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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is off.
• Disconnect the battery to prevent any electrical issues.

2. Inspect and Replace Faulty O2 Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil
• If oxygen sensors are found to be faulty:
  1. Locate and identify the upstream and downstream O2 sensors.
  2. Apply penetrating oil to the sensor threads to ease removal.
  3. Use the O2 sensor socket to remove the sensor from its connector.
  4. Install the new sensor by threading it into the exhaust pipe. Torque to manufacturer specifications (usually around 30 lb-ft).
  5. Reconnect the sensor plug securely.

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

• Tools Required: Socket set, torque wrench, exhaust gasket, possibly a saw for cutting exhaust pipes
• If the catalytic converter is damaged:
  1. Raise the vehicle securely on jack stands.
  2. Disconnect the exhaust pipes at the flanges leading to the catalytic converter.
  3. Remove any mounting bolts or clamps securing the catalytic converter.
  4. If applicable, cut the exhaust pipes carefully with a saw for easier removal.
  5. Install the new catalytic converter with a new gasket and secure it using bolts. Torque to manufacturer specifications.
  6. Reconnect the exhaust pipes and ensure all connections are tight.

4. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Test drive the vehicle for at least 20-30 minutes, monitoring for any reoccurrence of the check engine light.