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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to avoid electrical issues during repairs.
• Allow the engine to cool before working on exhaust components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil.
• Remove the pre-catalytic and post-catalytic oxygen sensors using an O2 sensor socket.
  • If the sensors are stuck, apply penetrating oil and allow it to soak in before attempting removal.
• Install new oxygen sensors with the proper torque specification (typically around 30 ft-lbs).
• Reconnect the wiring harness to the new sensors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack stands, exhaust pipe cutter (if needed), gasket scraper.
• Raise the vehicle securely on jack stands.
• Remove any heat shields if present.
• Disconnect the exhaust pipes from the catalytic converter using a socket set or exhaust cutter if necessary.
• Inspect the catalytic converter for physical damage or excessive soot buildup.
• If the catalytic converter is determined to be faulty, replace it with a new unit. Make sure to use an OEM or high-quality aftermarket part.
• Ensure all gaskets are replaced and seal properly during reinstallation.

4. Clear the Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.