The oil pressure sending unit on a 3.1L GM engine (like those found in various GM vehicles from the late 80s and 90s) is typically located on the
passenger side (right side) of the engine block, near the front. It's usually a small, threaded device with one or two wires connected to it. It's often near the oil filter, but not always directly on it.
You might need to consult a repair manual specific to your vehicle's year and model for the precise location. A picture or diagram would be immensely helpful for accurate identification.
