Quote:
Originally Posted by Tim john---
I also need to have a factory stock LS1 engine (2004 GTO) harness altered for a stand alone engine transplant. Would I be better off just buying one custom made or have the original altered ? I have looked at Speartech but they no longer alter originals because of current workload. Please advise. Thank You.
Tim john---
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I modified my '04 GTO harness myself. It's not as difficult as it looks but it's a little time consuming and you need the diagrams and pin-outs. Check out lt1swap.com. They have the info on the 04 GTO harness. You'll also either need to make a fuse/relay center or buy one. I'd recommend buying one from Current Performance or someone. This is the piece that turns it into a stand alone harness.
The First thing to do though, before modifying anything, is getting in contact with someone to tune your PCM. You'll need to discuss what you're keeping and what you want omitted with them, as that will change what you do with your wiring.
The '04 GTO PCM did not control the radiator fans or the A/C from the factory. Those were controlled by the BCM. So, if you want to change that you'll need someone who knows how to fix that part of the code.
I have the same PCM as you and had it reprogrammed to control the fans and AC. IIRC, my tuner started with the calibration from a 2005 safari van (same PCM as GTO) because it controlled the fans. I think there are also snips of code I there from a vette, ctsv and some GM prototype vehicle (for the A/C).
Anyway, the tuner and harness kind of go together at least in the case of this particular harness. Of course, if you will control the AC and fans via some other means it's not such a big deal. I just wanted mine fully integrated.
Another option is to buy a complete harness and PCM that's already stand alone and just sell what you've got. If you don't want to deal with any of the above, that's probably the easiest option.