1999 5.3 wiring harness

[ivorton74]

So I just got done reading about making a stand alone harness on lt1swap.com. There was a step by step article with pics and its seems kinda simple but looks can be deceiving. Have any of you guys done your harness yourselves? How long did it take u and did u have any problems after u got done? I kinda want to try it but im scared to. The last thing I want to do is mess something up and having to buy a new harness.

[softballnrd27]

It was actually very easy but it takes alot of time. I re-did mine 3 different times bc I just wasn't happy with the way it was routed or how it looked. In the end I just cut all the sensors w/2-3" of wire and soldered on new wire and pins so I could route it the way I wanted to. I used all black wire so the only drawback is it might take a little longer to find a bad wire. I am going to change over to the Holley Dominator ECU later on so I can have plenty of aux in/out when I put a turbo on the 5.3.

[72c10suburban]

I've got mine thinned out but I'm still waiting to get my engine and tranny back together to figure out where the harness needs to lay to run the fuse box. It's not too bad so far just time consuming. The diagram I started using for the under hood fuse box was wrong so I ended up tracing all of the power wires to the injectors etc separately plus my engine was flex fuel so that added a couple hot wires also. So far so good. Mines not running yet so I can't say if it would have been money well spent to have it done.

[Crash_OK]

I didn't find it that hard, I enjoyed doing it actually. Took me about 7 hours. I did not reroute any of the wires, I left them routed the same as the factory. I did lengthen some of the wires (power, tach, speed, etc..). I am about to start on a second harness for a engine swap in my Land Cruiser.

Good luck with your swap.

[whitels1]

The harness - It took me about 7-8 hours to separate / label everything and to get down to the injector / coil pack harness. I then figured out where my pcm would be mounted and started routing, it helps to have the engine in place or at least a mock up. I ran mine inside the cab and did not have the lengthen the harness.

Now for the fuses / relays this is the part that takes time and planning. Everybody has a different way of doing things. I started out with making a fuse / relay / breaker box you can see it in my build thread http://67-72chevytrucks.com/vboard/s...d.php?t=532351 don't forget the rectifier diodes for the fans and fuel pump relays. Before I wired anything in the truck I used a program and made a schematic so that I would know where everything was wired and keep me on track. When done make sure you have good grounds to your frame, body, radiator support, block and left / right head. Use at least a 4ga wire from the alternator to battery to ensure you have enough current to power everything. Take it one circuit at a time, it took me a week or more to wire everything.

[Angryman117]

Was not that hard, took me about 4-5 hours. Brought my laptop out the the garage and made sure to to label every wire except the ones I did not need.

[ivorton74]

Did anyone follow the article on the lt1 site to do ur harness?

[littlevictories]

currently in process. using the brendan's lt1swap.com guide on facebook.
seems pretty easy so far, just tedious.
echo the enjoyability statement. kinda fun, but you gotta be in the right headspace.
not a job for when you are real tired or cranky.

got my fuse block and obd2 port in hand monday, hope to button it up early next week.

i think i'm just gonna route it stock-ish. PCM on the driver's fender, fuseblock next to it.
probably move the MAF wires to the even-cylinder injectors and call er good. move my battery over from the passenger side too. make it easy on myself.

my thought is learn on this one, get fancy on the next one

[ivorton74]

I looked at the harness awhile back and i thought those are really intimidating...maybe i should just try it...i was goin to have to pay my buddy to do it for me...ill save some cash

[chuckmc8]

The first swap I did, I bought the harness and didn't know what any of the unfamiliar (to the old small block components) were. The next I did the harness myself. Useful tip: Take the time before you begin the harness modification to learn those unfamiliar components of the LS based engine and what they do. When you have this understanding before you start on the harness, you have a better concept of what you are doing when you are pulling wires out of the loom. Chilton manual with pics is one way to learn that info. The instructions on Brendan's facebook page are spot on and easy to follow, but you do have to pay attention to what you are doing.

[JDizzle]

Originally Posted by chuckmc8

The instructions on Brendan's facebook page are spot on and easy to follow, but you do have to pay attention to what you are doing.

Could you please provide a link to the facebook instructions you're talking about? I found LT1 swap on facebook but didn't see anything C10 specific.

[ivorton74]

Originally Posted by JDizzle

Could you please provide a link to the facebook instructions you're talking about? I found LT1 swap on facebook but didn't see anything C10 specific.

https://www.facebook.com/media/set/?...5211824&type=3

[Blackpony]

It's actually really easy just takes time. I would suggest stripping all the loom off first. Then go through and remove all the un-necessary wires. Once you have just the wires and connectors you want, take the harness and plug everything into the engine preferably on a stand, then you can decide how you want to route the bundle of wires. I ended up shortening a bunch of wires and having the main loom go across the back side towards the driver side and putting my fuses, relays, ECM etc on the driver side liner..

Here is how my set looks finished in the bench.



Here is my sloppy mess once I was pretty much done. Not at all happy with it but it's functional. I plan to build a new harness very soon using a fuse/relay panel I bought from bussman and route it in the cab behind the dash.

[ivorton74]

Well I just got done watching some videos on youtube of some guy doing his harness and holy smokes that's a lotta wires....i'd be so confused and petrified man. there's 7 videos in all from this guy and he looks like he knows what he's doin...he been following the lt1 write up as well...

Part 2 -- LSX 5.3L / 4L60E wiring harness LS1...

[BR3W CITY]

80 pinouts per ecm plug=160 pins -5ish unused each side is ~150 wires. At an average of 4ft per lead (guess based on my van harness), that means you have roughly 600ft + of wire to run. lol