Wiring Harness Issue

[pjmia96]

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 --

OK, I have printed the necessary pages for everything for the plugs on both trucks except the HVAC plug, I will worry about that one after I see the truck run.

It appears everything on the 96' 23 pin plug C200 will connect to the 99' C200 plug A-S which is great. I will need to figure out what to do with the additional pins "T,U,V,W" from the 99 trucks harness as I do not have a place for them to connect.

I also see that everything from the 10 pin plug C204 on both trucks will connect without issue. Also good!

I have hope!

 

[1998_K1500_Sub]

I see, if I was to use the ECU from the 99 would I need to get it reprogrammed for my trucks Vin #?

Is it subject to emissions testing? If yes, then “Yes”, the testing people may / will discover the disparity.

Otherwise, it’s the only computer on the entire vehicle, so there’s no other machine to complain that the VIN has changed.

 

[pjmia96]

I made a mistake in my previous post, C204 is not the right plug for the smaller 10 pin plug. The colors do not match with the letters. I will find the right one from the book and report back.

Also, to answer 1998_k15_subs question, the vehicle is not subject to emissions testing.

 

[pjmia96]

OK, this plug has really thrown me a curve ball. I snipped off the connector from my original 96 harness. Pins A and F are not the colors indicated in the service manual, also they change even more going from one plug end to another. All other plugs match up fine,

I am stumped..

 

[pjmia96]

Also, both computers have a service # of 16216588

 

[dilerin]

I would have both wire diagrams available, depin the plugs on your old engine . Depin the plugs on new engine. Repin the old plugs into the new engine harness.
You need to realize, we can't see what your doing. Pretend your describing your problem to your blind friend. And if you're asked for clarification, and get twisted, well you know what happens.

The question actually seems to be fairly straightforward without complication. Curious to know why seemingly all correspondents would assume anything other than a diesel to diesel swap. What did he say that suggests that?
It's an interesting question to which I hope he gets an answer. If an answer is available this is the place to get it. I have received some invaluable info on this forum for which I am grateful.

 

[smdk2500]

Just thinking where does the passlock/vats wireing go? The 99 harness will have it but not the 96. That might be your issues with the wires.

 

[99xcss4]

Just thinking where does the passlock/vats wireing go? The 99 harness will have it but not the 96. That might be your issues with the wires.

this could be a problem you do not want passlock/passkey/vats even though booth of your pcms have the same service numbers the 99 one will need tuned th remove the security from it

 

[GoToGuy]

The question actually seems to be fairly straightforward without complication. Curious to know why seemingly all correspondents would assume anything other than a diesel to diesel swap. What did he say that suggests that?
It's an interesting question to which I hope he gets an answer. If an answer is available this is the place to get it. I have received some invaluable info on this forum for which I am grateful.

It's not always what you say, that promt a question, there is what you don't say, or overlook as you have the complete picture, whereas we only SEE what you tell. It's a two way street. People have jobs, families, their volunteers, and your free to do as you please.
Matching the color of wiring is not the priority, using the diagrams the color is identify the circuit, example 99 reference voltage TPS no 1 = grey. 96 reference voltage TPS no 1 = red/white. Same circuit has a change.
That's why you were advised to have both wiring diagrams, matching the circuits and repin .

 

[dilerin]

It's not always what you say, that promt a question, there is what you don't say, or overlook as you have the complete picture, whereas we only SEE what you tell. It's a two way street. People have jobs, families, their volunteers, and your free to do as you please.
Matching the color of wiring is not the priority, using the diagrams the color is identify the circuit, example 99 reference voltage TPS no 1 = grey. 96 reference voltage TPS no 1 = red/white. Same circuit has a change.
That's why you were advised to have both wiring diagrams, matching the circuits and repin .

Thanks for your voluntary participation in this forum. I'm not the one, by the way, who asked the question. I merely commented on reader reaction. But your technical advice was Awesome. Your flight into Life's philosophy? Not so much.