Many of them (Sports) did not have fobs, though I don't know if it was impossible to order one with it or just not how they typically came equipped from the factory. It's the same receiver "RAP" module that does the keyless entry keypad on the door.
If you do have a keypad on the door, you have this module. You might be able to DIY add the module but you may also not have the wiring harness to its location, which is in the cargo area left side rear behind the trim panel.
There are various topics with pictures of the module and part #, including the following. The wiring harness, you might have to pull off a donor at a junkyard, might be a bit of work to get it all and I'm not sure how it (mechanically) connects at the other end, but it'd be obvious on the donor vehicle.
My remote entry system has been acting up and finally stopped working. Not a great calamity but a royal pain in the arse when one is accustomed to using the remote. The culprit in this situation was the RAP module ( Remote Anti-theft Personality module ). The little “black box” ( which is...
www.explorerforum.com
If you try to add one, there may (or may not
) be wiring diagrams in my sig that show the circuit diagram, but you may not need them if you get enough of the wiring /connectors from the donor vehicle, though it might be a bit of work to do all this.