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

Solution

1. Preparation

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

2. Inspect and Replace Faulty Oxygen Sensors

1. Locate the Oxygen Sensors: Find the upstream and downstream oxygen sensors on the exhaust manifold and catalytic converter.
2. Remove the Sensors:
   • Use an oxygen sensor socket or wrench to carefully unscrew the sensors.
   • Disconnect the electrical connectors from the sensors.
3. Install New Sensors:
   • Apply anti-seize compound to the threads of the new sensors.
   • Install the new sensors by hand and tighten them to manufacturer specifications (usually around 30-40 ft-lbs).
   • Reconnect the electrical connectors.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Check for Physical Damage: Inspect the catalytic converter for any visible signs of damage or blockage.
2. Remove the Catalytic Converter:
   • Loosen the bolts or nuts securing the converter to the exhaust system using a socket set.
   • Carefully detach the converter from the exhaust pipes.
3. Install New Catalytic Converter:
   • Position the new catalytic converter in place and secure it with bolts/nuts.
   • Ensure all gaskets are properly seated to prevent exhaust leaks.

4. Clear the Codes and Test Drive

1. Reconnect the Battery: Once repairs are complete, reconnect the battery.
2. Clear Codes: Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
3. Test Drive: Drive the vehicle for at least 20-30 minutes to allow the system to re-evaluate the catalytic converter's performance.