OBS chevy LSx wiring

How are you guys running the two harnesses? What about ECS controls in the cab? A/C, tach, all the gauges, etc. Is everybody keeping the old computer hooked up and running the 0411 seperate? I'm primarily concerned with the speedo and tach.
I guess I just don't get how the two harnesses work together. I'm on a Macintosh right now, so sorry if the text is messed up...
Thanks.

Can I just remove the old harness entirely? But then what about the tach/speedo...ughhhh

current setup is GMPP350HO, TBI (90 lb inj's), AFPR, all the good stuff. DIY tuning

so guys are running two isolated harnesses, huh? One for the powertrain, then one for the chassis?

I bring up A/C because of the computer (7747).
I'm aware of standalone engine harnesses and that's great...but what about retaining my 1991 gauges and controls?
I hate macintosh computers

the only real thing I think I need to know from the LS1 computer is check engine, tach, speed
A/C switch too.

There's no need to run both harnesses that I can see. Your gauges are pretty much standalone, so you'll keep what's needed out of the c100 connector on the firewall and remove what you don't need. you can tie the C100 wires into the new harness for temp sensor, tach, oil pressure, tach, A/C etc. are you going to have a custom harness built or use the new one?

I'll probably use the one from the donor truck. A tad on the pricey side for a new one!! lol

So that big azz clump of wires on the passenger side firewall is the main harness, huh? And that's what I'll be splicing into, obviously. Cool.
So the computer (TBI) runs through there, also? In addition to the cluster? Yah, I think they all go through there. I'm all ears, man. Thanks for the reply.

I know I sound like an idiot, but I've never messed with the harness. I've ran a few wires and pinned the computer for e-fans, a wideband and a MAT sensor, but I drilled through the firewall for that.

You're doing good, no question is a dumb question. You should have heard me when I got started. LOL Some of the wires go through the C1oo and others go through the passenger side under the plastic cover. Just to be familair with everything trace the wires back from the engine, injectors, etc... back to the firewall and it will give you a sense of comfort. Greg RedHeartBeat) has done a pre 96 swap and can probably answer more of your questions. I've been messing more with with 96-2000 vortec swaps but they are pretty much basically the same except for the wiring.

i am putting the final toutches on my obs to lsx swap (98) i am only running one pcm the 0411. all of my guages work tach, spedo etc as well as all of the abs and 4x4 stuff.

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Originally Posted by 98 4X4 burban

i am putting the final toutches on my obs to lsx swap (98) i am only running one pcm the 0411. all of my guages work tach, spedo etc as well as all of the abs and 4x4 stuff.

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nice job, man. yah, I figure the OBD1 stuff should probably mostly removed...wish I had a 96-up lol

The 0411 pcm is great compared to the older black ones.

the 0411 is the newer vortec pcms correct?

Yes, you're correct.

wow...I am totally lost. I wish one of you would come to my shop and just magically make this thing work....I hate wiring.

Josh

If you have pinouts for both engines it's not very hard just takes some patience.

glad to hear that lance im sure ill be calling you hahaha with many questions so prepare yourself :LOL:

Feel free, you got my number now.

Lance helped me when I had questions too. He understands this ****!? lol:) No...seriously, what I did, was get the GM Service Manuals(theres two) from E-bay. It has everything you need to know regarding the wiring(and everything else) on your year truck. They come in VERY handy with anything you work on.

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Originally Posted by LS1GMCTruck

Lance helped me when I had questions too. He understands this ****!? lol:) No...seriously, what I did, was get the GM Service Manuals(theres two) from E-bay. It has everything you need to know regarding the wiring(and everything else) on your year truck. They come in VERY handy with anything you work on.

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are you talking the HAYNES manuals or w/e

I am about to put a 5.3 out of an 03 in a 98 that had a 4.3, can I run the truck totally off the new ecu and just re pin certain things? This is hellfires truck also.....

Yep, run it completely off the newer PCM.

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Originally Posted by Wtfan18

are you talking the HAYNES manuals or w/e

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You want the Factory GM Service Manuals, that the local Chevy/GMC dealers used. Not the aftermarket haynes manuals. They seem expensive, until you have them and see how useful they are, on everything you go to do, on your truck. Only way to fly.:)

www.Helminc.com is where I always bought mine.

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Originally Posted by RedHeartbeat

Yep, run it completely off the newer PCM.

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neone have any pics of where they mounted their pmc etc?

I extended my wires and put the pcm on the passenger side and put my relays and fuses on the drivers side. Pretty much all plug and play.
http://i33.photobucket.com/albums/d7...g?t=1208893084

http://i33.photobucket.com/albums/d7...g?t=1208893207

what is the relay/fuse block item on your pass side fender nitrous?

nitrous what did u do for the gas gauge did use the stock pcm ?

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what is the relay/fuse block item on your pass side fender nitrous?

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The small cover on the right houses both LS1 fan relays and the cover on the right houses an extra fuel pump relay, extra A/C relay, fan 1 and fan 2 30 amp fuses, an extra 10 amp fan fuse, an extra 20 amp fuel pump fuse, a 10 amp PCM battery fuse, a 15 amp A/C fuse, an extra 15 amp pcm ignition fuse, and 3 extra fuses for fuel injection if needed. I made the small plug and play harness with exra features to use in other vehicles.

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nitrous what did u do for the gas gauge did use the stock pcm ?

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The gas gauge is standalone from the PCM so the sender is hooked up just like factory.

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Originally Posted by NITROUS

The small cover on the right houses both LS1 fan relays and the cover on the right houses an extra fuel pump relay, extra A/C relay, fan 1 and fan 2 30 amp fuses, an extra 10 amp fan fuse, an extra 20 amp fuel pump fuse, a 10 amp PCM battery fuse, a 15 amp A/C fuse, an extra 15 amp pcm ignition fuse, and 3 extra fuses for fuel injection if needed. I made the small plug and play harness with exra features to use in other vehicles.


The gas gauge is standalone from the PCM so the sender is hooked up just like factory.

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Nice relay/fuse centers. And where did we source these from?

Very nice, can't wait to get mine started.

on the 98 it uses the pcm for the gasgauge

beater6.0, your talking about the purple wire pin 9 on the blue connector right? I don't know why it's needed to be honest unless the sending unit has changed in 98. It's not used on 96-97 and I have a set of 98 and 2000 tahoe gauges that both work in my truck without that wire. Let me browse through the factory manual and see why you would need it.

What I see is that the purple wire goes from the VCM (Fuel gauge level) through the C100 to the cluster (fuel gauge). I'm not sure why you would need this because the diagram shows the purple wire to go to an external fuel gauge and from there to the cluster. I really don't think you need this wire from the looks of the schematic but I could be wrong.

its been awhile but itried bypassing the pcm but noting happened but at the same time sendingunit went out so going to worry about another day

if you guys had to guess how many hours do you think it will take to get my nelson harness all wired in?

shouldn't take to long just lay it out and seperate it then set it on top of the motor and start plugging away. just make sure u dont let let it touch moving or hot parts, id say hour

yea my gas gauge is controlled by the pcm.

the 98 pcm ?

The only reason I can find to use the ppl wire is for the idiot light in the cluster. If anyone can find something different let me know. I wouldn't use the 98 PCM just for this when you can probably use pin 54 on the LSX PCM C2 connector (fuel level sensor). If you like 2 computers use it, I'm not trying to tell anyone not to.

thats how my truck is set up right know and soon as i get un lazy im going to do somthing about it

well all i can say is i hope my stupid A** can figure it out without messing stuff up lol if i can do that ill be extremely happy. cuz i know nothing about all these pins etc..

My original purple wire, for the fuel level gauge, coming from the tank sender, is still hooked up as it came from the factory. The fuel level gauge stopped working though. Any ideas? (I did just have to replace the fuel pump, cause I think I burned it out by leaving the key on for a couple days. But the sender & the fuel pump are wired separately, so one should not effect the other.)Do fuel senders go bad? I'm scratching my head on this one.:duh:

Yes, they are very sensitive to any type rough movement. Check out this link, it's pretty cool. If the wiper is damaged or pulled away or worn from making contact the sender will quit working. Here's a pretty cool link that shows how a sender works. Just click on the play button.

Howstuffworks "How Fuel Gauges Work"

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Originally Posted by NITROUS

Yes, they are very sensitive to any type rough movement. Check out this link, it's pretty cool. If the wiper is damaged or pulled away or worn from making contact the sender will quit working. Here's a pretty cool link that shows how a sender works. Just click on the play button.

Howstuffworks "How Fuel Gauges Work"

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Thanks again buddy.