Custom LSX Wiring Harness Build

Trucking Into The 21st Century!

Eric McClellan Jan 16, 2014 0 Comment(s)
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For a lot of you guys out there, like us, you're probably cash strapped and budget conscious. You may think that wiring is too challenging and difficult to tackle yourself, but if you follow along with us, you'll see that if you go slowly, and break each sensor down to its each individual components and wires, it's not as bad as it may seem.

Admittedly, wiring is not our favorite thing in the world to do. So, we went to our local LS guru and custom fabricator of all things GM LS, Nate Shaw of One Guys Garage, in Lakeville, MN. Nate has seemingly made a ton of these wiring harnesses to custom lengths, so it's something that almost comes natural to him at this point. His ultimate goal is to strive for an “invisible” wiring harness that is completely functional, but leaves car show visitors scratching their heads. So for that, we knew we had the right guy for the job.

We were able to snap a cheap wiring harness, from a LS truck engine and combine it with a few off the shelf parts. You'll be able to build yourself a custom sized wiring harness for under a $100. To be fair, this project will require a decent amount of free time. However, it's a great way to get into the LS engine family for the guy who has a lot of time on his hands, but not a lot of cash in his wallet. Be prepared to spend anywhere from 8-12 hours on the build.

Wiring Harness 2/28

The best advice we can give to anyone right of the bat is to go slowly. The first time you do this job you may become lost. That's normal, so give yourself plenty of time, and have an entire crash carts worth of patience. We have included a spreadsheet with all the pin outs for the typical 1998-2002 Corvette wiring harness. Don't worry; the pin-outs haven't changed much over the years, which we really have to give GM credit for. If you completely strip the PCM connectors, like we have, and only plug in the parts you need, you'll be ready to rock in no time.

Parts List: Source:
LS Truck Wiring Harness - Junkyard
(1) OBD2 connector/port 829-12110250, GM #12129373 Mouser Electronics
(4) OBD2 terminal 829-12129373, GM #12110250 Mouser Electronics
(2) Terminal lock 829-12160437, GM #12160437 Mouser Electronics
(8) Relay terminals 571-42238-2 (These are replacement Mouser Electronics
terminals for the relay sockets (so you can use your own wires if desired)
PCM Terminals (pack of 100 for extras)
18ga wires, GM# 12084912 Mouser Electronics
20-22ga wires, GM# 12084913 Mouser Electronics
(1) Universal 30amp relay and socket from Dakota Digital. Summit part number DAK-RLY-1. One will power the whole engine harness. Additional relays required for fuel pumps, fans, etc. 
(1) Fuse block, Dorman 85668, Summit part #RNB85668

2000 Chevrolet Suburban Suv Wiring 3/28

1. Here’s what we are starting with: a wiring harness out of a 2000 Chevrolet Suburban SUV. We were able to score this bad boy for $25 from a local junkyard. It was such a bargain that we bought two! It originally came wired for an automatic. More specifically, this was designed to fit with a 4L60E transmission, but we are going to upgrade it to use it with the 4L80E for its robust strength, as we are looking for something that will handle over 600 horsepower. For the purposes of this build, you may use whatever port you wish, to match the transmission you’re going to use.

Wiring Harness Clear Coverings And Plastic 4/28

2. We start out by clearing all the wiring coverings and plastic retainers. This will help us get a visual of the harness, and get it down to the basics, so we can route every wire exactly where we want it to go.

Wiring Harness Take Pcm Connectors 5/28

3. You’ll now need to take the PCM connectors apart to get to the wires. The back cover just clips into the metal holder. Make sure to take care and not snap off the clips, so it can go back together smoothly. The front cover (blue or red) slides off easily with a small pick.

Wiring Harness Remove 6/28

4. An easy trick to removing the wires is to use your fingernail and pry up slightly to get the wire to come out. That’s one good reason to not chew your nails too closely. Now is a good time to label your PCM connectors so you don’t get lost.

Wiring Harness 7/28

5. Here’s a perfect opportunity to pull out your wiring diagram. We’ve supplied one in this article so you can follow along. This has been your fair warning; going on from this point takes a fair amount of concentration and attention to detail. In the end, it might just be worth it.

Wiring Harness Old 8/28

6. A harness has a lot of tape and sheathing. We plan on using a more aesthet- ically pleasing covering, so we can pitch this old dusty junk. You can reuse this if you want; it’s your choice.

Wiring Harness Laying Out 9/28

7. Laying the harness out helps you get a visual of where things need to go. It also keeps things in order and organized. Before we get any fan mail; no, this is not our kitchen.

Wiring Harness Pcm Connector 10/28

8. Notice how each of the PCM connectors are numbered accordingly? Each side, red and blue, look very similar and are numbered with each pin doing a very specific job. Follow the spreadsheet we’ve provided, to find the correct pins for each of your sensors. Again, go slowly and be deliberate.

Wiring Harness Remove Wire 11/28

9. Now, we have to cut or remove all of the wire terminals so we can only make the correct connections when we go back to rewire the system. Notice; we labeled the PCM connectors to help us later down on the road. A good rule of thumb, when it comes to GM wiring harnesses is this: Typically, when you find a pink wire in the harness, it’s used when the key is on (“key-on” type wiring) and when you see an orange wire that is usually a 12-volt, full time power situation.

Wiring Harness Two 12/28

10. We’ll now make two separate piles, one is a wire bundle of things we’ll need later on, the other is the throw away pile. Some examples of things you might not need are the post converter O2 sensors, EGR connectors, mass airflow sensor (if you are converting to a speed density setup), AC compressor clutch wire, and transmission wires (if you are going to convert to a manual transmission).

Wiring Harness Fuel Injector 13/28

11. One of the connectors that needed to be replaced is our fuel injector connector. We plan on using the standard LS1 injectors (connector on right). If you are using the truck injectors (connector on left), you can skip this step.

Connector Parts 14/28

12. Here’s what you’ll need to complete this job: (A) These are the correct connectors for the EV1 fuel injector. (B) This is a relay you’ll need to power the harness, sensors, and injectors. (C) In descending order, the hoop connectors are used for the ground wires in the system; the final two bags of terminals will be used to rewire the PCM connectors. There is an 18-gauge wire and a 20-22 gauge wire terminal. (D) The OBDII connector is usually cut off from the junkyard, replacing it is necessary and straightforward. (E) The fuse block will be used to protect the circuits in the wiring harness. The factory harness will typically incorporate this in the main fuse block, since we can’t take the entire fuse block out of the truck we have to bypass it; this is a crucial component to the life of your wiring. (F) Extra wire you’ll need to extend a couple pieces, and to the right of that, is the female blade style connectors you’ll need for other connections.

Wiring Harness Final Piles Of 15/28

13. Here are our final piles of wires. The closest wires are the ones we plan on throwing away and the tightly bundled wires in the back are the wires and pigtails we are going to reuse.

Wiring Harness Injector Driver 16/28

14. We had to purchase an injector driver box to help us run our low impedance injectors. Because the motor we are putting this on will require some massive injectors, it was cheaper in the long run, even with purchasing the injector box. This step isn’t necessary if you are going to run high impedance injectors. Just note that we wanted to include it as a less expensive alternative to fancy injectors.

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