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

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

1. Locate the Sensors:
   • Find the upstream and downstream oxygen sensors on the exhaust manifold and catalytic converter.
2. Remove Sensors:
   • Use a socket wrench to carefully unscrew the sensors.
   • Disconnect the electrical connectors.
3. Install New Sensors:
   • Apply anti-seize compound on the threads of the new oxygen sensors.
   • Install the new sensors by hand, then tighten to manufacturer specifications (usually around 30 lb-ft).
4. Reconnect Electrical Connectors:
   • Ensure connectors are firmly attached to the new sensors.

3. Inspect and Replace Catalytic Converter

1. Remove Exhaust Components:
   • Unbolt any exhaust hangers or brackets securing the catalytic converter.
   • Use a socket set to remove bolts connecting the catalytic converter to the exhaust system.
2. Install New Catalytic Converter:
   • Position the new catalytic converter in place.
   • Reattach all bolts and hangers, tightening to the manufacturer’s torque specifications (typically around 30-40 lb-ft).
3. Recheck for Exhaust Leaks:
   • Start the engine and listen for any leaks around the exhaust joints.

4. Clear Codes and Test Drive

1. Reconnect Battery:
   • Reattach the battery terminals securely.
2. Clear Codes:
   • Use the OBD-II scanner to erase the P0420 code.
3. Test Drive:
   • Drive the vehicle for a short distance to monitor performance and ensure the check engine light does not reappear.