The oil pressure switch on a 2001 Ford Ranger 4.0L engine is located on the driver's side of the engine block, near the oil filter. It's often a small, single-wire switch and may be a bit difficult to see without removing some components. You'll likely need a wrench (likely 7/16" or 1/2", but double check) to access it. A flashlight and a mirror might also be helpful.
Important Note: There are several components in that area. To be absolutely certain, consult a repair manual specific to your year and engine for a diagram and precise location. A picture in a repair manual will greatly increase the likelihood of finding the correct sensor.
