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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to avoid any electrical mishaps.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, and extension.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors. The upstream sensor is typically located before the catalytic converter, and the downstream sensor is located after it.
  2. Remove the electrical connector from each sensor.
  3. Use the O2 sensor socket to carefully unscrew the sensors from their respective locations.
  4. Install the new oxygen sensors, ensuring they are tightened to the manufacturer's specifications (usually around 30 lb-ft).
  5. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, and exhaust gasket (if necessary).
• Sub-steps:
  1. Locate the catalytic converter in the exhaust system.
  2. Remove any heat shields, if present, to access the catalytic converter.
  3. Use a socket set to unbolt the catalytic converter from the exhaust manifold and the exhaust pipe.
  4. Inspect the flanges and gaskets; replace if damaged.
  5. Install the new catalytic converter, ensuring it is aligned properly and securely bolted (torque to manufacturer's specifications).
  6. Reattach any heat shields and ensure all connections are tight.

4. Reset the ECU

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear any trouble codes from the ECU.
  3. Perform a test drive to ensure that the check engine light does not return.