well that sounds like the cable diagnozer uses.

a square rectangle'ish plug with 2 rows of pins, the connector has some special ridges that allow only it to fit in the female connector on the truck harness. The end that connects to the pc side is a db9 serial and with today's computers you will need a usb to serial adapter. The newer cables they have may have a usb connector on the pc end now but the older cables had db9 serial.
You can only obtain these cables from caterpillar officially. An aftermarket solution MAY be available but i wouldn't hold my breath on that, they are not in the practice in letting their proprietary software or hardware out, it is dealership specific and only given to trained technicians and the software is tagged to the computer service tag it is installed on.