Allright, I have read over every one of pockets' wiring guides and reallllly appreciate how well it was all documented, and laid out for the rest of us to use. I have been working on prepping mine today, and have a few wires I cant find out what they do.

Here is my harness as of right now:



The top of the picture, from left to right the wires are:
-2 Thick Red wires: Starter
-Thin Tan wire: Oil pressure sender
-1 Blue and 1 Green wire: B/U Lights (Manual)
-Thin Brown wire: Generator (Alternator)
-Thick Pink wire: Ignition
-Thin Purple wire: TCC (But The harness is for a Manual?)
-The Tan/white wire underneath the IGN wire is the fuel control wire

Bottom of the picture, left to right:
-1 Green, 1 Grey, and 1 Pink wire: Windshield Wiper Motor
with a Red and Blue wire coming off of that connector: ???
-Thick Purple wire: Starter Interlock
-Thin Pink/Black wire: Cold start/Emissions
-Thin Dark green wire: Coolant temperature sender
-Thin Purple wire: Accidently cut from wiper motor harness (will be re-attached)
-Thin White wire: Tachometer
-Thin Yellow wire: ???
-Thin Red wire: ???

The Yellow wire appears to be in position "D4", but according to the '88 C100 wiring diagram, there shouldn't be a wire there. The Red wire appears to be in position "F6", with the same story. What are these wires supposed to do?

Also, where do the 2 wires (Blue and Red) that come off of the large wiper motor connector go?

I wrote down as many 3rd gen and LT1 wiring diagrams that I could in a binder, but I see many things that don't add up, and I cant figure them out by myself.

I have been using these following guides:
http://www.lt1swap.com/all_lt1.htm
https://www.thirdgen.org/forums/ltx-...p-3rd-gen.html
https://www.thirdgen.org/forums/ltx-...rt-finish.html

Oh, it may be useful to add that I am swapping an LT1/T56 from a 1994 Z28, into a 1988 IROC that HAD a 305TBI/T5.

Thanks!

 

Up..

 

not that its much help, but i ran into a similar issue when reworking my harness. i ended up grabbing the GM repair manual for my specific vehicle from another member to trace down the wiring I couldn't figure out. Might want to see if someone you know has access to alldata

 

D4 is Yellow and on the schematics it lists is as 'Not Used.' Are you sure that is F6? I have a Red wire in E6, which is for 'Fuel Control.' The schematics that I am using are for an '89. I am trying to figure out the
Blue and Red wires, also.

 

Yel is half of the old VSS wiring feeding the buffer box
http://www.austinthirdgen.org/mkport...SS_V8_vinE.jpg

Red is the fuel pump relay prime at the ALDL. Older cars moved it there to speed diagnosis at one place. Later cars (and some earlier) lets the prime wire separate in the engine bay

Neither are reused

Red/blue from the wiper is washer tank pump

 

Thanks Pocket, always helpful!!

 

More questions:

Do I even need a C207 to make this work?

I see that things like: Coolant fan, Emissions, cold start, Passkey, Idle speed control, injectors, Tachometer, MAF....

But the Tach goes through the C100, MAF goes through the LT1 ECM, I am using an aftermarket Fan controller, no need for coldstart, no emissions, car is an 88 so no VATS (Passkey), etc....

Can I just run a little fuse box in the engine compartment with a single power wire going to it, and power the "ECM BAT fuse #4", and "ECM IGN fuse #5" to it, and it would work just fine?

 

while i've been able to knock out about half of my C207 (all pcm fuses are going to a seperate harness due to the carbed setup's lack of fuses under the dash), it's gotta stay.

on mine for the 87 TA, I need
C - ses light
L - power to fuel pump (oddball year)
M - ground (may be able to get rid of, but its not hard to do a ring terminal for good measure)
N - park/neutral signal
P - TCC (I think)

to keep things easier, don't get rid of the connector. diagnostics are not easy as-is, don't make your life more difficult

 

I didnt cut the connector from the under-dash harness, I plan on just leaving it there, but unplugged.

I dont mind not using the under-dash fuse block for INJ fuses, and such. In fact, I would rather have a seperate block under the hood, as I find it more convenient, anyway.

Basically, the only thing I "need" from that is:
C - SES
L - Mine runs through C100
M - Pretty sure it doesnt matter.
N - ?? I assume its an automatic starter enable thing
P - Again, automatic

I am running a T56.

Do you know anything about using the LT1 Fusebox under the hood? I have it but it has ALOT, and I mean ALOT of wiring connected and I dont know where to begin. I was planning on using that to power the Injectors, and whatever else needs to be fused.

 

For my underhood fuse box, i think I'm going to have about 6-8 fuses
ecm
fuel pump
inj 1
inj 2
O2
coil 1
coil 2
maf

relays will be fuel pump, fan 1, fan 2, and main

I opted to build my own fuse box to keep it as small as I could reasonably do following the instructions here:

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

 

Ive been searching and read about 15-20 threads concerning the use of the LT1 under-hood fuseblock, and many have done it, but dont provide much info on "how", ya know...

Worst case scenario, I get an aftermarket universal fuse block like that and wire it up myself, but I already have the 4th gen unit, and really want to use it.

I didnt realize there would be so many fuses for the under-hood stuff. I will have to go over my wiring diagrams that I wrote down to see if it matches yours.

Are you talking about an LT1 situation, or an LS type engine? I am doing an LT1.

Thanks

 

I'm going LS1, so you may not have quite as many. your notes probably are more complete than mine for that setup, but it would probably be a good idea to see if you can find a shot of the fuse panel (if you dont have one already).

 

Allright, I have been working on the LT1 harness a bit today, and I stripped the fuse/relay center of all plugs except for the one that plugs into the engine harness (c100), and hooked up all of the "hot" wires to my distribution center. We'll see how that plays out.

Anyway, here is what I really need help on.. I hooked up all the gauge wires, and the reverse light wires, but the rest have me a little confused..

Heres what I got:
On the C220(White connector):
- Oil level feed: Not used
- Spark Retard Request: ???
- TPS Signal: ???
- Serial Signal: ???
- VSS: Does this hook directly to the VSS wire on the cluster? (4th gen cluster)
- Skip Shift: ???
- Fuel pump Relay control: ???
(The rest I already hooked up)

On the C230(Blue connector):
- SES: Goes through the C207?
- Diagnosis request Signal: ???
- Theft Deterrant (Fuel enable Feed): ???
- A/C Request Signal: Not used
- Power Feed from PCM IGN fuse #2: ???
(The rest are hooked up, allready)

C210(Black connector)
- Crank Starter (Connected to the started relay): ???
- Power feed from ECM BAT fuse #4: ???

Does any wire that is labeled like "Power feed fuse BAT", just ran from a + source, through a fuse? And is any wire that is labeled like "Power feed fuse IGN", just ran from a Keyed + source, through a fuse?

The ones I labeled with "???" are the ones I am stumped on.

Any help is appreciated.

 

Kinda hoping to get this pretty much done tomorrow.

Anyone?

 

Hope that clears things up

 

Thank you!!

But, I no longer have the FP relay wired in, or the fuse near the battery since I prepped the harness. How do I go about hooking the FP relay up, and can I use an external Fuse block for any "Power feed fuse BAT", or "Power feed fuse IGN" ??

 

Also, where does the main (Thick Pink) IGN wire go to, from the 3rd gen c100?

 

 

Its the main IGN wire, but it's unfused. If you reassign all your C207 fuse wires and have a few pieces left that need to be attached, pop and inline fuse and there you go

For carb cars, this is the IGN relay engage wire

 

I am a little confused on what you mean?

I think you mean that if I run out of fused IGN wires through the C207 (Or an external fuse block) , that I should run an inline fuse through that main IGN wire and use that. Do I have to use the main IGN wire?

 

Been trying to figure out the FP relay, I found the connector and here are the wire colors:

A(Tan/Wht): To the Tan/Wht wire on the 3rd gen C100
B(Blk/Wht): Ground
C(Grn/Wht): To "Fuel pump Relay control" on LT1 C220
D(Red): Fuel pump prime connector, where does it go?
E(Orn): + BATT

Is this correct? Where does the red wire connect?

Thanks

 

Prime is a test lead to bypass a possible ECM/PCM fault in the relay system. Add 12v and the pump will prime under all circumstances

Leave it alone or cut it out

 

Allright, cool. I wired it that way, and just ignored the red wire.

Thanks

 

I think I JUST realized something that I didn't know about...

Lets say I wired everything correctly, and everything works, etc.. Will the engine even start? I think now that there is VATS built into the ECM, which wont allow me to start it. How the hell do I go around that? I've read "just bypass VATS in the ECM".... how???

Just when I think I am getting something accomplished, I find this!!

Any help is appreciated.

Can I use this to solve the problem?
http://cgi.ebay.com/ebaymotors/GM-VA...Q5fAccessories

 

Tune it out

That module is an unnecessary piece since youll need a tune anyways

 

I don't understand what your talking about.

How do I "Tune it out"?

What exactly needs to be "Tuned" anyway?

Why can't I just leave it the way it is?

 

You can turn off vats in the pcm. but you need the cable to hook up and the software to tune with.

http://www.tunerpro.net for tuning is a good one.
few more links for ya.

http://www.lt1howto.com/articles/pcmtuning.htm

 

Thanks for the links but I am really not sure why I would even need a tune?

I am using the same exact motor, transmission, wiring, ecm, etc.... that came out of the running 4th gen. What would I need to "tuned" exactly? I really dont have the Equipment, money, knowhow, etc... to do any of that.

But, will that bypass module work that I posted a link to?

 

you can use a .10cent resistor from radio shack. for the factory vats bypass.
Im not sure about the lt1 pcm. n vats.

heres some good info.
http://shbox.com/1/4th_gen_tech2.html#pass_key

I have all the tuning stuff need and cables. id have to dig out lt1 software for re-flashing. the pcm

 

VATS did not start in Camaros until 1989, that isnt my issue. What I have read is that the ECM will only allow the engine to run for three seconds, unless the VATS is bypassed in the ECM. The module in the link I provided has a very simple 3-wire hookup, shouldnt take more than 5 minutes to hook up.

I am not asking how to tune an ECM, or anything like that. I am asking "WHY"?

What is the reason for having to do so? It makes no sense to me. This came out of a running, driving car, its not a new ECM that has to be made to work with my setup or anything like that.

What does a tuning consist of? What is so vital that I could not run it as-is? I don't understand??

Thanks =/

 

I understand how the VATS works through the lock cylinder, but I dont understand why I would need a "tune"?

 

the vats is programmed into the computer. you can have it disabled by someone who has a flash tool, much in the same manner as having the egr tuned out or having the tach reprogrammed. do it in the computer and you dont need to have any other hardware to buy.

 

Yes, this I understand. But he said to program it out of the ECM, that I need a tune *anyway*. Why is this?

If I just get the little chip to remove VATS, is that all I need to do?

 

Any word on this?

Want to place the order soon if thats all I need.

 

I think VATS needs to be tuned out or shut off with a tune because you are not wiring in the LT1 VATS circuit. The vats circuit consists of the VATS module, theft deterrent relay, lock cylinder connections, etc.

Pic of the VATS schematic: http://shbox.com/1/pass_key.jpg

I think what else is trying to be said that programming out and getting a tune are kind of considered to be the same thing. They cost the same, so might as well get a tune with all the bells and whistles, instead of a tune just to shut one thing off.

If you want to wire in all the VATS stuff and throw in a resistor and not get a tune then thats ok too.

I would recommend a tune though because there may be other things you want to change. You may not be running EGR so you would want the EGR trouble codes deactivated so the service engine soon light doesn't come on, you may have different gears so you would want the computer to know your rear axle gear so it will output the correct speed on the speedometer. Plus, with a tune, they can make them gain about 5-10hp over stock

 

How would I go about getting a "tune"? I don't want to send out my ECM or anything like that. Does it get tuned through the ALDL connector?

I have the same gear ratio in my camaro as the camaro it came out of, so thats no big deal. I think the EGR on this motor got broken off, so that may be useful.

 

Download tunercat trial version, buy the tunercat definition file for LT1 for about $20, buy a ALDL cable for $45-90 - depending on if you want to assemble the circuit board on it or not. Buy a tune from madtuner.com or pcm4less's website(i don't know it) for i think $75

It may be cheaper just to send it in the us mail to someone if you only plan on tinkering with the PCM one time.

 

Man, those add up quick. A $20 little module doesnt sound too bad at that price, lol.

I wish I would have known about this whole tuning deal alot sooner. I am hoping someone local can do it for some parts or some $, because I cant see myself using all of that more than once or twice.

Thanks

 

I take back the tune part for $75. You wouldn't need a professional tune if you had the tunercat program, lt1 def file, and the aldl cable. With those three, you could easily uncheck the boxes in the program for VATS, EGR. And may be able to find a deal on a ALDL cable if you search ls1tech.com's classifieds.

 

And this is all done through the ALDL port?

Do you by any chance know of how many wires would be going to that specific plug, would you? I have 2 that should go there.

 

I believe the 2 wires are the enable wire, and serial data wire from the PCM:
http://shbox.com/1/DLC_wiring.jpg

The ALDL cable may require a ground and power wire also.

Also note, 94's use a different connector than 95. However, same wires come from the PCM, just different connectors. So, if you had a ALDL cable for a different year, could just cut off the ends and tie the wires together temporarily.

 

93-94 LT1s used the OBI ALDL and were OBDI
95's used the OBDII ALDL but were still OBDI
96-97's used the OBDII ALDL and were OBDII

Confusing, I know

Luckily, the OBDI's were simple to install using your stock ALDL. Wht/blk to C207 E. Tan to C207 H

 

So, those 2 wires are the ONLY ones that connecto to it?
Thanks

 

Yup, the rest are already in place, those are the only two PCM contacts

 

I mean *in total* how many go to it? I have to add an ALDL connector to my car.

 

Any info on this?

 

It changes per year, why do you have to add one? Your old engine was OBDI which is the same as what you're putting in there

http://shbox.com/1/DLC_wiring.jpg

 

Because now I am not so sure about the year. I bought it thinking it was a 94 setup, but now I feel that it might be a 95 setup.. You posted that the 94 used an OBDI port, and the 95 used an OBDII port, but was considered OBDI, would this change anything?

 

Id use the OBDI port for all OBDI swaps, less confusion in the end

 

Okay. So I just connect the wires where you told me, and Im good to go?