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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the vehicle to cool down before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  • Locate the upstream and downstream oxygen sensors.
  • Use an O2 sensor socket to remove the upstream sensor (pre-catalytic converter).
  • Inspect the sensor for signs of contaminants or damage; replace if necessary.
  • Install the new sensor, ensuring it is torqued to the manufacturer's specifications (typically around 30 lb-ft).
  • Repeat for the downstream sensor if it shows abnormal readings.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  • Remove the exhaust pipe connected to the catalytic converter using a socket set.
  • Inspect the catalytic converter for any signs of damage or clogging (e.g., rattling sound, discoloration).
  • If defective, unbolt the catalytic converter and remove it.
  • Install a new catalytic converter, ensuring that gaskets are replaced and connections are secure.
  • Torque all bolts to the specified values (often around 25 lb-ft).

4. Clear Codes and Test Drive

• Sub-steps:
  • Reconnect the negative battery terminal.
  • Use the OBD-II scanner to clear the P0420 code.
  • Start the engine and allow it to reach operating temperature.
  • Take the vehicle for a test drive to ensure the check engine light does not reappear.