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

Solution

1. Preparation

• Gather tools and parts required.
• Park the vehicle on a level surface and engage the parking brake.
• Disconnect the battery to avoid electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench, multimeter.
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Use the O2 sensor socket to remove the sensors from the exhaust manifold and exhaust pipe.
  4. Install new oxygen sensors, ensuring they are torqued to manufacturer specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connectors.

3. Check and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack stands, exhaust hanger removal tool.
• Parts Required: New catalytic converter (if required).
• Sub-steps:
  1. Raise the vehicle and secure it with jack stands.
  2. Remove any exhaust hangers using the exhaust hanger removal tool.
  3. Disconnect any flanges or bolts attaching the catalytic converter to the exhaust system.
  4. Remove the old catalytic converter.
  5. Install the new catalytic converter, ensuring all bolts are tightened to manufacturer specifications (typically around 25 lb-ft).
  6. Reinstall exhaust hangers and lower the vehicle.

4. Reset the PCM

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the Powertrain Control Module (PCM).
  3. Take the vehicle for a test drive to allow the PCM to re-evaluate the catalytic converter's efficiency.