Yup, sounds like standard PMD / FSD failure. It's a little black box that was mounted on the side of the injection pump from the factory. If it's still in that location, you need to purchase a PMD, PMD extension harness, and a PMD remote mount to locate it in a cooler location.
On my 1995 model, I have a D-tech FSD mounted on an FSD cooler right in front of the driver's side battery where it receives air flow from a hole in the radiator support.
Search for PMD failure, and you'll find tons of info.
Casey
1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter