johnsons_hotrods Posted March 25, 2011 Report Share Posted March 25, 2011 I have a 05 chevy 4.3 truck with no motor or trans and im going to put a 5.3 in its place. i have a engine and engine wiring harness will the 5.3 engine harness work with the trucks original body harness and is 2000 to 2005 engine harness the same. The 5.3 and 4l60 is out of a 2002 Avalanche. Quote Link to comment Share on other sites More sharing options...
misterp Posted March 25, 2011 Report Share Posted March 25, 2011 (edited) 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 March 25, 2011 by Mr. P. (see edit history) Quote Link to comment Share on other sites More sharing options...
mccormick steve Posted October 22, 2021 Report Share Posted October 22, 2021 n someone explain to me how i adapt this 2003 ecm to my 96 vortec wire harness ive already removed the electric throttlebody and gas pedal ...im drowning here somebody help please [email protected] Quote Link to comment Share on other sites More sharing options...
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