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

Solution

1. Preparation

• Gather tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shocks.

2. Replace Faulty Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Remove the upstream (pre-catalytic) oxygen sensor from the exhaust manifold.
  • Use the O2 sensor socket to unscrew the sensor.
  • Disconnect the electrical connector from the sensor.
• Install the new upstream sensor.
  • Apply anti-seize lubricant to the threads of the new sensor.
  • Hand-tighten the sensor, then torque it to the manufacturer’s specification (typically around 30 ft-lbs).
  • Reconnect the electrical connector.
• Repeat the process for the downstream (post-catalytic) oxygen sensor if it is faulty.

3. Replace the Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter, new gaskets, clamps
• Disconnect the exhaust pipes from the catalytic converter.
  • Use the exhaust pipe cutter if necessary to remove the old converter.
• Install the new catalytic converter.
  • Ensure new gaskets are installed to prevent leaks.
  • Secure the converter to the exhaust system with appropriate clamps and torque to manufacturer specifications.
• Reconnect any heat shields or brackets removed during the process.

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Start the vehicle and perform a test drive to allow the ECU to monitor the system.