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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors on the exhaust system.
  2. Use penetrating oil to loosen the sensors if they are stuck.
  3. Disconnect the electrical connectors from the oxygen sensors.
  4. Remove the sensors using the O2 sensor socket.
  5. Install new oxygen sensors by threading them into place and tightening them to the manufacturer’s specifications (typically around 30-40 ft-lbs).
  6. Reconnect the electrical connectors.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary).
• Sub-steps:
  1. Locate the catalytic converter and check for any visible damage or blockage.
  2. If the catalytic converter is damaged, disconnect the exhaust pipes connected to it.
  3. Remove the old catalytic converter by unbolting it from the exhaust system.
  4. Install the new catalytic converter, ensuring proper alignment with gaskets.
  5. Torque the bolts to the manufacturer’s specifications (usually around 30-40 ft-lbs).

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 engine and allow it to reach normal operating temperature.
  4. Conduct a test drive to ensure the check engine light does not reappear.