how to fix P0420 code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather tools and parts required.
• Disconnect the battery to ensure safety while working on electrical components.
• Allow the engine to cool before proceeding to avoid burns.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:
   • Use an oxygen sensor socket.
   • Disconnect the electrical connector.
2. Install a new upstream oxygen sensor:
   • Apply anti-seize compound on the threads.
   • Torque to manufacturer specifications (typically around 30 lb-ft).
3. Check and replace the downstream oxygen sensor if necessary:
   • Follow the same steps as the upstream sensor.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Remove the exhaust components:
   • Use a socket set to unbolt the catalytic converter from the exhaust manifold and mid-pipe.
   • Carefully lower the catalytic converter from the vehicle.
2. Inspect the catalytic converter:
   • Look for physical damage or excessive carbon buildup.
3. Install a new catalytic converter:
   • Position the new converter and secure it using new gaskets.
   • Torque bolts to manufacturer specifications.
4. Reinstall any removed exhaust components.

4. Clear Codes and Test

1. Reconnect the battery.
2. Use an OBD-II scanner to clear the codes.
3. Start the vehicle and allow it to reach operating temperature.
4. Perform a test drive to ensure the check engine light does not reappear.