The Bank 1 oxygen sensor on a 1996 Pontiac Grand Prix GTP 3.4L V6 is located on the
exhaust manifold of the engine's
left side (as you sit in the driver's seat). It's the sensor closer to the engine. Bank 1 refers to the side of the engine containing cylinder #1.
Keep in mind that visual access may be limited and you might need to use a mirror or a mechanic's creeper to get a good look. A repair manual specific to your vehicle's year and model would give the most precise location with diagrams.
