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

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter
• If the upstream or downstream oxygen sensor is faulty, replace it:
  1. Locate the oxygen sensors (upstream before the catalytic converter, downstream after).
  2. Use the O2 sensor socket to unscrew the defective sensor.
  3. Apply anti-seize compound on the threads of the new sensor.
  4. Install the new sensor and torque it to the manufacturer's specifications (approximately 30 ft-lbs).
  5. Reconnect the electrical connector.

3. Inspect and Repair Exhaust System

• Tools Required: Socket set, exhaust pipe cutter (if necessary)
• Check for leaks or damage in the exhaust system:
  1. Visually inspect the catalytic converter and exhaust pipes for cracks or holes.
  2. Repair any leaks found using exhaust repair tape or replace damaged sections as needed.
  3. Ensure all connections are tight and secure.

4. Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust gasket
• If the catalytic converter is determined to be faulty:
  1. Remove the exhaust pipes connected to the catalytic converter using the socket set.
  2. Unbolt the catalytic converter from the exhaust system.
  3. Install the new catalytic converter, ensuring proper orientation.
  4. Torque all bolts to the manufacturer’s specifications (typically around 30-40 ft-lbs).
  5. Replace any gaskets as necessary.

5. Reset the Engine Control Module (ECM)

• Tools Required: OBD-II scanner
• After repairs:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the ECM.