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

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Sub-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 upstream sensor first, then the downstream sensor.
  4. Install the new sensors in reverse order, ensuring they are torqued to manufacturer specifications (typically around 30 ft-lbs).

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

• Tools Required: Socket set, jack stands, exhaust pipe cutter (if applicable), gasket scraper
• Sub-steps:
  1. Raise the vehicle using jack stands and secure it.
  2. Remove the bolts securing the catalytic converter to the exhaust manifold and the exhaust pipe.
  3. Carefully remove the catalytic converter, taking care not to damage surrounding components.
  4. Clean the mating surfaces with a gasket scraper to ensure a proper seal.
  5. Install the new catalytic converter, securing it with new gaskets and bolts, torquing to the specified values (typically around 30 ft-lbs).

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner
• Sub-steps:
  1. Reconnect the vehicle battery.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Start the engine and let it idle for a few minutes.
  4. Take the vehicle for a test drive to ensure the check engine light does not reappear.