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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent any electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors (usually found before and after the catalytic converter).
  2. Disconnect the electrical connectors from both oxygen sensors.
  3. Use a socket wrench to remove the sensors from their respective locations.
  4. Install the new oxygen sensors by hand-tightening and then securing them with a torque wrench to the manufacturer-recommended torque specification (usually around 30-40 ft-lbs).
  5. Reconnect the electrical connectors ensuring they click into place.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. Locate the catalytic converter and inspect for any physical damage or clogs.
  2. If replacement is necessary, remove the exhaust bolts using a socket set, and detach the catalytic converter from the exhaust system.
  3. Install the new catalytic converter, ensuring a proper fit with the exhaust pipe.
  4. Secure with new gaskets and bolts, tightening them to the specified torque (usually around 20-30 ft-lbs).
  5. Reconnect any O2 sensors previously removed.

4. Reset the Check Engine Light

• Sub-steps:
  1. Reconnect the battery terminals securely.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Start the engine and allow it to reach operating temperature.