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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to avoid electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Unplug the electrical connectors from both O2 sensors.
  3. Use the O2 sensor socket to remove the upstream sensor first.
  4. Install the new upstream O2 sensor and torque it to manufacturer specifications (typically around 30 lb-ft).
  5. Repeat the removal and installation process for the downstream O2 sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if needed), gasket scraper
• Sub-steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Remove any heat shields obstructing access to the catalytic converter.
  3. Disconnect the exhaust pipes from the catalytic converter using a socket set. Cut the pipes if necessary.
  4. Remove the old catalytic converter and clean the mating surfaces.
  5. Install the new catalytic converter, ensuring proper alignment with the exhaust system.
  6. Reattach any heat shields and exhaust pipes, tightening all bolts to the specified torque.

4. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer system.