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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is in a safe, well-ventilated area.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors (if needed)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
  • 1. Locate the pre-catalytic and post-catalytic oxygen sensors on the exhaust system.
  • 1. Disconnect the electrical connectors from each sensor.
  • 1. Using the O2 sensor socket, unscrew and remove the sensors.
  • 1. Install new oxygen sensors and torque to the manufacturer’s specifications (usually around 30 ft-lbs).
  • 1. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary).
  • 1. Locate the catalytic converter in the exhaust system.
  • 1. Remove the exhaust clamps and any bolts securing the catalytic converter to the exhaust system.
  • 1. If necessary, cut the exhaust pipe to remove the old catalytic converter.
  • 1. Install the new catalytic converter, ensuring proper alignment.
  • 1. Secure the converter with exhaust clamps or bolts, torquing to manufacturer specifications (typically around 25 ft-lbs).

4. Clear Error Codes and Test

• Tools Required: OBD-II scanner.
  • 1. Reconnect the negative battery terminal.
  • 1. Use the OBD-II scanner to clear the P0420 code.
  • 1. Start the engine and let it idle for a few minutes.
  • 1. Take the vehicle for a test drive to ensure that the check engine light does not reappear.