how to fix P0420 code on Honda Civic 11th Generation (2022-Present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, jack and jack stands.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Inspect and Replace Oxygen Sensors

1. Disconnect the negative battery terminal to prevent electrical shorts.
2. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
3. Using a socket, remove the upstream oxygen sensor.
4. Install the new upstream oxygen sensor and torque it to the manufacturer's specifications (typically 30-40 lb-ft).
5. Repeat the process for the downstream oxygen sensor if it shows signs of malfunction.
6. Reconnect the negative battery terminal.

3. Inspect and Replace Catalytic Converter (if necessary)

1. If the catalytic converter is determined to be faulty, elevate the vehicle using a jack and secure it with jack stands.
2. Remove the exhaust heat shield by unscrewing the bolts.
3. Disconnect the exhaust pipes from the catalytic converter using a socket set, noting their arrangement for reinstallation.
4. Remove the catalytic converter from its mounting brackets.
5. Install the new catalytic converter and secure it in place, ensuring proper alignment with exhaust pipes.
6. Reattach the exhaust heat shield.
7. Lower the vehicle and start the engine to check for leaks.

4. Clear Codes and Test Drive

1. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
2. Conduct a test drive for a minimum of 10-15 minutes, monitoring engine performance and checking for any reoccurrence of the check engine light.