Where is bank one sensor one located on a 2002 Toyota MR2?

On a 2002 Toyota MR2, bank one sensor one refers to the upstream oxygen sensor located before the catalytic converter on the engine's exhaust manifold. Since the MR2 typically has a mid-engine layout, this sensor is situated on the exhaust system near the engine, specifically on the side of the engine that corresponds to cylinder bank one. You may need to access it from underneath the vehicle or from the rear, depending on your approach.