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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, backpressure gauge.
• Ensure the vehicle is parked on a level surface and the engine is off. Disconnect the battery to prevent any electrical shorts.

2. Replace Oxygen Sensors

1. Remove Negative Terminal: Disconnect the negative battery terminal to ensure safety.
2. Locate Oxygen Sensors: Identify the upstream and downstream oxygen sensors connected to the exhaust system.
3. Unplug Sensors: Carefully unplug the electrical connectors from both sensors.
4. Remove Sensors: Use a socket wrench to remove the oxygen sensors from their respective locations.
5. Install New Sensors: Apply anti-seize compound on the threads of the new sensors and install them by hand to avoid cross-threading. Tighten to manufacturer specifications (typically around 30-40 lb-ft).
6. Reconnect Connectors: Plug the electrical connectors back into the new sensors.

3. Replace Catalytic Converter (if necessary)

1. Remove Exhaust Components: If the catalytic converter is damaged, remove any exhaust components connected to it (such as bolts and brackets).
2. Disconnect 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 with bolts. Torque the bolts to the specified value.
4. Reconnect Exhaust Components: Reinstall any previously removed exhaust components, ensuring a tight fit to prevent leaks.

4. Reset OBD-II System

1. Reconnect Battery: Reconnect the negative battery terminal.
2. Clear Codes: Use an OBD-II scanner to clear any stored trouble codes from the vehicle’s memory.