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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and securely raise it with jack stands.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Instructions:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Disconnect the electrical connector from each sensor.
  3. Use the O2 sensor socket to remove the sensors.
  4. Install new sensors by threading them into the exhaust system and tightening them to the manufacturer’s specified torque (typically around 30-40 lb-ft).
  5. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, cutting tool (if necessary), gasket scraper, torque wrench.
• Instructions:
  1. Remove any heat shields covering the catalytic converter.
  2. Disconnect the exhaust piping from the catalytic converter; use a cutting tool if necessary.
  3. Remove the old catalytic converter by unbolting it from the exhaust manifold and exhaust pipe.
  4. Clean any gasket material from the mating surfaces on the exhaust manifold and pipe.
  5. Install the new catalytic converter with new gaskets, making sure to align it properly.
  6. Bolt everything back in place, tightening to the manufacturer's specified torque.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.