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 flat surface and the ignition is off.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Remove the oxygen sensors:
   • Use an oxygen sensor socket or a wrench to carefully unscrew the sensors from their locations.
   • Take note of the wiring orientation for reinstallation.
3. Install new oxygen sensors:
   • Apply anti-seize compound to the threads of the new sensors (if applicable).
   • Torque the sensors to the manufacturer’s specifications (typically around 30 lb-ft).
4. Reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove the exhaust components:
   • Loosen and remove any bolts or clamps securing the catalytic converter to the exhaust system.
   • Carefully detach the catalytic converter from the vehicle.
2. Inspect the catalytic converter:
   • Check for physical damage, such as dents or cracks, or signs of excessive carbon build-up.
3. Install the new catalytic converter:
   • Position the new catalytic converter and secure it with the original bolts or new nuts and bolts.
   • Torque to manufacturer specifications, typically around 30 lb-ft.
4. Reattach the exhaust components, ensuring all connections are tight.

4. Clear Codes and Test

1. Reconnect the battery.
2. Use the OBD-II scanner to clear the P0420 code.
3. Start the vehicle and allow it to reach operating temperature.
4. Take the vehicle for a test drive to ensure the check engine light does not reappear.