I may end up doing that. I appreciate the idea!
Wiring Harness Issue
- Thread starter pjmia96
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I may end up doing that. I appreciate the idea!
99xcss4
frank'n (truburban) K-2500
it is easy get the electrical diagram for a 96 and get one for a 99 and do some de-pining and re-pining or go and pull the cab harness out of the truck you got your donor parts from
99xcss4
frank'n (truburban) K-2500
was replying at the same time just a heads up for it is a lot of work to pull the dash and then the harness I am doing it on a 94 went from a diesel to gas need to swap engine harness transmission harness t-case harness dash harness and the harness that has the taillights in it because it also has the fuel pump wiring in it
This is my first ever engine swap. Maybe I should have called it an engine replacement. The transmission was also slipping so that came from the donor truck as well.
I have a couple of different wiring diagrams but I can't seem to find these particular plugs on the ones I have. I do know the smallest black connector is for the blower motor/HVAC.
Any ideas on where to find a schematic on these connections? By the way nice signature, I'm an AIC fan too!
99xcss4
frank'n (truburban) K-2500
check here in the service manual section https://www.gmt400.com/threads/88-98-service-manuals.43575/ my self I have never de-pined or re-pined any thing before so that is why I said to go and get the rest of the wiring even though it is a lot of work to do so there are people here that know a lot more about this then I do
Thanks Man!!
Greetings Matt,
Now that I have a good grasp of what you are trying to do, thanks to all the contributors in
the GMT400 forum I can guide you to the info you will need to perform your '96 > '99 engine swap.
For what it's worth, the links for the '96 & '99 manuals didn't make the first post of that
Service Manual thread, but other members contributed them in later replies:
Reply #84: '96 GMT400 Service Manual link: '96 FSM
I've downloaded and used this manual to help others. Seems to
work and search fine.
Reply #77: '99 GMT400 Service Manual link: '99 FSM
I happen to own a '99 C2500, and have used the '99 manuals a lot,
the old "Ctrl F" is your friend, and the wiring diagrams are in Vol 4.
And to give you a taste of what you will have to work with, there are 3 attachments to this:
* 1st attachment: '96 FSM Diesel PCM Component Location
From that diagram, I figured out that C200 is the name of the connector in question.
* 2nd attachment: Check out the '96 C200 16-pin pinout diagram (for Diesel)
* 3rd attachment: Here's the '99 C200 23-pin pinout diagram (for Diesel)
If I were in your shoes, I would download both, print out the relevant pages,
create a detailed punchlist/checklist, and only then migrate from one harness
to the other. NOTE: I'm not fully up on the Diesel PCMs. Are they identical
part numbers, or different? The reason I ask is that IF they are different you
need to decide whether your truck is going to remain true to the '96 Manual
and migrate with that in mind. Or are you going to move your truck to the '99
Manual? If I'm not mistaken, starting in '98 the VCM (and PCM?) monitored the
fuel system more. (In order to better implement evaporative emissions testing
as part of the more stringent EPA requirements? I could be on thin ice here. :0)
The point is that you need to answer this first, and then plan your wiring harness
transplant accordingly. (I'd think that you would want to remain in '96-land, but
by doing so you need to chase down the implementation details so that you know
what *must* be implemented, and what '99-era wiring is not relevant and can be
dead-ended.)
Q: As a baseline, were there -0- codes and the SES light was out? Or was there
a noise floor of a handful of persistent codes and a solid SES light prior to the swap?
The reason I ask is that I'm hoping the former, so that any 'false' errors from the
wiring swap will stand out and be easier to sort out, as opposed to trying to figure
out if there's leftover issues in the engine bay -or- a wiring harness merge mistake...
or even an issue with the new powerplant/transmission?
Hope you find this helpful. And welcome to the GMT400 forum!
Best of luck with your project to keep this truck on the road.
Cheers --
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First off, Road Trip you are a lifesaver. I really appreciate your help. I have not compared the part numbers written on the PCM's, but can do so in the morning. I do plan to stay with the 96 PCM and just use the harness from the 99 donor truck. My 96 PCM is a re-manufactured unit as well that was replaced not too long ago. The truck had no codes prior to tear down and SES was out. One thing I know is the PCM part # is the same on RockAuto for a 96 & 99, not sure if that is useful info for you. Thanks so much, I will look into this more tomorrow.
Matt
I think your better option is to use the 99 ECU, you're taking a gamble by assuming they're interchangeable as-is.
Even if the hardware happened to be the same, differences may exist in, at least,
- the firmware,
- the ECU's pin assignment / pin function, and
- the "tune" (aka parameter configuration)
Any difference, however modest, could be a rabbit hole that you'll spend days, even years, trying to find your way out of.
I know a guy who swapped a V8 engine into a V6 Dodge pickup and thought he knew what he was doing. Yeah, well, after the swap the V8 engine wouldn't run... indeed, the V8 engine didn't run for over a year for reasons unknown. A number of "knowledgeable" people tried to help, without success. The problem EVENTUALLY was determined to be combination of (a) an incorrect oil pressure sensor and (b) a poor ECU ground connection. How simple is that?
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I see, if I was to use the ECU from the 99 would I need to get it reprogrammed for my trucks Vin #?
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