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

Solution

1. Preparation

• Gather tools and parts required for repair.
• Safety first: disconnect the battery to prevent electrical issues.
• Ensure vehicle is on a level surface and use jack stands if needed.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, and torque wrench.
• Remove the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors:
  1. Locate the sensors on the exhaust manifold and catalytic converter.
  2. Use the O2 sensor socket to unscrew the sensors.
• Install new oxygen sensors:
  1. Apply anti-seize compound on the threads of the new sensors.
  2. Torque to manufacturer specifications (typically around 30-40 lb-ft).

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, cutting torch or exhaust pipe cutter (if necessary).
• Check the catalytic converter for physical damage or excessive carbon buildup:
  1. Remove the exhaust pipes leading to the catalytic converter.
  2. Inspect the inside of the converter for blockages.
• If faulty, replace the catalytic converter:
  1. Disconnect any mounting hardware and sensors attached to the catalytic converter.
  2. Remove the old catalytic converter.
  3. Install the new catalytic converter, ensuring proper alignment and sealing.
  4. Torque all connections to manufacturer specifications.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals securely.
• Use the OBD-II scanner to clear the error codes from the ECU.