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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the vehicle battery to ensure safety while working on electrical components.
• Allow the vehicle to cool down if it has been running.

2. Inspect and Replace Oxygen Sensors (if needed)

• Tools Required: O2 sensor socket, wrench set, torque wrench
• Remove the upstream (pre-catalytic) oxygen sensor using an O2 sensor socket.
  • Sub-steps:
    • Locate the sensor on the exhaust manifold or pipe before the catalytic converter.
    • Disconnect the electrical connector.
    • Use the O2 sensor socket and wrench to unscrew the sensor.
• Install the new sensor, ensuring it is properly torqued to manufacturer specifications (usually around 30-40 Nm).
• Reconnect the electrical connector.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if needed), gasket scraper
• Raise the vehicle using a jack and secure it with jack stands.
• Inspect the catalytic converter for physical damage or blockage.
  • Sub-steps:
    • Look for signs of rattling, dents, or exhaust leaks.
    • Use an infrared thermometer to measure inlet and outlet temperatures.
• If replacement is necessary, disconnect the exhaust pipes from the catalytic converter using a socket set.
• Remove the old catalytic converter and clean the mounting surfaces.
• Install the new catalytic converter, ensuring proper alignment and sealing.
• Tighten all bolts to manufacturer torque specifications.

4. Clear Error Codes and Test Drive

• Reconnect the vehicle battery.
• Use an OBD-II scanner to clear the P0420 code.
• Start the engine and let it run for a few minutes.
• Test drive the vehicle under various conditions to ensure the code does not return.