The oil pressure sending unit on a 1999 Chevy Suburban 5.7L (likely a Vortec 5700) is located on the
passenger side of the engine block, near the
front of the engine. It's typically near the oil filter, but not directly on it. It's a small sensor with one or two wires connected to it.
You'll need to look closely at the engine block in that area to locate it. A repair manual specific to your year and model Suburban will provide a detailed diagram and will help you identify it definitively.
