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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shock.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, ratchet, and torque wrench
• Steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Remove the electrical connectors from both sensors.
  3. Using the O2 sensor socket, unscrew and remove the faulty sensors.
  4. Install new oxygen sensors in their respective locations and torque to specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack stands, and exhaust hanger removal tool
• Steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Locate the catalytic converter and check for visible damage or blockages.
  3. Remove the exhaust hangers using the exhaust hanger removal tool.
  4. Disconnect the exhaust pipes from the catalytic converter by removing the bolts.
  5. Remove the old catalytic converter and install the new one, ensuring proper alignment.
  6. Reattach the exhaust pipes and torque bolts to specifications (generally around 30-45 lb-ft).
  7. Reinstall the exhaust hangers.

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and take the vehicle for a test drive to monitor performance and ensure the check engine light does not reappear.