You can pull out the relay and check the outside of it for a diagram for which pins are the control side and which is the load side. Most relays have a pictures on the side or an indicator showing the way the pins are. If you know which pin is which you can check for voltage/ground coming in to the relay from the ECU. You need to know if it's a ground side switching circuit or a positive side switching circuit. If you're having problems finding which pin is which inspect the wired coming in and out of the back of the fuse cavity. Bigger wires are the load side and smaller wires are the control side. This is a "general" type description since I'm not a jeep tech but i see you know your way around a meter so I posted.
If this helps please accept my answer, thanks
The cooling fan relay in this vehicle doesn't even have any pins. It uses a "solid state" relay with transisters and they do have a lot of problems with them.
You need to check a few things first.
Make sure the fan motor itself is good by jumping power to the Dk Grn wire and jump ground to the Bk/pk wire. The relay is responsible for applying both.
Next check the #10 fuse which is 40 A
If all this checks out, your only leaving the wiring, the relay or the PCM.
The relay is the most likely cause of that problem if the motor is good.
The next problem is finding the relay. they hide it well. here's the location. It's hidden behind the right headlamp.
The Pulse Width Modulated (PWM) cooling fan relay is located below the right headlamp behind the bumper fascia.REMOVAL
I figured it would be something like this, that's why i stated my answer was general in nature. Sorry if I confused you.