Wiring lt1 questions

[nazar]

Hey guys

 

I have a 94 lt1, ecu and 4l60e tranny

 

I will most likely be converting to a t56 and selling the auto tranny.

 

I bought the engine, tranny, ecu complete with harness out of a burned car and all the wiring going into the cab was burned. Meaning I wont get the obd1 port and wiring.

 

How do i go about fixing this? I will run lt1 edit and i want to tune my car but without an obd1 port i cant. Also i need to reprogram the ecu to bypass the auto tranny, as well as other emission related stuff.

 

Is there a dedicated wiring harness that goes to the auto tranny from the ecu? Do i just cut this out completely since i will be using a t56????

 

I really dont want to get a whole new wiring harness as they are $500 or so from painless.

 

 

THe harness that goes into the engine is all good and intact and the guy supplied the lt1 fuse box as well, but any wiring that goes back behind hte firewall are totally burned up. What are my options?

 

 

I also want to have some sort of check engine light somewhere so that i can know if there are any codes being thrown....

[80LS1T]

You can edit the harness so that it will support a T56 rather than the 4L60e. You just have to take out some of the wires on the harness.

 

You can get an OBD1 connector from any OBD1 car and just wire it up to the PCM where it needs to be wired.

 

I would not pay $500 for a harness after seeing how easy it was to edit the harness. You just have to a have a decent understanding of electrical. You dont have to be a wiring genius but you still have to know to read a wiring diagram. Editing the harness does take some time though...

 

Wiring in a check engine light is very easy with a wiring diagram. Just wire it up the same way the factory did it.

 

Guy

[Z-8]

I'm in the same boat you are man. I've got a '95 lt1 from a cop car, and I'm going to go the way of the t-56. I was never on fire though. Unfortunatly, it's going into a '79 280zx. It's just a little more work.

[Danno74Z]

Nazar,

 

Go to this thread to get started: http://forums.hybridz.org/showthread.php?t=105112&highlight=lt1

 

73LT1Z has authored a fine document on wiring up an LT1 engine in the Z.

 

I too don't have the LT1 ODB1 port but once you have the diagram in front of you and study it for a few minutes you will see only three wires are needed to go to the ALDL connector/port inside the car. There were two styles of ALDL connectors a 12-pin style (94 and older) and 16-pin D shaped (95 and newer) I believe this style is also used on ODB2 systems. In a nutshell you have a ground, mode select, and serial data line that you need to connect to this connector. AKM electronics has a good writeup on this and can provide cables to edit the PCM. I plan on going to a salvage yard and just get a newer GM ALDL connector (leave long leads on wires) and tap into the appropriate plug from the engine harness.

 

Danno74z

[jbc3]

check out http://www.lt1350.com Call and talk to Dana. If you send him the engine harness, he'll do the rest fo you... and he is very reasonable. He did mine, and I got a bunch of extras and it was 275.00 I think.

 

Jody

[mark]

OBD1 connector form your local chevy dealer will be less than 20 bucks. I did my lt-1 harness. I'm an electrical idiot. If I can do it, anyone can. Get a copy of the factory wiring diagram or use the linked hybrid Z thread. Put it on a kitchen table, remove all the loom, remove the wires you don't need and you will be amazed at how simple it is to get that motor to run in another car. Good luck.

[nazar]

so what exactly are you guys sending the stock harnesses out for and paying for? FOr someone to cut off some wires you wont use??? I dont understand what you guys mean by editing the harness, if you mean cutting off plugs and wires you dont need to use, am i just reading too much into this, is it easier then some people make it out to be

 

Here is how i see it, the engine is gonna come with the ecu and most of the wiring harness still plugged into the engine

 

Each plug only goes into a certain connector, most manufacturers do this. So just run the wires from the ecu to whatever places they belong, cut off the ones you wont use(emissions stuff) program that stuff out of the ecu so it doesnt go crazy at those wires not being there, tuck it all away and be done. Send power to the ecu and ground appropriately and youre done right??? As far as gauges, im using all autometer stuff so it will be wired independently... The tranny will be a manual so no need to wire tranny either...

 

How hard does it get? Correct me if im wrong...

[wheelman]

You're pretty much right, it's not that hard it just takes time and a decent understanding of which wire connects to what pin on the PCM plugs.

You can get away without wiring the tranny to the PCM but it works better if you at least give the PCM a VSS feed so it knows when the car is moving or not, the aftermarket speedo will use the same wires so you'll need to connect it to the tranny at a minimum.

 

Get an OBDI connector from a junk yard. Pretty much any GM car with OBDI will work and if you aren't going to be taking it to a shop you only need to connect 2 of the 3 wires (ground and data) the mode line can be left disconnected. If you are planning on a shop working on your car then connect all 3.

 

As for sending the stock harness to someone, thats a personal choice, some people are very intimidated by the shear number of wires in the harness and don't want to mess with it so they send it out to have the circuits that aren't needed removed and the rest rebuilt to place the PCM in the desired location relative to the engine.

 

When you say the gauges will be wired independantly do you mean that separate connections will be made to existing sensors (water temp, oil pressure, tach, speedo, volt, etc...) or will you use different sensors for the gauges from those used by the PCM? If you plan on using separate sensors then where they are placed gets complicated, if you are using the existing sensors with new gauges then new circuits must be run to feed them. This is why it really pays to understand the wiring harness before removing things that at first glance you think you won't need.

 

My suggestion is before you decide what you are going to remove sit down with the harness and complete wiring diagrams for both the donor car and the Z and figure out what everything is, where it connects in the donor and in the Z and label it all, then remove the circuits you won't need. Be sure to understand how the aftermarket tach and speedo connect either to the PCM or the engine/tranny and run those circuits accordingly. One thing to keep in mind is that you will most likely be cutting those connectors off to either shorten or lengthen just about every wire in the harness so don't rely on them to identify the circuits.

 

Again, this isn't a hard thing to do but it takes time and can be confusing due to the shear number of circuits you're dealing with.

Good luck and don't hesitate to ask questions if you get stuck, be sure to search first though as this has been done and documented a couple times on here already.

 

Wheelman

[nazar]

if the ecu in a camaro sits inside the engine bay and so will mine and im using hte same engine, shouldnt all the wire lengths already be ok? Why would they need to be extended?

 

Also...its going into a 71z which was carbed so there really arent any ecu or engine wires that are in the car, plus I bought the car with a 327 sbc in it already so some things are already wired up(the stock tach and speedo were even done correctly)

 

I will try to keep it as basic as I can. I wont use ANY emission equipment to clean up as much wire as I can.

 

I know the donor car cought fire inside and only the interior wiring was burned up and I think the map sensor is the only piece that burned up according to the seller...everything else is intact.

 

We'll see, the engine assembly should be here friday. Im excited because from the pictures looks like the lt1 is already heavily modified, could even be a stroker...its got some sort of domed pistons, rocker arms, new valve springs(i assume its got a cam then) intake, long tube headers, etc...may have scored on this buy

 

The rear end on the donor car was broken, so i assume the car was drag raced, and might have the stock 4l60e tranny modified as well...which i will most likely sell and do a t56(i know just keeping hte auto would make things much easier and cheaper, but im a hardass and I just dont see the car being an automatic)

[jbc3]

I suppose that you are right in the fact that someone else is cutting off wires and connectors, but there is alot more.... No headaches and no problems.

Why did I have someone else do the harness conversion, it was just plain EASIER. It would have taken me many hours to do what he did and it was a couple of hundred dollars well spent, IMO. I had him give me leads for the start and power circuit, tach, speedometer, temp, oil pressure, reverse lights. SES light, fuel pump, AC request, low and high speed fans. Everything was well marked and all of the circuits that I did not use/want were bypassed in a way that would prevent the SES light. You can't just hack the circuits that you don't want if you want to use the LT1 PCM. I like having the PCM fully functional and I can monitor the engine with Datamaster and edit at will with LT1-edit.

 

Good luck and do as you wish,

 

 

Jody

[nazar]

I suppose that you are right in the fact that someone else is cutting off wires and connectors' date=' but there is alot more.... No headaches and no problems.

Why did I have someone else do the harness conversion, it was just plain EASIER. It would have taken me many hours to do what he did and it was a couple of hundred dollars well spent, IMO. I had him give me leads for the start and power circuit, tach, speedometer, temp, oil pressure, reverse lights. SES light, fuel pump, AC request, low and high speed fans. Everything was well marked and all of the circuits that I did not use/want were bypassed in a way that would prevent the SES light. You can't just hack the circuits that you don't want if you want to use the LT1 PCM. I like having the PCM fully functional and I can monitor the engine with Datamaster and edit at will with LT1-edit.

 

Good luck and do as you wish,

 

 

Jody[/quote']

 

 

the circuits you did not use you said were bypassed, how? And if you have lt1 edit, cant you bypass those yourself? If i cut the wires i dont need out, cant i just turn those circuits off with lt1 edit? I am not questioning you, just brainstorming to see how i will go about it.

 

If i can cut off the wires i dont need and edit them out with lt1 edit, then its all good. If you cut wires you dont use, does that make the ecu go crazy? I understand things like egr and all, but what do people do about gauge cluster harness?

 

-----------The wires that go from the computer to the stock dash gauges in a camaro for example, we dont use that at all do we? And if you just unplug it, does the ecu go to limp mode and throw a CEL ???

[80LS1T]

When I swapped my 93LT1 harness out for the 95 harness I went through each connector on the PCM and actually removed the pin right from the connector for the stuff that I didnt need. So I dont have a bunch on wire ends just hanging there. You will need power and ground to the PCM plus a few other fused power wires going to the harness. Not a big deal with a good wiring diagram.

 

The Gauges are wired sperate from the engine harness and PCM. You would have a few wires going to the cluster from the PCM but thats it. If you go with aftermarket gauges all you will really need is the VSS wires.

 

As far as the check engine light, you will have to edit the PCM to turn off codes that wont apply to your engine. Things like the VATS, EGR, auto tranny codes, and other emissions stuff can be turned off with just a click on Tunercat.

 

I wouldnt have paid $275 for someone to do what I did to the harness in a few hours of my time but I like doing everything myself, plus I saved a few bucks!

 

 

Guy

[jbc3]

VATS,EVAP,Canister purge are some for example.

 

LT1-edit has a switch for VATS, but it doesn't work (at least the version I have it does not 1.9), so you need to bypass it or use Tunercat. LT1350.com put something in the harness to generate the signal the PCM looks for. Things like the canister purge, evap and CAGS the computer looks for a load to make sure the devices are present, so he puts resistors in the harness and wires them to simulate the devices. CAGS is easily edited by setting the tiggering load/speed to something out of any normal driving situation (150 mph at 10% TPS). Just cut the wires and you will have the SES light lit (if you use it) and codes always present. Neither is a disaster, but I wanted to have a working SES light and not have to deal with the annoying codes. Also... if you use the PCM to control your fans (good idea IMO, since you can edit the temps to control the fans) and you have codes, it turns on the fans full all the time.

 

As far as the gauge cluster you don't use it, the engine wiring harness is just the PCM harness and the wiring harness from the 2 weatherpack connectors on the passenger side fender forward. The wires for the gauges then come from the PCM . The computer simply passes on the signals to the gauges, it doesn't monitor their output... so no codes. It does monitor the SES light though.... so unless you put a resistor in line to simulate the bulb or put in a bulb, the fans go on and stay on and you have a code.

 

Have you used LT1-edit yet? If not, find someone near you and look at the actual features. Some things can be edited out by adjusting the settings, but some of the basic "checking features" of the sensors can not. I have been using it since the beginning and was a Beta tester for several of the versions.

 

Jody

[wheelman]

I totally removed all the circuits that weren't used (removed the pins from the PCM plugs like 80LT1 did) and have no problems with codes. The circuits removed include evap purge, all tranny inputs/controls, EGR, AIR PUMP, PS, VATS and AC. I did have to put a resistor in line to simulate the SES light but no others were required. jbc3 is correct about the SES light and what the PCM does with the fan(s) when a code is generated. The PCM will want a VSS so it can control the IAC during coast down, if you don't have one and you use the tranny to slow down while stopping the engine will have a tendancy to die.

I use Tunercat and it's possible to disable and/or adjust the settings so that the removed circuits have no affect on the operation of the PCM. If you decide to go with a T5 let me know and I'll give you a calibration file from a 94 Camaro with a manual tranny as a starting point. You'll still need to edit it but the auto-tranny settings will already be set to default factory settings used in a manual tranny car.

 

Wheelman

[Danno74Z]

jbc,

 

Can you email me as I am having problems emailing you through HybridZ.

Danno@v8z-car.com

Thanks

[nazar]

how did you guys deal with the fuses and relays? my engine came with the whole harness plus the rest of the cars harness and fuse box, but 1/2 the **** in there i wont use, like lights, headlights, turnsignals, ac, power steering, etc....

 

 

And how does that fuse box wire into the engine harness? Looks like 2 different harnesses to me? THe one coming out of the ecu looks simple as it all plugs into the engine at their specific spots...but the rest im lost on...fuse box, relays, etc...i dont even know how the fuse box hoooks up to the ecu

[nazar]

might be a simple question...

 

How does the ecu harness get power???? There is nothing in the harness that goes to the battery?

 

ALong with my engine i recieved the camaro huge fuse box along with a wiring harness that is even larger then the engine harness...wtf am i to do with that???

 

Im totally lost. I understand the wiring harness that plugs into the ecu and all the appropriate plugs on the engine, but what from there?? How does it all get power?? What is to be fused?

 

Do i really have to use that second harness someway? Its got all the rest of the wires for lights, switches, interior ****, etc...and that ugly fuse box

 

Is there an easier way>??>

[80LS1T]

If you buy a factory service manual or do what I did and get a subscription to ALLDATA ONLINE, you will be able to figure out what you need and dont need. There are a few power and ground that come right out of the PCM. Some power wires will need to be wired to fused +12V battery feed and some will need to be wired to fused +12V ignition feed. Its really quite simple once you get a wiring diagram infront of you just as long as you can read a wiring diagram.

 

Here are the wiring diagrams that I used...1995 LT1 Wiring. If you can understand those you will be able to figure it out just fine.

 

You dont need the big fuse box but you could use it if you wanted to.

 

 

Guy

[Danno74Z]

From my understanding you don't have to use any of the Camaro's interior harness unless you really want to try and modernize your existing Z but I would hold off on that for now. You have to remember that between your Z and the Camaro spans 20 years and auto electronics exploded in that time span. My suggestion is to just put away the Camaro harness for a little while and just concentrate on you Z small fuse panel/box and the old wiring. Keep it simple for now. Don't worry about anything except the ignition to the fuse panel; fuse panel to starter and the battery hookup. When you look at a schematic even a simple one it can be daunting. Block all the rest of the BS out and go from this point to that point through either a relay if your carrying a lot of current or a switch. EVERYTHING first goes through the fuse panel (or should). Do one circuit at a time.

 

Danno74Z

[nazar]

If you buy a factory service manual or do what I did and get a subscription to ALLDATA ONLINE' date=' you will be able to figure out what you need and dont need. There are a few power and ground that come right out of the PCM. Some power wires will need to be wired to fused +12V battery feed and some will need to be wired to fused +12V ignition feed. Its really quite simple once you get a wiring diagram infront of you just as long as you can read a wiring diagram.

 

Here are the wiring diagrams that I used...1995 LT1 Wiring. If you can understand those you will be able to figure it out just fine.

 

You dont need the big fuse box but you could use it if you wanted to.

 

 

Guy

 

as far as out of the ecu, the whole harness seems to have a purpose and a connector at the end, i dont see any open ended wires that hook up to anyhting like power or ground or anything....there are 4 plugs that come out of the ecu and go all over, all end in a connector that has only 1 specific place it will plug into..am i missing something?

 

http://shbox.com/1/harness.htm

 

that is what i am looking at. Where does it go to the battery and ground? And where do i tap in the ignition wires? I will be running all autometer gauges to make things easier. I rather not use the ugly camaro fuse box...its mind boggling.