The oil pressure sending unit on a 2000 Ford Ranger is located on the
engine block, near the oil filter. It's a small, usually one-wire, sensor. However, the exact position can vary slightly depending on the engine (2.3L, 2.5L, 3.0L, 4.0L). You'll likely find it on the driver's side of the engine.
To be certain, you should consult a repair manual specific to your Ranger's engine. A Chilton's or Haynes manual will show you a diagram with the location clearly marked. You can also usually find diagrams online by searching "[Your Ranger's engine size] oil pressure sending unit location."
