2000 silverado 4.3l to 6.0l swap...wont start

[wesleyland]

hey all, I have recently undertook a swap on my 2000 silverado. I am swapping in a 2003 LQ9 from a cadillac ext. I have the engine sitting in my truck. Made a conversion from its drive by wire to drive by cable to simplify things. The harness that came with engine was spliced, so i had to get one from junkyard from a 2001 5.3l tahoe. Well harness wont work with the 6.0l computer because harness has red and blue connectors and engine computer had green and blue. So I aquired a new computer to fit harness and had it reprogrammed to everything. Engine will crank but wont start. Any thoughts on this issue? I feel like I am very close but just missing something.

Thanks

[Frenchy]

You've made a royal mess of it. Your truck isn't gonna function with that PCM or harness. You need a 99-02 truck PCM and Harness.

[wesleyland]

I now do have a 99-02 pcm and harness, all of the connectors match up. I have a sensor here or there that arent the same but nothing that shouldnt hold the truck back from starting. I spoke with the guy reprogramming my ecm and he thinks its a security issue where thins cant communicate correctly.

[Frenchy]

VATS needs tuned out. There's also a ground, drivers side, bottom of the engine block. If that's connected, the truck will crank but not fire.

[wesleyland]

yea he is suppose to take VATS out and tune it. Im sure if i got a 2000 - 2002 engine it would have made simpler since pins changed in 2003. But since i have 2003 engine, the harness and pcm of a pre 2003 v8 so it will pin correctly to my truck. It should work unless I am forgetting something.

[farmtruc]

does the engine have spark and fuel while cranking

[wesleyland]

yea it is dumping fuel to the fuel rail. Spark I am not so sure of. But I do think the previous pcm was a bust and halfway worked. I should be getting a new one in end of this week.

[farmtruc]

if the injectors are squirting fuel, it's not vats.

[wesleyland]

hmm ok, I know the security light inside the pickup keeps blinking security when the key is forward or i try to start it.

[Kritical Flaco]

Double check and check again all your grounds....most times its the smallest things,that cause biggest headaches...hope u get it resolved soon