how to troubleshoot P0420 code in my Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather all tools and parts required for the repair.
• Ensure the vehicle is parked on a level surface and the engine is off.
• Disconnect the battery to prevent any electrical issues during repair.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  • Locate the upstream and downstream oxygen sensors on the exhaust system.
  • Use a socket wrench to remove the oxygen sensors.
  • Inspect the sensors for carbon buildup or damage.
  • If faulty, replace with new sensors. Ensure they are the correct OEM parts.
  • Torque the sensors to the manufacturer's specifications (usually around 30 ft-lbs).

3. Inspect and Replace Catalytic Converter

• Sub-steps:
  • Inspect the catalytic converter for dents, holes, or signs of overheating.
  • Remove the exhaust clamps and bolts securing the catalytic converter.
  • Carefully lower the catalytic converter from the exhaust system.
  • Install the new catalytic converter, ensuring proper alignment.
  • Reattach all clamps and bolts, torquing them to the manufacturer's specifications.

4. Clear Codes and Reconnect Battery

• Sub-steps:
  • Use the OBD-II scanner to clear the P0420 code.
  • Reconnect the battery terminals securely.

5. Conduct a Test Drive

• Sub-steps:
  • Start the vehicle and allow it to idle for a few minutes.
  • Take the vehicle for a test drive to ensure the check engine light does not reappear and performance is restored.