how to fix P0420 code in Toyota Highlander Fourth Generation (2020-present)

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 terminal of the battery to prevent 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. Disconnect the electrical connectors from both oxygen sensors.
  3. Using the O2 sensor socket, remove the upstream sensor and inspect it for carbon buildup or damage.
  4. Install the new upstream oxygen sensor, torque it to manufacturer specifications (usually around 33 ft-lbs).
  5. Repeat the process for the downstream oxygen sensor if necessary.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter, gasket scraper, torque wrench
• Sub-steps:
  1. Raise the vehicle using a jack and secure with jack stands.
  2. Locate the catalytic converter and inspect it for physical damage.
  3. If replacement is necessary, use an exhaust pipe cutter to remove the old catalytic converter from the exhaust system.
  4. Clean the mating surfaces on the exhaust pipes to ensure a good seal.
  5. Install the new catalytic converter, ensuring all bolts are tightened to the specified torque (usually around 30-40 ft-lbs).
  6. Reconnect any exhaust hangers and inspect for proper alignment.

4. Reconnect Battery and Clear Codes

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