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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the car battery to ensure safety.
• Ensure the vehicle is on a level surface and securely lifted if necessary.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Find the upstream (pre-catalytic converter) and downstream (post-catalytic converter) O2 sensors.
2. Remove the O2 sensors: Use an O2 sensor socket. Turn counterclockwise to unscrew each sensor.
   • Tools Required: O2 sensor socket, ratchet.
3. Install new O2 sensors: Apply anti-seize compound on the threads and install the new sensors by turning them clockwise.
4. Reconnect the battery.

3. Inspect and Replace Catalytic Converter

1. Remove the catalytic converter:
   • Loosen and remove bolts and clamps connecting the catalytic converter to the exhaust system.
   • Tools Required: Socket set, ratchet, penetrating oil (if bolts are rusted).
2. Install the new catalytic converter: Position the new unit in place and tighten all bolts and clamps to manufacturer specifications (usually around 30-40 lb-ft).
3. Reconnect any exhaust components that may have been removed during the process.

4. Clear Codes and Test

1. Clear the trouble codes: Use the OBD-II scanner to erase the P0420 code.
2. Test drive the vehicle: Drive for at least 20 minutes to allow the engine control module to recheck the system.