic converter, ensuring proper alignment and sealing with exhaust gaskets.
• Reattach the exhaust components in reverse order of removal.

4. Clear Error Codes and Test

• Use an OBD-II scanner to clear the P0420 code.
• Start the engine and allow it to reach normal operating temperature.
• Take the vehicle for a test drive to ensure the check engine light does not reappear and monitor performance.