why does my truck fire off and immediately stop running?

Must get the diagnostic link connector (DLC) working first .. Copy & paste this video link: https://youtu.be/Bjzq8GXi3_U Cigarette lighter fuse may be blown, *which also powers the DLC* !! .. Test *ALL* fuses, inside cab & under hood!

Hi. It sounds like a fault in the ecm, bcm, computer, brain box. They are all the same part just people call them different things. Try a reset by pulling the ecm fuses(more than one most likely) and wait about a minute and put back. Your owners manual will tell you location. Your OBD2 scanner should be communicating that's why I suspect a fault or computer glitch. My OBD2 reads my Tahoe so yours should read your Silverado unless its an older tool not programmed for newer years.

does the 'check engine' light come on with the key turned on? then you turn the key and it will start , but then stall , as if fuel is shut off?