1936 LS1

iTrader: (10)

I'm sure theres a good reason (or 12) but I'm curious as to why a stock harness must be modified for a hybrid. If it physically fits your application where do the problems arise?

BTW, I have an '05 Silverado harness (DBW throttle body) and PCM for my street rod and I'm trying to decide if I want to just sell it and buy an stand alone harness or pay to have this one modified.

bczee

iTrader: (12)

The OEM harness is designed to be connected and intergrated with other harnes (Body, Brakes, Cruise Control, other emssions and function.

Without those other harness connected and giving inputs, then Engine and PCM will not function. By modifying the harness. You can do away with the other harness (BCM and others).

You really only need a few mods to the harness to turn it into a Standalone harness, +12v battery, +12v Ign. and Grounds.

The other you can get around, but you may as well use then; Fuel pump, Serial (ODBII connector), Fan Relays, Tach, VSS output and a few others that are handy to be using, but you can get around them by using standalone system, the Fuel system is one, and a Standalone Fan/relay is another.

Intergrading a fuse box is also a good idea.

but as you stated, there are about a dozen other reason and work arounds. But unless your removing many other wiring system and harness the un-modified engine wiring and PCM will not fire up..

VATS is another item you need to work around with, it requires the BCM system along with the Steering Column and Key.

1936 LS1

iTrader: (10)

Thanks for the quick and thorough reply. Guess I better start saving up for a harness.

Think I should have this one modded or buy a pre-fabbed harness?

bczee

iTrader: (12)

If you have the time and a bit of skills.. (soldering, splicing, etc). and reading the FAQ for wring and pin assignements.. you can do it yourself. But look around, you can sometime fine pre-modified harness or someone that will help out and do it for a good price.

If you can afford it, Speartech (John), Current performance, Wait4meperformance (Jesse) and other vendors do a great job of mod'in them and working to intergrade them with your cars systems or selling you a new one.

Either way.. they usually work ok.

Shon Herron

iTrader: (25)

huh?
we take the stock harness and either leave everything in there or take out some of the things we are not going to use, ie A/C, EGR/AIR, etc and then hook up <10 wires and run them all day long after PCM programming.

1936 LS1

iTrader: (10)

Shon,

Are you saying that PCM programming (to delete stuff you're not using) is all you do to make 'em work?

Richard

Shon Herron

iTrader: (25)

That's what we do. Turn off VATS, make what ever other changes we want in the tune, hook up the few wires for ground, ignition, 12V, FP relay and turn the key, fires up.

VATS removal is one of the biggest keys here....

bczee

iTrader: (12)

That is what I stated in my 1st reply post to him..

Shon Herron ... are you a vendor or a shop that provides these services ?.. if so.. what are your cost for modifying a harness to standalone and for a basic Mail order tune/flash ?

LS1MCSS

iTrader: (18)

If you can do a conversion swap, you can mod your own harness. I used to think it would be complicated, until I did the first one. Just sign up at Alldata DIY. It will cost about $25 for one vehicle per year. You can print all of the schematics you will ever need to mod your own harness. Every seperate section of the powertrain wiring will have its own schematic, like power connections for the engine, ignition, smog, injector, and so on. After you study the schematics for a bit you'll realize how easy it is to go through each one and remove the wires you don't need.

Shon Herron

iTrader: (25)

I am not a vendor for this site.

Most of what one needs is on this website or a few others,

johnLs1camaro

iTrader: (28)

honestly the harness is not that hard to do, also if you dont want to theres a guy on ebay that does then for a cheap price, and also tunes your pcm while hes at it. its like $200 bucks and he does a great job.

rotor vs. piston

iTrader: (3)

Here's what I did, got everything running w/ the harness the way it came out of the car, '04 GTO, had the PCM programmed to remove the emissions stuff other than the first set of O2 sensors. Pretty easy, few power wires, ground, and fuel pump relay... = VROOM.

From there I removed the connectors I didn't need anymore, along w/ most of the wires. I left around 6" of each wire as a "just in case". Then rewrapped the harness and re-added the corrugated tubing.

johnLs1camaro

iTrader: (28)

dont forget about the vats either

LS1GMCTruck

iTrader: (2)

The best reason to modify an existing harness is to simply clean it up, reduce its size, & shorten or lengthen wire/plugs.

rotor vs. piston

iTrader: (3)

This, my gf said "it looks a whole lot better". It's just more aesthetically pleasing when you get all of the vestigial stuff out of the harness and maybe run things in a different way from factory to make it neater.

Steve VanS

iTrader: (1)

We used our '99 FBody harness as is. You can un-wrap the harness and remove wires if you want to, but you risk removing the wrong wire(s) and / or damage to needed wires from flexing the harness, etc. If you use dual fans, A/C, EVAP system, most of the wires are used anyway. Our installation deleted the EGR and AIR systems.

rockytopper

I agree I did the same. The uglest thing about the ls engine is the coil packs on top of the valve covers. If you ain't going to do something about that the difference in a 1 inch trunk harness and a half inch want make much difference in appearance. If you need to lengthen the harness to relocate the pcm or just want to hide every thing as much as possible then I see a need other wise leave well enough alone. If it ain't broke don't fix it.

Rodder

iTrader: (2)

I didn't mod my harness at all--I bought connectors to plug in to the stock harness. Someday I need to rework it to remove unused wires and relocate the PCM.

BulletBird

The 36' chevy looks fantastic, I'd like to be able to check it out someday. Thanks for all of the good info on the harness, this is something I have to figure out myself.

Rodger

Chevy-art

iTrader: (4)

I also read this before, no need to modify it just get power and grounds. And hook up to gauges.