The oil pressure sending unit on a 2001 Chevy Silverado 1500 is located on the
driver's side of the engine block, near the oil filter. It's a relatively small unit with a single wire connected to it. However, the exact position might vary slightly depending on the specific engine (4.3L, 4.8L, 5.3L, or 6.0L).
To be certain, you'll need to consult a repair manual specific to your truck's engine. A visual inspection with the engine bay somewhat clear (not overly cluttered) will help locate it. Look closely around the oil filter; it's usually in that vicinity.
