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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is on a level surface and securely lifted using jack stands.
• Disconnect the vehicle battery to prevent any electrical issues during repairs.

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 unscrew the old oxygen sensors from their respective positions.
   • Tools Required: Oxygen sensor socket, wrench
3. Install the new oxygen sensors, ensuring they are tightened to the manufacturer's specifications (typically 30 Nm).
4. Reconnect the electrical connectors to the new sensors.

3. Inspect and Replace Catalytic Converter (if necessary)

1. If oxygen sensors are functioning properly, inspect the catalytic converter for blockage or damage.
2. Remove the exhaust pipes connected to the catalytic converter using a socket set.
   • Tools Required: Socket set, penetrating oil (if bolts are rusted)
3. Remove the old catalytic converter from the vehicle.
4. Install the new catalytic converter, ensuring that all bolts are tightened to the manufacturer's torque specifications.
5. Reattach the exhaust pipes securely.

4. Clear Error Codes

1. Reconnect the battery.
2. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
3. Start the engine and let it idle for a few minutes to ensure all systems reset.