96 C3500 RCLB aka Stumpy

[Stumpy]

Forgot to mention, I shipped out the parts truck PCM to Black Bear, to get tuned, and run the 4L80e in my truck. Hoping it all works out, now I need to figure out how to wire it up.

 

[Stumpy]

A little overwhelmed here.

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I'm thinking I need to de-pin the pcm connectors, marking each one where it went. I believe this will be the way to get the wires I need out. Does that sound right?

Concerned already about some of the places where wires are joined together. Obviously apprehensive to cut anything, but it's clear, there will be some wires that will need to be cut. That's the scary part.

Got to get some maskng tape or similar to mark all the wires, so I can write down, where it went, then I can really start getting nervous.

 

[Orpedcrow]

When I de-loom a harness, I like to put a snug zip tie at the intersection of the “branches” to mark where they go for fitments sake. I also spread the wires at each plug and take a picture of both sides making sure there’s a clear image of the orientation and location of each wire. Good luck!

 

[GrimsterGMC]

When I de-loom a harness, I like to put a snug zip tie at the intersection of the “branches” to mark where they go for fitments sake. I also spread the wires at each plug and take a picture of both sides making sure there’s a clear image of the orientation and location of each wire. Good luck!

Good points, and the most useful feature of a cell phone is the camera. You can take as many pictures as you want without having to pay good money to get them developed after every 24. Remember those days.

 

[Stumpy]

Thanks for the tips. I'll be taking it slow for sure.

Also, something odd I forgot to mention before. The plug in the middle of that pic, just above the screw driver and knife, has what looks like two black wires coming out of it. Once the loom was removed, it's actually the same wire, about 4 feet long, looped back around. That seems like a lot of trouble, for what appears to be a jumper wire. Weird.

 

[HotWheelsBurban]

Good points, and the most useful feature of a cell phone is the camera. You can take as many pictures as you want without having to pay good money to get them developed after every 24. Remember those days.

Yeah I remember trying to find a good place to get film development done. I used to shoot pics of my friends' bands when they played in Houston or Austin, and you can burn through a 24 exposure roll real quick! I would get 36s when I could, but of course they were half again as much to get developed. I liked going to digital because I could get prints when needed at work cheaply, and edit them if needed. And make photo CDs for my buddies too.....

 

[Road Trip]

A little overwhelmed here.

You must be registered for see images attach

I'm thinking I need to de-pin the pcm connectors, marking each one where it went. I believe this will be the way to get the wires I need out. Does that sound right?

Concerned already about some of the places where wires are joined together. Obviously apprehensive to cut anything, but it's clear, there will be some wires that will need to be cut. That's the scary part.

Got to get some maskng tape or similar to mark all the wires, so I can write down, where it went, then I can really start getting nervous.

From personal experience, when working at the "whole harness" level the more
you do *at this point* to familiarize yourself with the harness AND the relevant wiring
diagrams the more that this becomes a straightforward task requiring attention to detail vs.
one of the scariest things you can do to something you like enough to go through this
level of effort. :0)

If I were doing this, here is what I would absolutely do:

1) PROBLEM: One of my first 'whole harness' swaps I tagged every wire with
masking tape, wrote a unique (incrementing) number on each, and
wrote that down on a separate sheet of paper what pin of
what connector each end came from.

It was great when I did it. And then the harness got stuffed in
the passenger compartment of the donor vehicle (for safe keeping)
while the new vehicle was being worked on.

Guess what? Thanks to the excess humidity in the closed up
passenger compartment, everything I had so carefully marked
ended up bleeding/fading to the point where we were using
magnifying glasses and having to (attempt to) cross-reference
to the (inferior, non-OEM) wiring diagram we had to work with.

To be perfectly candid, it s*cked so bad I still get a headache
just thinking about it. I finally got it all sorted out, but there
were many tears of frustration shed over this. :0)

SOLUTION: I still mark *every* wire, but now whenever I do
this I have learned to place some clear Scotch tape over
*anything* I write. Even over 'permanent' marker. 6 days,
6 weeks, or 6 months later you will still be able to read
your writing like Day 1. If the wiring harness has to be
stored temporarily, bonus points for putting it all gently into a
30 gallon plastic bag with a handful of small desiccant bags,
tie it off, and place that in a cool, dry storage area.

2) PROBLEM: Once the harness is transferred/installed into
the new vehicle and the inevitable electrical troubleshooting
has to be performed, *now* you are also trying to learn
how YOUR wires travel through the wiring diagram
across multiple pages.

Further complicating this issue is that very few wiring
diagrams are perfect/completely match what you are
actually working with. It will be a pain now to figure it out,
but it's better to do this now before you need to actually trust
the documentation to troubleshoot with. (ie: Find out now about
a running change during production made *after* your edition
of the Service Manual was published, etc.)

SOLUTION: Either use a spreadsheet (new school) or buy
yourself whatever general ledger is the easiest for you to follow
(old school LINK) ...as you disconnect each wire in your physical
harness find it in the Service Manual's wiring diagram, and document
what page/pages where this wire is shown. Bonus points for
ohming each wire & writing that down as well. (Especially if there's
corrosion leading back from the pin to underneath the insulation.)

By doing all this, you will prove to yourself that the wiring harness documentation
matches your physical harness. And by writing this all down, this
will shorten the time it takes to navigate through the wiring diagrams &
take 90% of the frustration out of the troubleshooting session.

NOTE: It's so much easier to troubleshoot a wiring harness that you actually
believe in (both books & physical harness) than one that's just a multi-colored
guessing game.

****

In a previous life I used to be tasked with hot-rodding our older military
fighters with new/improved Avionics systems. And the first jet was always
a crazy challenge, and took way longer than it was supposed to. But as
we went through the fleet, we would take the lessons learned & also get
really familiar with the relevant wiring diagrams...so that by the end of our
fleet we would actually take less time than documented and be able to make
all the changes and have the follow-on Ops Checks pass with no wiring
harness troubleshooting.

Why do I tell you this? Because you probably only get to do this once (instead
of several/many) ...so it's never as comfortable as it could be -- so don't beat
yourself up when it takes longer than you ever thought possible.

I know that the above sounds like a *lot* of extra work, and might be for those
who've spent a career troubleshooting automotive wiring harnesses. I don't know
about you, but for me fear of failure motivates me to cover the bases like few other
things can. :0)

Seriously, prove your physical harness against your wiring diagram, cross-reference
all this on a general ledger...and after you are done with this project you will never
look at an electrical issue in a vehicle the same way again.

For what it's worth...

PS - IF you don't have time to do every single wire, then at least do All/Only the wires
that are critical paths to success. (For example: Document *every* wire needed to get the engine
& transmission to run, and don't bother with the heated seats, electric windows, etc.) This way you
can best tailor the documentation process according to your personal threshold of pain.

 

[Stumpy]

Thanks Road Trip. This is by far the most complicated bit of automotive electrical I've tackled. Will be a learning experience for sure.

 

[Road Trip]

Thanks Road Trip. This is by far the most complicated bit of automotive electrical I've tackled. Will be a learning experience for sure.

Stumpy,

I actually have a photo to prove that I don't have sympathy for your situation...I have empathy. :0)
(See attached.)

Given what I've observed in this forum to date I think that there is definitely the critical mass of knowledge
and experience required to see this through to a successful conclusion.

One wire at a time. And the more confidence you have in *your* documentation, the less fear for all
involved. (And I say this from the perspective of coming in to help someone troubleshoot after it's all
been modified...and they can't tell me what changes they made because they didn't write ANY of it down.)

10x harder to sort it out that way. And they are usually in a hurry because they need to drive it to work.
And they don't have the money to buy a short term beater for commuting duty. Needless pressure
& complexity = zero fun to be had. :-(

But I'm not getting that vibe here -- Yay!

 

[bluex]

Thanks for the tips. I'll be taking it slow for sure.

Also, something odd I forgot to mention before. The plug in the middle of that pic, just above the screw driver and knife, has what looks like two black wires coming out of it. Once the loom was removed, it's actually the same wire, about 4 feet long, looped back around. That seems like a lot of trouble, for what appears to be a jumper wire. Weird.

Idk if you watch junkyard Dave on you tube, he's building a badass awd wide body hellcat charger wagon. He's wired the whole car integrating Durango, charger an challenger stuff. I've lost count of the amount of wires he's rerouted an shortened but it was enough to wire another whole car I bet. I'm normally not to scared of wiring, it isn't my favorite task but I'm fairly decent at it. Idk that I would have tried what hes done.

Maybe I missed it but why not just swap the entire engine side harness from the donor to add in the trans wiring?