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

Solution

1. Preparation

• Gather tools and parts.
• Ensure the vehicle is parked on a level surface and the parking brake is engaged.
• Disconnect the negative battery terminal to prevent electrical issues.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet and extensions, torque wrench, penetrating oil.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors on the exhaust system.
  2. Apply penetrating oil to the sensor threads and wait a few minutes.
  3. Disconnect the electrical connectors from each oxygen sensor.
  4. Remove the sensors using the O2 sensor socket and ratchet.
  5. Install new oxygen sensors and torque to manufacturer's specifications (typically around 30 ft-lbs).
  6. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust pipe cutter or saw, gaskets.
• Sub-steps:
  1. Remove any heat shields or covers that may obstruct access to the catalytic converter.
  2. Use an exhaust pipe cutter or saw to cut out the old catalytic converter from the exhaust system.
  3. Inspect the mounting points and ensure no debris is present.
  4. Install the new catalytic converter, ensuring proper alignment with exhaust pipes.
  5. Use new gaskets and torque bolts to manufacturer's specifications.
  6. Reinstall any removed heat shields or covers.

4. Reset Engine Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear any stored fault codes from the vehicle's computer.