To be absolutely certain, you should:
* Consult a repair manual: A Haynes or Chilton manual specific to your 1993 Chevy Lumina will have diagrams showing the exact location.
* Use a parts diagram: Many online auto parts stores (like AutoZone, Advance Auto Parts, etc.) allow you to enter your vehicle's information and view diagrams showing the sensor's location.
Looking at diagrams and pictures online will be significantly easier than trying to find it blindly. Remember to be careful when working around the engine, and disconnect the negative battery terminal before starting any work.