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

Solution

1. Preparation

• Gather tools and parts needed: OBD-II scanner, multimeter, socket set, torque wrench, replacement catalytic converter (if needed), oxygen sensors (if needed), and safety gear.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Remove Old Sensors:
  • Locate the upstream and downstream oxygen sensors.
  • Use a socket wrench to remove the sensors.
• Install New Sensors:
  • Apply anti-seize compound on the threads of the new sensors.
  • Install the new sensors and torque them to manufacturer specifications (typically 30 lb-ft).

3. Inspect and Replace Catalytic Converter (if required)

• Remove Exhaust Components:
  • Unbolt the exhaust pipes connected to the catalytic converter using a socket set.
  • Support the exhaust components to prevent sagging.
• Remove Catalytic Converter:
  • Remove the bolts securing the catalytic converter to the exhaust manifold and the exhaust pipe.
  • Carefully remove the catalytic converter from the vehicle.
• Install New Catalytic Converter:
  • Position the new catalytic converter in place.
  • Bolt it securely to the exhaust manifold and exhaust pipe, ensuring proper alignment.
  • Torque all bolts to manufacturer specifications (usually around 25-30 lb-ft).

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.

5. Test Drive

• Take the vehicle for a test drive to ensure the check engine light does not reappear and monitor performance.