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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before starting work.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Instructions:
  1. Locate the upstream and downstream oxygen sensors (before and after the catalytic converter).
  2. Disconnect the electrical connectors from both sensors.
  3. Use the O2 sensor socket to unscrew the sensors from the exhaust system.
  4. Install the new sensors and tighten to manufacturer's specifications (typically around 30 ft-lbs).
  5. Reconnect the electrical connectors.

3. Inspect and Replace the Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool.
• Instructions:
  1. Remove any heat shields or covers obstructing access to the catalytic converter.
  2. Disconnect the exhaust pipes from both ends of the catalytic converter using a socket set.
  3. Remove any mounting bolts or clamps securing the catalytic converter.
  4. Carefully lower the catalytic converter and replace it with a new unit.
  5. Reinstall the exhaust pipes and secure all bolts to the specified torque.
  6. Reattach heat shields or covers.

4. Clear Codes and Recheck System

• Tools Required: OBD-II scanner.
• Instructions:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the system.
  3. Start the engine and allow it to reach operating temperature.