how to troubleshoot my Toyota Highlander Third Generation (2014-2019) with P0420 code?

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent any electrical shorts during repairs.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Locate the upstream (before the catalytic converter) and downstream (after the catalytic converter) oxygen sensors.
  2. Use the O2 sensor socket to remove both sensors by turning counterclockwise.
  3. Inspect the wiring and connectors for damage; replace any damaged components.
  4. Install the new oxygen sensors by threading them into the exhaust pipe and tightening them to the manufacturer's specified torque (typically around 30 lb-ft).
  5. Reconnect the electrical connectors.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust gasket.
• Sub-steps:
  1. Raise the vehicle and secure it with jack stands.
  2. Locate the catalytic converter along the exhaust system.
  3. Unbolt the catalytic converter from the exhaust pipe using the socket set.
  4. Inspect the old catalytic converter for signs of damage or clogging; if damaged, proceed to replace it.
  5. Install the new catalytic converter, ensuring to use a new exhaust gasket.
  6. Tighten the bolts to the manufacturer’s specified torque settings.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the vehicle’s battery.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
  3. Start the engine and let it idle for a few minutes.
  4. Conduct a test drive under varied conditions to ensure the code does not reappear.