Can anyone tell me how to do this? Ive got a 4.3 that I've did an engine swap on and can NOT for the life of me get it to run. Starts up about for about a sec. then dies. Ive replaced everything in the fuel system, replaced all fuses that pertain to ECM/Fueling, checked everything that i know to check. Ive also tried the Passkey III relearn 5 times with no help, it says that you will have a security light on, and i dont. The truck will start and run fine if manually fed gas. I dont know what else to do.

 

turn off the vats in the tune and i bet itll start right up.