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

Solution

1. Preparation

• Gather required tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the vehicle to cool down before starting work on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, and torque wrench.
• Procedure:
  1. Identify and locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Use the O2 sensor socket to unscrew the sensors from the exhaust manifold and catalytic converter.
  4. Install the new oxygen sensors, ensuring they are tightened to the manufacturer’s torque specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack and jack stands, exhaust hanger removal tool, and sealing gasket.
• Procedure:
  1. Raise the vehicle securely using jack stands.
  2. Locate the catalytic converter in the exhaust system.
  3. Remove any exhaust hangers or brackets holding the catalytic converter in place.
  4. Unscrew the bolts securing the catalytic converter to the exhaust manifold and the exhaust pipe.
  5. Carefully remove the catalytic converter and inspect for damage or blockage.
  6. If replacement is needed, install the new catalytic converter and ensure it is aligned properly with exhaust flanges.
  7. Reattach all hangers and brackets. Use new gaskets to prevent leaks.

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0420 code from the vehicle’s computer.
• Test drive the vehicle to ensure that the check engine light does not reappear.