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

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. Using a wrench, carefully remove the sensors from their respective locations.
3. Inspect the wiring and connectors for damage; replace any damaged parts.
4. Install new oxygen sensors, tightening them to the manufacturer’s specifications (typically around 30 ft-lbs).
5. Reconnect the battery.

3. Inspect and Replace Catalytic Converter

1. Raise the vehicle securely on jack stands.
2. Remove any heat shields or protective covers obstructing access to the catalytic converter.
3. Unbolt the catalytic converter from the exhaust system using a socket set.
4. Inspect the old catalytic converter for signs of damage or clogging; if it appears compromised, replace it.
5. Install the new catalytic converter, ensuring proper alignment and sealing with gaskets as needed.
6. Torque the bolts to the manufacturer’s specifications.

4. Clear Codes and Test Drive

1. Reconnect the OBD-II scanner to clear the P0420 code from the system.
2. Start the engine and allow it to reach operating temperature.
3. Perform a test drive under various conditions (city and highway) to ensure the issue is resolved.