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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is on a level surface and securely lifted.
• Disconnect the battery to avoid electrical shorts.

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 on the exhaust manifold.
  2. Use the O2 sensor socket to unscrew the sensor.
  3. Install the new upstream O2 sensor and torque to manufacturer specifications (typically around 30 ft-lbs).
• Repeat for the downstream oxygen sensor, which is located after the catalytic converter.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Wrench set, socket set, exhaust pipe cutter or saw, gasket scraper.
• Remove the old catalytic converter:
  1. Disconnect the exhaust pipe from the catalytic converter using the appropriate size wrench.
  2. Remove any mounting bolts or clamps securing the catalytic converter to the exhaust system.
  3. Carefully cut or unbolt the converter from the exhaust.
• Install the new catalytic converter:
  1. Position the new catalytic converter and secure it with the bolts or clamps.
  2. Make sure to replace or install new gaskets if necessary.
  3. Torque bolts to the manufacturer specification.

4. Reconnect Battery and Clear Codes

• Reconnect the battery.
• Use an OBD-II scanner to clear the fault codes.
• Start the engine and allow it to reach operating temperature.