If there is one, it will be a black plug with 2 wires in each of 2 rows for a total of 4 plugs, and {when new}, had a cap on the plug that has only 1 wire that loops back into the plug (to keep the dust cap from getting lost). I look for that 1 wire looping back into the plug, and it is usually on the harness, near where the engine/emissions harnesses connect to the truck harness, where the harnesses run over bell housing.
looking directly into the plug connector, you -may- be able to see the markings for a through d plugs to see which pin is which letter.
The IFAK cable is the "can box" cable that is also a USB connection to the computer for the Dealership's proprietary software. The dealership's software looks at everything connected to the 'can' bus [which includes the emissions controller, among others], but the diagnostic connection [that I describe above] only communicates with the Emissions controller.

If you tell us more about the problem that you are hoping to be able to fix with this information, we may be able to better assist you with getting your truck fixed, quicker.