how to fix P0420 code on my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery cable.

2. Inspect and Repair Exhaust System

• Tools Required: Socket set, jack stands, exhaust pipe cutter (if needed).
• Inspect the exhaust system for leaks or damage:
  • Use a flashlight to check for cracks or holes.
  • If leaks are found, repair or replace the affected components.
• If the catalytic converter is damaged, proceed to the next step.

3. Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, gasket scraper, new exhaust gaskets.
• Remove the old catalytic converter:
  • Unbolt the catalytic converter from the exhaust manifold and exhaust pipe.
  • Use the gasket scraper to clean the mating surfaces.
• Install the new catalytic converter:
  • Position the new converter in place and secure it with bolts.
  • Torque the bolts to the manufacturer's specifications (usually around 30-40 ft-lbs, but verify with the service manual).

4. Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, torque wrench.
• Remove the upstream and downstream oxygen sensors:
  • Disconnect the electrical connectors.
  • Use the O2 sensor socket to unscrew the sensors.
• Install new oxygen sensors:
  • Thread in the new sensors and torque to manufacturer's specifications (usually around 30 ft-lbs).
  • Reconnect electrical connectors.

5. Reset Check Engine Light

• Reconnect the negative battery cable.
• Use an OBD-II scanner to clear the P0420 code.