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.
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.
|LS Truck Wiring Harness -
|(1) OBD2 connector/port 829-12110250, GM #12129373
|(4) OBD2 terminal 829-12129373, GM #12110250
|(2) Terminal lock 829-12160437, GM #12160437
|(8) Relay terminals 571-42238-2 (These are replacement
|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
|20-22ga wires, GM# 12084913
|(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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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.
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.
15. From here, we need to run our wires to each of the respective items. We then run each wire back to the simulated PCM position. You can really be judicious with your placement because you are in total control of the length of the wire.
16 We placed the PCM connectors behind the motor, to simulate where the actual PCM would sit. We measured the placement in the car and came up with this location. This step is fairly critical in getting a harness that fits well.
17. Here’s a good example of removing terminals from a weather-pack connector. You’ll need a very small implement to stick inside to remove the wire. Here, we have the truck alternator plug-in; we removed one of the wires because the LS1 alternator only requires one exciter wire.
18. We looked at the wiring diagram and found the correct hole for our wire. This one is for the alternator, and studying the wiring diagram, we found that it was located on the Red (C2) PCM connector, in slot 15.
19. This Matco brand wire crimper (PN TCT1028) is a lifesaver. It has all the correct crimps, and allows us to breeze through the tedious work of crimping all new connections.
20. After a few sensors, your wiring harness should look similar to this. Go slowly and do one sensor at a time, this will reduce errors and ensure a perfect fit.
21. Here we are attaching the coil power wire to our fuse block; the other end will be attached to power from the battery through our relay. One of fuses will have full time power for the PCM, but the rest will be “key-on.” The other fuses will be used to power the transmission connector, O2 sensors, and the injectors.
22. All of the pink wires from each injector, will be run to our fuse block, each being spliced together. The other wire coming from each injector tells the injector when to fire; all the pink wire does is provide power.
23. You’re probably wondering where the information wire comes from, and you’d be right if you guessed that it came off the PCM connector. Combine that wire with a 12-volt power wire and two-ground wires shown here, and you are business. To wire the OBDII sensor, you’ll need the green wire from the PCM (see diagram) in the upper left position. There are also two ground wires in the two middle positions shown here. Finally, you’ll need a constant power source that comes from the orange wire in the lower right orientation in this image.
24a. After you’ve collected all of your power wires from your injectors, you should have something that looks similar to this. Remember, orange is constant power and pink is “key-on” power.
24b.After you’ve collected all of your power wires from your injectors, you should have something that looks similar to this. Remember, orange is constant power and pink is “key-on” power.
25. After many long hours, we have stealthily run each wire to each connector. The process was repeated for each sensor on the motor. We used Bentley Harris Roundit 2000 braided sleeving that we got from Cableorganizer.com. This stuff is a bit pricey, and puts us over the $100 mark for this project, but it looks totally killer and remember; it’s the little details that really make a car stand out.