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

Solution

1. Preparation

• Gather all necessary tools and parts required for the repair.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors: Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Remove the Oxygen Sensors: Use an oxygen sensor socket or a wrench to carefully unscrew and remove the sensors.
3. Inspect the Sensors: Check for any signs of damage or contamination.
4. Install New Sensors: If necessary, install new oxygen sensors by screwing them in and tightening to the manufacturer’s torque specification (typically around 30 ft-lbs).
5. Reconnect Electrical Connectors: Ensure all connectors are secured and properly connected.

3. Inspect and Replace the Catalytic Converter

1. Examine the Catalytic Converter: Check for any signs of physical damage, such as dents or cracks.
2. Remove the Catalytic Converter: Use a socket set to remove the bolts securing the catalytic converter to the exhaust system.
3. Install New Catalytic Converter: Position the new catalytic converter in place and secure it using the bolts, tightening to the manufacturer’s specifications (usually around 25-30 ft-lbs).
4. Reconnect Exhaust System: Ensure all exhaust connections are secure and free of leaks.

4. Clear Codes and Verify Repair

1. Reconnect the Battery: Once repairs are completed, reconnect the battery.
2. Use OBD-II Scanner: Clear any error codes from the vehicle’s computer.
3. Test Drive: Take the vehicle for a test drive to ensure the check engine light remains off and the vehicle operates normally.