1999 silverado stalls immediately

[Jvan83]

I know these trucks have a passlock3 system,however this truck has something unique I think. When you first turn the key a clicking can be heard from behind the dimmer switch/4x4 selection (a module does sit back in there) sounds like a relay however it is not its the module. When you turn the key to start the truck it starts and the clicking can be heard(again) and truck stalls all within 2 seconds. My other truck same year does not do this (the clicking noise). I am curious as too if this module may be the cause of the stalling issue and if so what module is it. At this point I am 90% certain of this however I inherrited this problem after my friend spent alot of money rulling out mechanical issues (brand new fuel pump,brand new fuel regulator,new body control module) and still same results.