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4.3 To 5.3 Wiring Question

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MODERATORS - Please move this to the correct section.


SITE OWNERS - Please rename the How-To section to something else to avoid confusion.


ORIGINAL POSTER - the How-To section is where you contribute knowledge, not ask how to do something; read the sub-forum descriptions first.


Answering your question -


I have wired a 5.3L in a 2000 S-10 that originally had a 4.3L, including climate control; this is very similar to what you are proposing.


The engine harnesses are identical, EXCEPT the climate control - GM changed the way the A/C high-side pressure switch/sensor works in the 2003 model year - because of that, 2002 and older harnesses AND their PCMs are different than 2003+ equipment; in 2002 and older trucks GM used a switch, in 2003+ they use a pressure sensor.


You need an engine harness from a 2003+ V8 truck to make your swap work; the existing PCM *should* work with just a complete operating system reflash, but I could be wrong there. If you need a '05 PCM contact gasemall, he's got 3 PCMs from late-model trucks that had 6.0Ls in them, I am sure he'll sell you one for a good price.


I have seen another person (not on this forum) do a 4.3L -> 6.0L transplant and that truck had several electrical demons, the source of which we never arrived at an answer to but IMO because he reused the existing 4.3L PCM and reflashed it with a 6.0L operating system, and eventually he got frustrated and sold that truck. Problems encountered were related to 4L60 shifting behavior, and it very well could be that in his effort he crossed a wire in his donor harness because he got a butchered on. I don't know if he ever got it all sorted out but I would spend the extra $$$ and source a matching '05 V8 PCM & engine harness, since you have an '05 truck with '05 BCM, dash, and climate control. My 2-cents.


Hint - invest $25 in a bootleg copy of the GM ESi service manual.


Mr. P.

Edited by Mr. P. (see edit history)
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