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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down completely.

2. Inspect and Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter
• Sub-steps:
  1. Using the OBD-II scanner, check the live data for oxygen sensor readings.
  2. Use a multimeter to test the voltage output of the upstream oxygen sensor; it should fluctuate between 0.1V and 0.9V.
  3. Repeat the test for the downstream oxygen sensor; it should remain relatively stable.

3. Replace Faulty Oxygen Sensors (if necessary)

• Tools Required: Socket set, O2 sensor socket
• Sub-steps:
  1. Remove the upstream and/or downstream oxygen sensor using the O2 sensor socket.
  2. Install the new oxygen sensor and ensure it is torqued to the manufacturer’s specifications (usually around 30-40 lb-ft).
  3. Reconnect the electrical connector securely.

4. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Jack and jack stands, socket set, exhaust pipe cutter (if needed)
• Sub-steps:
  1. Raise the vehicle using jack stands for access to the exhaust system.
  2. Inspect the catalytic converter for any signs of damage or blockage.
  3. If replacement is needed, disconnect the exhaust pipes connected to the catalytic converter.
  4. Remove the old catalytic converter and install the new one, ensuring all gaskets are replaced and connections are secure.
  5. Torque the exhaust connections to the specified values.

5. Clear Codes and Test Drive

• Tools Required: OBD-II scanner
• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Start the vehicle and allow it to reach operating temperature.
  4. Take the vehicle for a test drive to verify that the issue has been resolved.