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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the vehicle to cool down before starting work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: Oxygen sensor socket, torque wrench
• Remove the upstream oxygen sensor from the exhaust manifold.
  • Ensure the engine is cool to avoid burns.
  • Use the oxygen sensor socket to unscrew the sensor.
• Install the new upstream oxygen sensor and torque to manufacturer specifications (typically around 30 ft-lbs).
• Repeat the process for the downstream oxygen sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, jack stands
• Raise the vehicle securely using jack stands.
• Remove any heat shields covering the catalytic converter.
• Unbolt the catalytic converter from the exhaust system.
  • Pay attention to gasket condition; replace if worn.
• Install the new catalytic converter and torque bolts to manufacturer specifications.
• Reinstall heat shields if removed.

4. Clear Code and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Test drive the vehicle under various conditions to ensure the issue is resolved.