To be absolutely certain, you should:
* Consult your owner's manual: This is the best source for the exact location in your specific vehicle.
* Look for a label: The PCM itself might have a label indicating what it is.
* Use a repair manual: A Chilton's or Haynes manual for your vehicle year and model will have diagrams showing the location of all major components, including the PCM.
Searching online for "2003 Ford Explorer Sport PCM location" with images might also help you visually identify it. Remember to be careful when working near any vehicle electrical components.