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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the vehicle battery to ensure safety while working on the electrical components.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, torque wrench, penetrating oil.
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Apply penetrating oil to the sensor threads.
  2. Use the O2 sensor socket to unscrew the sensor.
  3. Disconnect the electrical connector.
• Install the new upstream oxygen sensor:
  1. Apply anti-seize compound to the threads of the new sensor.
  2. Install and torque to the manufacturer’s specifications (typically around 30-40 ft-lbs).
  3. Reconnect the electrical connector.
• Repeat the process for the downstream (post-catalytic) oxygen sensor if needed.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, exhaust pipe cutter (if needed), gasket scraper, torque wrench.
• Remove the catalytic converter:
  1. Identify the mounting bolts and any clamps securing the catalytic converter.
  2. Use a socket set to remove the bolts/clamps and disconnect the exhaust sections.
  3. If the converter is difficult to remove, carefully cut the exhaust pipe using an exhaust pipe cutter.
• Install the new catalytic converter:
  1. Clean the mating surfaces on the exhaust pipes to ensure a good seal.
  2. Position the new catalytic converter and secure it with bolts/clamps, torquing to specifications.
  3. Reconnect the exhaust system.

4. Clear Codes and Test Drive

• Reconnect the vehicle battery.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and let it warm up.
• Test drive the vehicle under various conditions to ensure the code does not reappear.