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

Solution

1. Preparation

• Gather tools and parts. Ensure the vehicle is parked on a level surface, and the engine is off and cool.
• Tools required: OBD-II scanner, multimeter, infrared thermometer, socket set, torque wrench, jack stands, safety glasses, gloves.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Sub-steps:
  1. Disconnect the battery to prevent any electrical shorts.
  2. Locate the upstream (pre-catalytic) oxygen sensor and disconnect its electrical connector.
  3. Use a socket wrench to remove the sensor from its mounting.
  4. Install the new oxygen sensor by screwing it into place and tightening to manufacturer's specifications (usually 30 lb-ft).
  5. Reconnect the electrical connector.
  6. Repeat for the downstream (post-catalytic) oxygen sensor if testing indicates it is faulty.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Disconnect the exhaust pipe from the catalytic converter using a socket set.
  3. Remove any heat shields or brackets securing the catalytic converter.
  4. Unbolt the catalytic converter from the exhaust manifold and remove it from the vehicle.
  5. Install the new catalytic converter by reversing the removal steps. Ensure all bolts are tightened to manufacturer specifications.
  6. Reinstall heat shields and reconnect the exhaust pipe.

4. Clear Codes and Test

• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Start the engine and allow it to reach operating temperature.
  4. Take the vehicle for a test drive to ensure no codes return and monitor performance.