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

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, socket set, torque wrench, exhaust pipe cutter (if needed), and safety glasses.
• Ensure the vehicle is parked on a flat surface and the parking brake is engaged.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Disconnect the negative battery terminal.
  2. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  3. Remove the electrical connectors from both sensors.
  4. Use a socket wrench to unscrew the sensors and remove them from the exhaust manifold and catalytic converter.
  5. Install new oxygen sensors in reverse order, ensuring they are tightened to the manufacturer's specifications (check service manual for torque values).
  6. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. If the catalytic converter is damaged or clogged, cut the exhaust pipe using an exhaust pipe cutter.
  2. Remove the mounting bolts holding the catalytic converter in place.
  3. Install the new catalytic converter, ensuring proper alignment with the exhaust system.
  4. Secure it with bolts and torque them to the manufacturer's specifications.
  5. If applicable, use new gaskets to prevent exhaust leaks.

4. Clear Error Codes

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the system.
  3. Start the engine and verify that the check engine light does not reappear.