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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench, penetrating oil (if needed)
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Use penetrating oil on the sensor threads if they are rusted or stuck. Allow it to sit for a few minutes.
  3. Disconnect the electrical connectors from both oxygen sensors.
  4. Use an O2 sensor socket to remove both sensors.
  5. Install new sensors in the reverse order. Torque them to the manufacturer’s specifications (typically around 30 lb-ft).

3. Inspect and Replace the Catalytic Converter (if necessary)

• Tools Required: Socket set, cutting tool (if welded), welding equipment (if needed), jack stands
• Sub-steps:
  1. Lift the vehicle securely using jack stands.
  2. Inspect the catalytic converter for any physical damage or blockage.
  3. If damaged, remove any bolts or clamps securing the catalytic converter to the exhaust system.
  4. For welded units, use a cutting tool to remove the old converter.
  5. Install the new catalytic converter, ensuring all connections are secure. Torque bolts to manufacturer specifications.
  6. Reconnect any electrical connectors that were disconnected during the process.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner
• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the system.
  3. Start the engine and allow it to reach operating temperature.
  4. Take the vehicle for a test drive to ensure the engine runs smoothly and monitor for return of the check engine light.