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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to prevent electrical issues.
• Allow the engine to cool down before starting work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Remove the rear oxygen sensor (downstream) from the exhaust pipe using the O2 sensor socket.
  2. Install the new oxygen sensor and torque it to manufacturer's specifications (typically 30 ft-lbs).
  3. Repeat the process for the front oxygen sensor if needed.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary).
• Sub-steps:
  1. Disconnect the exhaust system from the catalytic converter by removing the bolts and clamps.
  2. Remove the catalytic converter from its mounting points.
  3. Install the new catalytic converter, ensuring proper alignment.
  4. Reconnect the exhaust system and torque all bolts to the manufacturer's specifications (typically 30-40 ft-lbs).

4. Clear Codes and Test

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
  3. Start the engine and allow it to reach operating temperature.

5. Road Test

• Sub-steps:
  1. Take the vehicle for a test drive to ensure the check engine light does not return and performance is restored.