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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, ratchet, torque wrench, anti-seize compound.
• Steps:
  1. Locate the upstream and downstream oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Use the O2 sensor socket to remove the sensors from the exhaust manifold and catalytic converter.
  4. Apply a small amount of anti-seize compound to the threads of the new sensors.
  5. Install the new sensors and torque to manufacturer specifications (typically around 30 lb-ft).
  6. Reconnect the electrical connectors.

3. Inspect and Replace the Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed), gaskets, sealing compound.
• Steps:
  1. Remove any heat shields covering the catalytic converter.
  2. Use a socket set to remove the bolts securing the catalytic converter to the exhaust system.
  3. If necessary, cut the exhaust pipe to remove the catalytic converter.
  4. Install the new catalytic converter, ensuring proper alignment with exhaust pipes.
  5. Torque all bolts to manufacturer specifications (typically around 30 lb-ft).
  6. Replace any gaskets or use sealing compound as required.

4. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the trouble codes.