how to fix P0420 code on my 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 battery to prevent any electrical issues.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Use a socket wrench to remove the oxygen sensors from their respective locations.
3. Inspect the sensors for damage; replace if necessary.
4. Install new sensors by screwing them into place and tightening them to the manufacturer's specifications (usually around 30 ft-lbs).
5. Reconnect the battery.

3. Inspect and Replace the Catalytic Converter

1. If the oxygen sensors are functioning correctly but the P0420 code persists, inspect the catalytic converter.
2. Remove the exhaust components that are obstructing access to the catalytic converter (may require a socket set and penetrating oil).
3. Unbolt the catalytic converter from the exhaust system.
4. Install the new catalytic converter, ensuring proper alignment and sealing.
5. Torque the bolts to the specified torque values (typically around 30-35 ft-lbs).
6. Reassemble any removed exhaust components.

4. Clear Codes and Test Drive

1. Use the OBD-II scanner to clear the P0420 code from the system.
2. Start the vehicle and allow it to reach operating temperature.
3. Perform a test drive to ensure the check engine light does not reappear.