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

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the vehicle battery to ensure safety.
• Allow the exhaust system to cool before inspection.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, multimeter
• Check the upstream oxygen sensor for proper operation and replace if faulty.
  • Disconnect the electrical connector and remove the sensor using the O2 sensor socket.
  • Install the new sensor and torque to manufacturer specifications (typically around 30 lb-ft).
  • Reconnect the electrical connector.
• Repeat the process for the downstream sensor if it is also faulty.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Wrenches, socket set, torque wrench, exhaust sealant
• If the catalytic converter is found to be damaged:
  • Remove the exhaust pipes connected to the catalytic converter by unbolting it from the manifold and the exhaust pipe.
  • Inspect the mounting locations for rust or corrosion and clean if necessary.
  • Install the new catalytic converter, using exhaust sealant on the joints if necessary, and torque to manufacturer specifications.

4. Clear Codes and Test

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Start the vehicle and allow it to reach operating temperature.