How To Video, LSx Wiring Swap Harness, 99-02 Truck Harness: 4 Wire Hookup

[matthew20061]

Here's a pretty good video a friend and me made about doing my wiring harness for my 55' LS 5.3L swap that I'm currently working on. It shows how to disassemble the 1999-2002 Chevy/GMC 4.8L 5.3L and 6.0L truck wiring harness, how to remove the unneeded wires for certain things, redo the grounds, and finally convert it to a 4 wire hookup and package it back into a nice harness.

Part 1:

YouTube - How To: 4 Wire LS Wiring Harness...

Part 2:

YouTube - How To: 4 Wire LS Wiring Harness...

Part 3:

YouTube - How To: 4 Wire LS Wiring Harness...

[harnalien]

Awesome, thanks!!
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[usmcchevy]

Nice work!

[clinebarger]

Originally Posted by matthew20061

Here's a pretty good video a friend and me made about doing my wiring harness for my 55' LS 5.3L swap that I'm currently working on. It shows how to disassemble the 1999-2002 Chevy/GMC 4.8L 5.3L and 6.0L truck wiring harness, how to remove the unneeded wires for certain things, redo the grounds, and finally convert it to a 4 wire hookup and package it back into a nice harness.

Why are you running all the ignition hots together? At least fuse the PCM ignition feeds separately with a 10 amp fuse, same with the battery hot feeds to the PCM.

[matthew20061]

Originally Posted by clinebarger

Why are you running all the ignition hots together? At least fuse the PCM ignition feeds separately with a 10 amp fuse, same with the battery hot feeds to the PCM.

What's wrong with running all the switched ignition wires together, they all do the same thing. It WILL have a fuse block that the main ignition on/off will run though and that the battery constant power wire will run though as well.

[clinebarger]

Originally Posted by matthew20061

What's wrong with running all the switched ignition wires together, they all do the same thing. It WILL have a fuse block that the main ignition on/off will run though and that the battery constant power wire will run though as well.

The pcm feeds cant take more than 10-15 amps from a direct short to ground, Running the PCM,(8)Coils,(2)O2 heaters,(8)Injectors,& a MAF sensor on the same fuse is asking for trouble. What AMP fuse are you planning on using?

[paisaloco67]

NOT really the proper way to do it, why dont you show us something new or helpful and not just following what other websites recommend so you can get famous on you tube.

[matthew20061]

Originally Posted by paisaloco67

NOT really the proper way to do it, why dont you show us something new or helpful and not just following what other websites recommend so you can get famous on you tube.

Hey man, not trying to get famous just having fun with video editing. The reason I made the videos was to show people what was exactly involved in redoing a harness. As far as I know I have never seen any videos that show much about these harnesses and how to work with them. I now realize that we did do some things wrong and I should have separated out my positive wires so they can be fused separately as clinebarger pointed out. This was the first harness I did with all the wires together. Other than that what the heck did I do wrong? I've done a couple of these harnesses and never had a single problem.

[Hart_Rod]

Outstanding work and thanks for sharing!

[Notch1988]

I thought the videos were fantastic.

[87chevy.com]

man, everyone does things different... i will pray for your when you have a wire grimlin... all of those splices is also asking for problems. If you were relocating the harness, why not just swap the wires from injectors and coils on the passenger side to the drivers side and vice versa.. the wire color wont be the same but you can make your own notes to the diagram for reference...
otherwise nice job for taking time to make a video .
clint

[CamaroChris]

Thanks for taking the time to do this. I did not know the pins could be pulled out like that. What I want to know Is on a 99-02 pcm what wires would you use to have the PCM control the electric fans I want to use.

[matthew20061]

Originally Posted by CamaroChris

Thanks for taking the time to do this. I did not know the pins could be pulled out like that. What I want to know Is on a 99-02 pcm what wires would you use to have the PCM control the electric fans I want to use.

Look at the wiring diagram on LT1swap.com and see which wire is the fan 1 turn on or fan 2 turn on. On the 99-02 PCM sometimes only one of the pins is controllable so you would have to play around with it.

[C10CORIE]

Cool Vids and thanks for sharing...........I'm a visual kinda guy so pics or vids really helps me.

[CamaroChris]

Ok now for my second question. I am running A/C with my swap. There are a few wires for the A/C out of the PCM. PIN 17, 43 0n red connector. do I remove these? I remember reading in I think Glocks build? that he just hooked the factory wiring from the factory A/C compressor to the 6.0 compressor? He said that some people were frying the A/C system by trying to use the PCM wires. Is this correct? I went digging and cant find where I read that.

[matthew20061]

Originally Posted by CamaroChris

Ok now for my second question. I am running A/C with my swap. There are a few wires for the A/C out of the PCM. PIN 17, 43 0n red connector. do I remove these? I remember reading in I think Glocks build? that he just hooked the factory wiring from the factory A/C compressor to the 6.0 compressor? He said that some people were frying the A/C system by trying to use the PCM wires. Is this correct? I went digging and cant find where I read that.

Sorry no advise on the A/C system I justed deleted those wires if I remeber correctly.

[shortbed70]

Nice
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[mcbassin]

Very nice video. Thank you for taking the time to make the series. I was just thinking you guys made it look super easy. Here is what I am starting with and didn't have a clue where to start.

So after reading on which wires "should" be on seperate circuits? I don't mind adding a fuse box.

[matthew20061]

Originally Posted by mcbassin

Very nice video. Thank you for taking the time to make the series. I was just thinking you guys made it look super easy. Here is what I am starting with and didn't have a clue where to start.

So after reading on which wires "should" be on seperate circuits? I don't mind adding a fuse box.

Thanks! Ya about the power wires, you will end up with a ton of 12V+ Pink wires, on my hack I connected them all to one big wire and fused it (not the right way). What I would do next time is separate them out and figure out which ones power all the coils, maf, o2's and such. Then make each on its own fuse of split them up so coils and maf are on one and o2's and other things are on the other. Once you get the harness stripped down it starts to get pretty simple and you just need to trace wires and look at the diagrams.

[DirtyLarry]

Nice work but personally, the last thing on earth I would use on any LSX swap would be a factory GM takeout harness. The factory hecho en Mexico GM harnesses supplied by Delphi have plenty of wiring issues of their own (poor crimps, unprotected splices, etc ) even before molesting them. The 1999-2002 donor truck harnesses are getting old now where the wires are stiff and weather pack connectors are getting brittle from engine heat. If you live in the salt belt you can count on corrosion issues too. I wouldn’t touch one! A quality aftermarket harness from one of many suppliers would be the best $500 you could spend on a LSX swap.

But hey, if it works for you then all is good. Great job on the video though! Maybe someday you guys can move to Nashville and be hosts on TRUCKS! or HorsePower TV or one of those other car shows.

[mcbassin]

Originally Posted by matthew20061

Thanks! Ya about the power wires, you will end up with a ton of 12V+ Pink wires, on my hack I connected them all to one big wire and fused it (not the right way). What I would do next time is separate them out and figure out which ones power all the coils, maf, o2's and such. Then make each on its own fuse of split them up so coils and maf are on one and o2's and other things are on the other. Once you get the harness stripped down it starts to get pretty simple and you just need to trace wires and look at the diagrams.

Thanks Matthew. Exactly how did you know what wires to keep and what wires to discard. I have looked at the LT1 link, not sure where to find the road map? I obviously have an 03 up since it has a DBW throttle body. I don't know where to start cutting. Keep in mind my harness is complete all the way to the firewall, even has the fuse box. Not sure what should or should not be kept for a stand alone install?

Also, I saw that you used an LS1 intake with truck accessaries on your vid. Did you have to modify the intake or change the water pump? I seem to recall there are some subtle differences that cause interference.

[Thealien]

Mcbassin start with this page and as you scroll down and he color codes what should be kept and what should/can be removed.

http://www.lt1swap.com/2000harness.htm

Also on that page you can click on the year of the harness and it shows what each PCM pin does/where it goes to.

Here is another way he shows color coded what needs to stay and what needs to go

http://www.lt1swap.com/2004vortec_pcm.htm

[mcbassin]

Originally Posted by Thealien

Mcbassin start with this page and as you scroll down and he color codes what should be kept and what should/can be removed.

http://www.lt1swap.com/2000harness.htm

Also on that page you can click on the year of the harness and it shows what each PCM pin does/where it goes to.

Here is another way he shows color coded what needs to stay and what needs to go

http://www.lt1swap.com/2004vortec_pcm.htm

Thanks Thealien! I think I have a sense of direction now. The only thing that stuck out to me so far; if we are using the stock LS A/C compressor will we need to keep any wires? for cycling the clutch? I am using a Vintage Air kit. Not sure if it has a sensor for low freon or what?

[CamaroChris]

Originally Posted by DirtyLarry

Nice work but personally, the last thing on earth I would use on any LSX swap would be a factory GM takeout harness. The factory hecho en Mexico GM harnesses supplied by Delphi have plenty of wiring issues of their own (poor crimps, unprotected splices, etc ) even before molesting them. The 1999-2002 donor truck harnesses are getting old now where the wires are stiff and weather pack connectors are getting brittle from engine heat. If you live in the salt belt you can count on corrosion issues too. I wouldn’t touch one! A quality aftermarket harness from one of many suppliers would be the best $500 you could spend on a LSX swap.

But hey, if it works for you then all is good.

Where do you think the suppliers get their harnesses? you send them your factory harness and they do what these guys did in the video. the only difference is that you save 500$ only harness that new is from painless and IMO way too expensive. or you can get a bran new harness from GM for 2700$ the wires in my 2000 harness with 200k on it look and feel bran new.

[DirtyLarry]

Originally Posted by CamaroChris

Where do you think the suppliers get their harnesses? you send them your factory harness and they do what these guys did in the video. the only difference is that you save 500$ only harness that new is from painless and IMO way too expensive. or you can get a bran new harness from GM for 2700$ the wires in my 2000 harness with 200k on it look and feel bran new.

Negative. I send Howell Engine Development $500 and they build me a new harness with new wire, new terminals, new J1 and J2 connectors, new weather pack connectors, new relays, new split loom, ECM tuned to whatever requirements are, etc. And they do it all with new OEM Delphi components. The difference is the small custom harness suppliers like Howell take care in building the harnesses unlike the underpaid 13 year old kid in Mexico that built the production vehicle harness plus you don't need to clutter up your engine bay with the UBEC.

I work with new vehicles every day. These days hard part failures are pretty rare. Where the problems are always found is in the wiring where some lazy assembler at Delphi did a pizz poor crimp or splice. Factory wiring harnesses are terrible. The components are good….the assembly process is terrible.

There is no way a 10 year old – 200K harness looks and feels brand new after that many engine bay hot soaks. I am not buying that one. Heck, you can’t hardly pull a weather pack connector off of a 5 year old vehicle without breaking off the locking tang.

Somebody is going to be able to whittle this…


To this? ..... I don't think so.



This is not to blow holes in Matt's work. They did a great job. I just would not use a factory take out harness if it were me. If you can spare another $500-$700 get a new harness. You won't regret it!