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

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 for safety.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Remove the upstream oxygen sensor:
  1. Locate the upstream O2 sensor (usually near the exhaust manifold).
  2. Disconnect the electrical connector.
  3. Use the O2 sensor socket to remove the sensor.
• Install the new upstream O2 sensor:
  1. Apply anti-seize compound to the threads of the new sensor.
  2. Install and torque the sensor to the manufacturer's specification (typically around 30 ft-lbs).
  3. Reconnect the electrical connector.
• Repeat the process for the downstream oxygen sensor.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torch wrench, exhaust pipe cutter (if necessary)
• Remove the old catalytic converter:
  1. Locate the catalytic converter in the exhaust system.
  2. Disconnect any brackets or heat shields holding it in place.
  3. Use an exhaust pipe cutter to remove any welded connections if applicable.
  4. Carefully remove the catalytic converter from the exhaust system.
• Install the new catalytic converter:
  1. Place the new catalytic converter into position.
  2. Secure with any necessary brackets and gaskets.
  3. Reconnect exhaust pipes and torque connections to specification.

4. Clear Codes and Test Drive

• Use the OBD-II scanner to clear the P0420 code.
• Reconnect the negative battery terminal.
• Start the engine and take the vehicle for a test drive to ensure that the check engine light does not reappear.