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

Solution

1. Preparation

• Gather tools and parts.
• Ensure the vehicle is on a level surface and secure it with wheel chocks and jack stands.
• Disconnect the negative battery terminal to prevent electrical issues.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench
• Check the operation of the upstream and downstream oxygen sensors.
• If faulty, replace the sensors:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Using the O2 sensor socket, carefully remove the faulty sensor.
  3. Install the new sensor and torque to the manufacturer’s specifications (typically around 30 ft-lbs).

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, exhaust pipe cutter, gasket scraper
• If the catalytic converter is determined to be faulty:
  1. Use an exhaust pipe cutter to remove the old catalytic converter from the exhaust system.
  2. Clean the mating surfaces of the exhaust pipes to ensure a good seal.
  3. Install the new catalytic converter and secure it with the appropriate clamps and bolts; torque to specifications.

4. Clear Error Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the ECM.

5. Final Checks

• Start the vehicle and allow it to reach operating temperature.
• Check for exhaust leaks and ensure there are no new codes.