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

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool completely.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench
• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Using the O2 sensor socket, carefully unscrew the upstream sensor.
  3. Install the new oxygen sensor, ensuring it is tightened to the manufacturer’s torque specification (typically around 30 ft-lbs).
  4. Repeat for the downstream oxygen sensor if necessary.

3. Inspect Catalytic Converter

• Tools Required: Jack and jack stands, exhaust pipe cutter (if necessary), wrench set
• Sub-steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Visually inspect the catalytic converter for any signs of physical damage or blockage.
  3. If damaged, use an exhaust pipe cutter to carefully remove the old catalytic converter from the exhaust system.
  4. Install the new catalytic converter, ensuring proper alignment and secure all connections.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner
• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the engine control module.
  3. Start the engine and allow it to reach operating temperature.
  4. Perform a test drive to ensure the vehicle operates normally and monitor for any check engine light reactivation.