how to fix P0420 code on Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, jack and jack stands
• Gather necessary parts for replacement if required (see Parts Required below).
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors in the exhaust system.
  2. Remove the electrical connector from each oxygen sensor.
  3. Use a socket wrench to unscrew and remove the sensors from their respective locations.
  4. Install new oxygen sensors by screwing them into place and reconnecting the electrical connectors.
  5. Torque the sensors to the manufacturer's specifications (typically around 30-40 lb-ft).

3. Inspect and Replace the Catalytic Converter

• Sub-steps:
  1. Safely lift the vehicle using a jack and secure it with jack stands.
  2. Remove the bolts securing the catalytic converter to the exhaust manifold and the exhaust pipe using a socket set.
  3. Carefully detach the catalytic converter from the exhaust system.
  4. Install the new catalytic converter and secure it using the bolts removed earlier.
  5. Torque the bolts to the manufacturer's specifications (check service manual for exact values).

4. Clear Codes and Test

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