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

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

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.

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.

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.

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.

does the engine have spark and fuel while cranking

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.

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

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

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

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Originally Posted by 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

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Agreed. I pulled my hair out over that ground on the bottom of the block. Called Casey "Man why won't this thing fire? - Crawl under the truck, check this ground, call me back in 5 minutes I want to hear it running" done.

Yea I know their were two black wires on passenger side harness that didnt have any sensors to them we grounded one but not the other. Prob try and ground the other and see what happens.

Ok got my engine to start yesterday! not sure if it was the new pcm or the fact there was one ground wire that was still yet to be grounded. once we grounded that wire engine fired like a champ! Stupid grounds

Good deal! I love it when a plan comes together ;)

yes Sir! I will posting a new thread in soon, that will have all my parts i had to buy, modifications, and changes for this conversion. For people that are interested, because it was a slight pain and it just doesnt drop in and work. But worth it!

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Originally Posted by wesleyland

yes Sir! I will posting a new thread in soon, that will have all my parts i had to buy, modifications, and changes for this conversion. For people that are interested, because it was a slight pain and it just doesnt drop in and work. But worth it!

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There's already quite a few threads on the swap. You didn't break any new ground.

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Originally Posted by wesleyland

Ok got my engine to start yesterday! not sure if it was the new pcm or the fact there was one ground wire that was still yet to be grounded. once we grounded that wire engine fired like a champ! Stupid grounds

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^ AWESOME!!! Glad you got her running, now post up a video of that motor purrrrrrrrrrr'n away in there :)

Glad to hear it.!!!

Yea I can put one up. Right now we are swapping intake manifolds on it. I have a video but it shows us starting the engine and it catching fire haha! there was a small leak in the fitting on fuel rail line. No damage luckily.