how to fix the P0420 code on my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal.
• Ensure the vehicle is on a flat surface and safely elevated if needed (use jack stands).

2. Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors on the exhaust system.
  2. Disconnect the electrical connectors from both sensors.
  3. Use the O2 sensor socket to unscrew the sensors from the exhaust pipes.
  4. Apply anti-seize compound to the threads of the new sensors.
  5. Install the new sensors and torque to the manufacturer's specifications (typically around 30 ft-lbs).
  6. Reconnect the electrical connectors.

3. Inspect and Clean Catalytic Converter

• Tools Required: Socket set, cleaning solution (if applicable).
• Sub-steps:
  1. Remove the catalytic converter from the exhaust system (may require heating bolts with a torch if rusted).
  2. Inspect for physical damage and excessive carbon build-up.
  3. If cleaning is feasible, use a catalytic converter cleaner according to the manufacturer’s instructions.
  4. Reinstall the catalytic converter, ensuring all gaskets are replaced and bolts are tightened to the specified torque.

4. Clear Codes and Test

• 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 ensure the check engine light does not return.