i'm trying to use a wiring harness from a 2003 5.3L vortec for my 98 LS1. i have no experience with wiring and i'm completely broke so i can't really pay anyone else to do it for me. right now i'm just trying to figure out what all my connectors are so i can strip the ones i won't need for my swap as per pocket's many wiring tutorials.

 

pocket has a very good write up. what computer are you going to use? 98 ls1? or one of the later years?

 

i'll be using the stock 98 PCM

 

https://www.thirdgen.org/forums/ltx-...erchanges.html

 

isnt a 03 5.3l DBW?

 

DBW wasnt implemented evenly across the board. Trucks, vans, hi/lo perf vehicles all changed in different years

Ive had 3 03 engines and all were DBC

 

ah ok. guess he can be sure by the ECM connectors?

 

Look for the DBW stuff in the harness. If its there, it can removed during the rebuild with stuff from a JY FWD/S10. If he;'s really in a pinch, 91-92 V6/TBI cars had the correct TB connectors too, so he can reuse his old stuff

If its the pair of 80 pin PCM connectors any color combo, it will work fine. Any covers other than red/blue will need to have the tab shaved down with a razor

 

the 98 PCM is kind of the red-headed stepchild when it comes to tuning. if you're making your own harness, I'd really recommend going with the 99+ setups.

also take a look around here for more wiring info

 

i actually ended up getting a 2002 pcm. the guy who sold me the engine never sent me the pcm so i had to get a new one.

 

not to hijack this conversation but im also running a 5.3 out of a 99 truck i swap over to ls6 intake and bosch injectors ect. blah blah... can i use the computer that come with the truck harness or no. ?

 

Yes

Just about any GEN III PCM you get with a harness will work with any GEN III LSx engine. The determining factor is TB type, DBC or DBW as some newer PCMs did not come with IAC drivers. LT1swap.com has a good write up how to ID the newer ones. Your 99 will not have an 0411 PCM, but instead the older variant of it. Function and pinout is identical

 

pulling an all-nighter for some wiring fun. coffee is your friend!

bundles of wires+connectors from the 5.3 harness


3rd gen C207 and injector connectors bundled


3rd gen C100 and stuff connected to it


relays and fuses? guessing at this point.


absolute randomness left after tearing the 91 harness apart. these should be good for adding length to any other wires that need it.

 

also pocket i did exactly what you said not to and cut the IGN commons before i read where you said DON'T DO THAT. so now i have to figure out where to put those back. i've begun attaching connectors to every corresponding part under the hood to make figuring out where everything needs to go a little bit easier. unfortunately my car has been sitting in the same place since november last year, and as a result it has become the home for hundreds of huge brown widow spiders and i have pretty bad arachnophobia so after one of them ran up next to my hand i am going to be staying away from the engine compartment until i get some raid or tactical nukes or something because they freak me out. for now i'll just keep reading through the ls1 harness threads.

 

so if anyone can give me any help or advice that would be awesome. every wiring guide thread i read looks to me like: "this is a picture of the harness before you start. now this is a picture of all the connectors separated. ok now this is what the harness looks like when you're done. congratulations you're finished!" i have absolutely no knowledge of wiring and i depinned my ls harness before labeling a single wire so i'm just sitting here staring at a mess of bundled wires wishing i could afford to just buy a brand new custom made harness so i could just douse this box full of spaghetti in gas and set it ablaze. this wiring garbage is such a headache it makes me want to part out my car and buy a used kia and never drive over the speed limit again rather than take another peek at this mess.

 

you depinned before you labeled? did i read that right?

 

Well, I went carved LS for a reason. But the current project I am trying to finish for a friend is efi. Went well so far, have another good friend helping with wires, but it is still a nightmare making sure everything works. Still not sure how to make the speedometer work, oil pressure connector was cut some how and I cannot find that, so it is steady fun. Runs, engages foreward and reverse, but I will be glad when this thing is done. I may try a efi setup eventually on my 91 RS 4.8 swap, but it will be with the Vic jr and some TB I make work, I will probably trade for a setup that is drilled for the injectors, ect. All that to save from spending 1600-2000 on a efi system from professional products or msd.

 

First step is to clam down and relax

Next, open the connector ID thread and locate every connector listed. If its not listed, you dont need it. After those are tagged, use the PCM pinout list to tag each individual wire since you just ID'd the connectors

That should cover just about all the wires except for some pinks and blacks which are powers and grounds respectively. Id suggest identifying those based on what connector they're attached to, EX Bank 1 coil 12v, MAF 12v, AC grd, etc

After that, begin to bind the loose bundles into individual circuits, then drape over your engine for the mockup. Bind the bundles for a general shape

Once all the connectors are bound into one harness, you should have a huge mess where the PCM should go. This is where the individual wire tags come into play. Grab random wires and place them into the PCM connectors extending/shortening as needed

After that go over the PCM pinouts again checking for missed wires, those will be for non-sensors like powers, grounds, gauges, relays etc. Add as needed

Now you have a basic stand-alone harness fitted to your engine in your car. Take the C100 connector jumble and bind it like you did before into a neat organized bundle. Measure and attach to the stand alone harness, connect the powers, grounds, gauges and relays

Use a multimeter to test each circuit from PCM to sensor. This double checks you 1) put the pin in the right place 2) the connection is good

Loom and you're done

Im not trying to downplay the amount of involvement in this job, it is incredibly tedious and time consuming. They take me about 20 hours to build properly. So relax and start anew

 

It is very hard to sit back and look at, I hate it not matter what, rather wire everything from scratch dang near.

 

i just want to make sure i'm understanding this right: the clear c207 connector is the only under dash 3rd gen connector i'll be using? besides the c100 bulkhead connector

 

C100, C207, HVAC connectors are the only pieces of the 3rd gen harness to be retained