Where is bank 1 sensor 1 on 2008 Toyota Highlander?

On a 2008 Toyota Highlander, Bank 1 Sensor 1 refers to the upstream oxygen sensor located in the exhaust system. Specifically, it is positioned before the catalytic converter on the driver's side of the engine. To access it, you may need to lift the vehicle and remove any necessary components for better visibility. Always ensure the engine is cool and take safety precautions when working on the exhaust system.