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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the vehicle's battery to prevent electrical shorts.
• Allow the engine to cool down completely.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, multimeter
• Steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Use the O2 sensor socket to remove the upstream sensor first.
  3. Inspect the threads for damage; if they are damaged, replace the sensor.
  4. Install the new upstream sensor and torque it to the manufacturer's specification (usually around 30 ft-lbs).
  5. Repeat the process for the downstream oxygen sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust gasket
• Steps:
  1. Remove the bolts securing the catalytic converter to the exhaust system using a socket set.
  2. Carefully detach the catalytic converter from the exhaust pipes.
  3. Inspect the old catalytic converter for any signs of damage or clogging.
  4. If replacement is needed, install the new catalytic converter with a new gasket.
  5. Torque the bolts to the manufacturer's specifications to ensure a tight fit.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner
• Steps:
  1. Reconnect the vehicle's battery.
  2. Use the OBD-II scanner to clear the P0420 code from the system.
  3. Start the engine and allow it to reach operating temperature.
  4. Take the vehicle for a test drive to ensure the check engine light does not reappear.