LS Standalone DIY harness

[FAKKY]

Guys
who has done this themselves for their ls swap ?

[Dustytrix]

I have done several.

[FAKKY]

Awesome.
Looking for someone to either push me into it or to not do it.
Never done wiring before - but I havent rebuilt a trans before and about to do that also

From my researach ..... "seems" simple enough ...

This is a for a purchased a LQ4/4l65e out of a 2007 hummer.

Looks like all I need is


1) Follow the harness depinning pinouts here for C1/C2
http://www.lt1swap.com/2004vortec_pcm.htm


2) Buy the relayed factory harness mod kit you have for soldering/splicing power for the ECM hot/Coils/TAC/inj/AC etc - basically reroute from main original fuse block what is kept.
https://www.bp-automotive.com/produc...i-24x-engines/


Anything else to it ?

How do most people run their AC - off the PCM control ?

[binford]

That fuse block doesn't look to have weather tight connections. I'm sure you could find something more OEM. I pulled a bunch of weather tight relays at PickNpull and still have several extra in my bin.

If you go to the LT1 site, at the top in the middle is a link to videos of him reworking a harness. I found them very helpful in pushing me to get mine done.
I did a TBI harness year's ago.

If you have a truck harness you have it easy.

Found link Summit

[Wildkarde]

you dont need weather tight for the power stuff, the factory underhood fuse panel isnt weatherproof.

If you have a decent understanding of wiring, the info at lt1swap.com makes it a really simple process. Time consuming and tediuos but not really difficult.

[Dustytrix]

The harness pinout link may or maynot be what you need, 07 was a style swap for gm. I don't think it would affect harness though. But look at your ecm and harness and see if the wires match up to pinout list on lt1 swap. Also I like the Bp fuse block you linked. I have never used it but it looks like a great piece to me. I used the block listed on lt1 swap, its not nearly that nice. Yes use ecm to control ac, unless you are going vintage air. Its self controlled.

[Wildkarde]

As long as it's an old style computer with the long connectors that use a bolt in the center to lock them and not the newer style computer that pinout page is correct.

[FAKKY]

Originally Posted by binford

That fuse block doesn't look to have weather tight connections. I'm sure you could find something more OEM. I pulled a bunch of weather tight relays at PickNpull and still have several extra in my bin.

If you go to the LT1 site, at the top in the middle is a link to videos of him reworking a harness. I found them very helpful in pushing me to get mine done.
I did a TBI harness year's ago.

If you have a truck harness you have it easy.

Found link Summit

thanks for link

Originally Posted by Wildkarde

you dont need weather tight for the power stuff, the factory underhood fuse panel isnt weatherproof.

If you have a decent understanding of wiring, the info at lt1swap.com makes it a really simple process. Time consuming and tediuos but not really difficult.

Thats what it looks like - but dont know what I dont know
Mainly split and depin wires to cleanup.
Route injectors/coils/tac to new power circuit all supplied by eitehr constant or key on.

Originally Posted by Dustytrix

The harness pinout link may or maynot be what you need, 07 was a style swap for gm. I don't think it would affect harness though. But look at your ecm and harness and see if the wires match up to pinout list on lt1 swap. Also I like the Bp fuse block you linked. I have never used it but it looks like a great piece to me. I used the block listed on lt1 swap, its not nearly that nice. Yes use ecm to control ac, unless you are going vintage air. Its self controlled.

Yeah its the green/blue connector and lq4 6.0 not the 6.2. But .... not sure how to know if certain wires changed etc.

NOt sure what AC unit I am going with ...... do I need to decide now ahead of the rewiring/harness side - never done before

Originally Posted by Wildkarde

As long as it's an old style computer with the long connectors that use a bolt in the center to lock them and not the newer style computer that pinout page is correct.

Thanks - yes its the green/blue style P59 or wahtever i believe.
Heres a an actual pic.

[ls1nova71]

That's a Gen3 engine from an early '07, so just use the diagrams on Lt1swap.com for a 2003-2007, they're the same. As for the A/C, probably not going to be able to run it through the PCM since starting in '03 they went to a serial data controlled A/C request rather than the older 12v request. There are ways around it to an extent, but usually easier to just run the A/C separately.

[FAKKY]

Originally Posted by ls1nova71

That's a Gen3 engine from an early '07, so just use the diagrams on Lt1swap.com for a 2003-2007, they're the same. As for the A/C, probably not going to be able to run it through the PCM since starting in '03 they went to a serial data controlled A/C request rather than the older 12v request. There are ways around it to an extent, but usually easier to just run the A/C separately.

Not the same LS1NOVA/one guys garage over at ls1tech ?

Anyway - thanks.
here's what I dont get (mostly).

1)
How do you know that every wire in the 2003 harness is the same as a early 07. meaning for example
Maybe its says de-pin wire 96 for and O2 sensor. But in 07 its actually something else thats critical for trans - how would you know ?
All im going to end up doing is basically blindly following that link for depin


2) AC - had read that somewhere - good to know for sure.
I dont really get AC in terms of its basic functionality using the compressor/evaporator and hiugh/low pressure of gases etc.

So in terms of wiring it up as a seperate standlone system - what do I need to know/understand and think about. IS there a good build thread out there that sort of shows/explains it ?

I havent decided on a AC system yet.
Its likely to be a vintage air. But was waiting till I decided if the low mount AC will fit or not and what brackets I need to do the relocation etc.

Sorry guys - EVERYTHING on this build is new to me.
First time on everything.


Appreciated.

[kipps]

Originally Posted by FAKKY

How do you know that every wire in the 2003 harness is the same as a early 07? meaning for example, maybe its says de-pin wire 96 for and O2 sensor. But in 07 its actually something else thats critical for trans - how would you know ?
All im going to end up doing is basically blindly following that link for depin

If your harness is completely unwrapped, it should be simple enough to confirm that the wire actually goes where the de-pin list says it goes. If not unwrapping the harness, I'd use a multi-meter to check conductivity on that wire-- to make sure that pin actually connects to a rear o2 sensor, for example.

Originally Posted by FAKKY

So in terms of wiring it up as a separate standalone system - what do I need to know/understand and think about. IS there a good build thread out there that sort of shows/explains it?

I've wished for the same thing. Sure there are youtube videos, but for the moment I'm online with the speed equivalent of dial-up, so videos are out. I'd like to see a build thread with pics and recommended tools for re-pinning harnesses.

Also, I'd like to see a thread describing how to de-pin and re-pin the various stock connectors on these trucks, such as steering column connector, dash, lamp holders, etc.

[Jason Banks]

I think this guys videos are great:

https://www.youtube.com/channel/UChS...dctSg/featured

UCanDoIt2

[FAKKY]

Yes seen a few of those videos as well.

In essence though its a simple as

1) Depin According to LT1SWAP site
2) Route and lengthen according to taste
3) Join the wires that need constant/ignition +12v to a fused block control like

https://www.bp-automotive.com/produc...rness-mod-kit/


Then for AC/Fans later ....... just use a seperate harness or extend existing harness etc.

Isn't fan controlled via PCM also ?

[binford]

Yes fans can be controlled by the PCM. LT1 adds pins using wire removed from other pins.
I control my fan in another vehicle, by having a tempature switch installed in the radiator hose. Metal section that fits in the hose.


If you have the transmission, that too is controlled, needs to know when to lockup.
If you have a dbw gas pedal that is controlled too via TCM

You can feel like it's getting over your head, but read a few more pages on LT1 and it helps to understand .
Thats what I've been doing

[FAKKY]

Thanks - Ill check out LT1SWAP for some more references regarding fans etc.

I think Ill probably just jump into it ...... like the idae of being able to customize the harness length and also just another thing in the truck was done by myself ....

thanks all

[binford]

FAKKY There are guys that do a total custom wiring harness, I found one that routed all the wires to the rear of the engine. They started by pulling every wire from the harness, coiled them up and started from scratch.

My first question would be where is everyone mounting their PCM?
I need to figure that out first.

I took my harness and put it back on the motor to see where I could put the PCM. Well the harness reached to the back of the transmission so it will fit just about any where.

Trying to find info on this truck, see how they rerouted the wiring, and running stock A/C location. was posted by user Farmtrucks posted in LSX swapper pic thread

[Wildkarde]

Originally Posted by binford

FAKKY There are guys that do a total custom wiring harness, I found one that routed all the wires to the rear of the engine. They started by pulling every wire from the harness, coiled them up and started from scratch.

My first question would be where is everyone mounting their PCM?
I need to figure that out first.

I took my harness and put it back on the motor to see where I could put the PCM. Well the harness reached to the back of the transmission so it will fit just about any where.

Trying to find info on this truck, see how they rerouted the wiring, and running stock A/C location. was posted by user Farmtrucks posted in LSX swapper pic thread

Thats how I do it when I build a harness for someone. Makes for such a cleaner looking harness and once you get the hang of it doesn't take much longer unless you are going to shorten the wires instead of just folding them back on themselves.

As for length, the later harness with the blue/green connectors are quite a bit longer than the earlier blue/red ones for some reason.

[FAKKY]

This guys uses a subharness --- but if its long enough already - probably not required.

https://www.youtube.com/watch?v=YqItuKS_Cew


Im not too sure on the PCM mount as yet ......... due to not having AC in place.
It will be inside the cab somewhere or behind my seat - but I have a panel truck

[BR3W CITY]

Originally (2010ish) my PCM was mounted (along with my fuseblock) on the drivers side inner fender. Easy to get to, and no problem routing the wires at all. As the swap game evolved a bit, I moved my computer into the area above the passenger footwell, partially tucked behind the blower box.

[TCCGRIZ]

Sub'd

[Clyde65]

I saw where someone put theirs in the deluxe heater box on the FW, had to fab a little but.

I put my cruise control module in my heater box.