To be certain, you should:
1. Consult a repair manual: A Haynes or Chilton manual specific to your 1993 Ford Ranger 4.0L V6 will have a diagram showing the precise location of the sensor. This is the most reliable method.
2. Look near the oil filter: This is the most common location. Carefully inspect the engine block in this area. The sensor is usually a small, cylindrical device with a single wire connector.
3. Use a visual inspection: If you're comfortable looking under the hood, carefully examine the engine block, focusing on areas where oil lines and the filter are located.
Remember to be cautious when working under the hood of a vehicle. Ensure the engine is cool and off, and disconnect the negative battery terminal before starting any work.