Where is bank 2 sensor 1 on a 4.3l 2001 Chevy silverado?

On a 2001 Chevy Silverado 4.3L, Bank 2 Sensor 1 is located on the passenger side exhaust manifold, near the engine block. It's the upstream oxygen sensor on that side. "Upstream" means it's closer to the engine than the catalytic converter.

Remember that locating the sensor can be tricky due to heat shields and other components. Using a repair manual specific to your vehicle's year and engine is highly recommended for precise placement. A visual inspection with the help of diagrams in a manual will be the most accurate way to find it.