i have a 2000 silverado, came stock with the 4.3L v6 engine which I have removed completely with transmission and pcm & harness...I installed a fully built ls1 engine and it’s origi 4l60e trans I used a harness out of a 2001 silverado 5.3l which plugged in straight into my pcm... I’m having trouble getting it started I have plugged everything in and the key doesn’t seem to make the truck run...I tried starting it from the solenoid and started by touching the two leads and it seems to crank and it turns on for a quick second and than it shuts off...I have spark and fuel pressure....a friend of mine said maybe because the pcm belonged to a camaro and the truck wiring is diff might be the issue ...another said to make sure all the grounds in the harness are connected...any suggestions or past experiences anyone had related to this issue?