First swap

[Jarrett Dixon]

I have a 98 GMC sierra OBS with a 4.3. Just purchased a 2004 5.3 DBW with complete harness and acc. I sent the harness to a buddy of mines to make it standalone. My question is what wires do I need to save from my factory harness. I see some people run both computers for abs. Is there any other way of doing this? How does the ac system work without the old computer? How do I send signal from the ignition key to the new computer? Bare with me its my first swap!!😕😕

[super10brss]

I've never done a swap... but have done LOTS of research and "think" I have a few ideas.... so take this advice with a grain of salt.

My question is what wires do I need to save from my factory harness. I see some people run both computers for abs. Is there any other way of doing this? ����

When you take everything apart make extra sure you label EVERYTHING that comes off the truck. For example there should be two wires going to the starter. One big wire that comes from the battery (that one will go back to the new LS starter) the small wire is your trigger wire for the starter to engage. When the harness guy sends back your harness there "should" be a starter wire I believe. So from old 4.3 small gauge starter wire to harness wire that says starter.

No clue on ABS... jerked mine out years ago when I did 4 wheel disc...

Other labeled wires... wiring that goes to your alternator (not sure how that taps into LS harness) the oil pressure sending unit side of block can either be put back into LS motor or you can get a signal out of the LS computer. I guess it's kind of up to the harness guy what previsions he leaves coming out of the LS computer or if he does the what 3 or 4 only wires you need to make it "run"

How does the ac system work without the old computer? How do I send signal from the ignition key to the new computer? ����

If I am not mistaken the AC system (at least on my 89.. things changed for the "vortec" trucks in 97? or 98?). I plan to use my R4 factory AC compressor with a Holley LS swap bracket and let the trucks factory bcm (body control module) do its thing. Shouldn't be too hard to find a 12 volt on under the hood when the key is on... fuel gauge "should" work as normal with the BCM... seems I read some place the vortec in tank pump will provide enough fuel pressure for a LS swap (you may want to look into that. If so that factory wiring fuel pump in your tank you have will be a non issue in the swap)

Good read: http://www.lssimple.net/abcs-of-ls-swaps/

CRAP!!! guess I have a bunch more questions too!