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

Solution

1. Preparation

• Gather necessary tools and safety equipment.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the vehicle to cool down before starting.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Use the O2 sensor socket to remove the upstream oxygen sensor.
  3. Inspect the sensor for contamination and perform a continuity test; replace if faulty.
  4. Repeat the process for the downstream oxygen sensor.
  5. Install new sensors and torque them to manufacturer specifications (usually around 30 lb-ft).

3. Inspect and Clean Catalytic Converter

• Tools Required: Torque wrench, penetrating oil, cleaning brush (if needed).
• Sub-steps:
  1. Inspect the catalytic converter for dents, holes, or any signs of blockage.
  2. If the converter is externally damaged, it may need replacement.
  3. For internal cleaning, use a catalytic converter cleaner according to the product instructions.
  4. If cleaning is not effective, proceed to replace the catalytic converter.

4. Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust gasket.
• Sub-steps:
  1. Disconnect the exhaust pipes from the catalytic converter using a socket set.
  2. Remove any mounting brackets or hangers securing the converter.
  3. Install the new catalytic converter, ensuring proper alignment with exhaust pipes.
  4. Use a new exhaust gasket and torque bolts to manufacturer specifications.

5. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code and any other stored codes.