98 5.7 vortec swap to LM7 5.3l need wiring help

I'm having trouble finding exactly what wiring is required for the modified LM7 harness to swap into a 98 sierra with a 5.7 vortec.
I have followed lt1 swap's guide and removed all the emmisions etc. I'm keeping the 98's 4l60e so those wires are staying.

-will I have to make up an obdII connection for the LM7 ecu?
-what other modifications will i have to make to the LM7's wiring harness?
-what can i remove from the 98 vortec wiring harness?
-is there anyway to use the LM7 a/c compressor?

I also need some help with deciding on which water-meth injection to get. It's going to be a turbo-ed engine and it should make about 650hp. I'm not sure how many cc's I should be looking for in a kit. I'm not looking at spending alot on the kit either.



Any help would be greatly appreciated. Thanks

LT1swap.com Plenty of wiring info. Or you can do what I am planning on doing which is using my stock harness to run my LQ4.

im new to wiring engines, and i do agree its a great site, but i would like some specifics. Im just trying to avoid messing up the wiring harness, and i want to keep things as simple as possible without soldering all new connections etc.

There are a lot of videos on youtube about de-pinning the main plugs for the PCM which will make it a whole lot easier to do the harness swap. Follow the diagrams carefully on LT1swap.com and you cant go wrong.

I have already de-pinned the harness(as per lt1swap.com), im just wondering if ill need to make up an obdii connection etc, specifically for this swap. It seems that the site is more so geared towards installing the engine in a vehicle that isnt already equipped with a computer etc. An example would be which computer should i have running the fuel pump?(Does it matter?) which should have the Alternator connection?

I am certainly no expert on this, but will the 98 fuel pump handle the required pressure of the later engine? You may have to run the later pump, which would mean running that off the later computer. I think you will need the obd11 wired to suit the newer engine also, as you will be reading codes from the new engine.

The '98 fuel pump is more than up to the task for a stock engine. The fuel pump relay can also be used but must get it's actuating power from the new PCM. I found this out by mistake. I used my existing relay/computer and when I started the engine, it died in about 10 seconds. Turns out, the old PCM would power the relay and the system would prime for start. After it started, the old computer powering the relay didn't "see" any information coming from the engine(crank signal, rpm, etc), so it would de-engergize the relay. I simply used the fuel pump relay wire from the new PCM to energize the existing relay. It worked like a charm.

Your new PCM should power the alternator, but I would retain the existing battery idiot light wire(if equipped).

As for keeping things simple as possible, you need to power the new PCM. You will also need to get it flashed to remove the VATS(Vehicle Anti Theft System).
You need to retain all your wires for the instruments(oil pressure, voltage, rpm, water temp,).

As for soldering connections, there will be some of that required. I don't rely on crimped and taped connections on something that I will be driving. Nothing is worse that being stranded somewhere due to a loose connection. Solder them and shrink wrap them.

Not sure if you can use the LS type compressor in these trucks. I read something about it and it requires frame notching.

Since you already have an OBDII system, only one wire is required to run to the new PCM. This way you can read any codes that may pop up.

Right on man, thanks alot. I will be using an aftermarket fuel pump, not quite a stock engine haha. I will solder i just didnt want to redo all the connections thats why im using both ecus.
-Would that single wire for the obdII allow for reflshing of the Ecu? Happen to know which wire?
-will i need to get the old ecu flashed at all? or am i good to just rip the unused wires out of the old harness?

By using the original fuel pump relay, alot of your wiring is already in place. Simply remove the actuating wire coming from the old PCM(ECU), and attach the fuel pump relay wire from the new PCM in it's place.

Reflashing of the computer requires special software. Not sure what's involved, but I sent mine to Brendan Patton on LT1swap.com. Turnaround time was about 1-1/2 weeks. He'll need to know everything about your truck, from tire size to transmission used to gear ratio. He can also program to actuate electric fans if the original donor vehicle did not have them. Cost was $75 and shipping to him. His shipping is included with the cost.

http://lt1swap.com/programming.htm

Nelson also provides these services and can also modify the programming for engine modifications. Since my engine is stock, I did not need any additional programming.

The single wire for the OBDII is only to read codes that may come up.
Reflashing of the old PCM is not required. I don't think the the old PCM is required at all. I still have mine but it is not used for any of the functions of vehicle running or driving.

The PCM wire for OBDII may depend on what year harness/engine you're using.
http://lt1swap.com/wiringharness.htm

Thanks again man, you just saved me a bunch of time.

Make your truck simple,get rid of the old black box,the 411 PCM will run everything in your 98 with the correct re -pin and reflash.

Search for a member on here by the name of Lextech. He sells a kit to retain the vortec AC. It requires moving the alternator to the passenger side and the vortec AC goes in place of the alternator location. Also look in my sig. there is a link I labeled Not ALLDATA. The username and password are there as well. There you can search your truck and the vehicle the motor came out of for wiring schematics. Its helped me since I lost my copy of alldata I had stored on my computer.


Here are the pics of the kit lextech sells. Its runs around $250.

Attachment 8187Attachment 8188Attachment 8189Attachment 8190

Quote:

---

Originally Posted by tfi racing

Make your truck simple,get rid of the old black box,the 411 PCM will run everything in your 98 with the correct re -pin and reflash.

---

Agreed. Good thing my donor vehicle came with the 411 PCM. No searching to find one.

Quote:

---

Originally Posted by capricefrk013

Here are the pics of the kit lextech sells. Its runs around $250.

Attachment 8187Attachment 8188Attachment 8189Attachment 8190

---

That's a nice setup. I was wondering how guys with vortec injected 5.0/5.7 were getting their A/C setups working on the LS engines.

Thanks alot guys. I've decided no a/c, removing the condensor will give me room for the intercooler. Although that is a pretty slick relocation kit. Will all the gauges work if I get rid of the old computer? Ive read that their is issues with the tach and speed signals?

Just a couple pics I took about a week ago. I have tests this week so my progress will slow. I have the turbo, bov, wastegate, injector adapters, fuel pump on order. I also picked up an upgraded 4l60e with shift kit, billet servo, upgraded plates and a few more goodies, and i got a custom 3400rpm stall tourque converter. I will prolly make a post when everything is done just to give an idea of what the whole process was like.

Sorry they are turned. Uploaded on my phone

All your guages will work. I would keep the original oil pressure guage wire and temperature wire along with their respective sending units. The tach and speedo will be run by the new PCM. It will have wires for those guages.

So you're suggesting running both computers right?
Or do you mean use the original coolant temp and oil pressure sensors and repin them into the new pcm?

Quote:

---

Originally Posted by shmiet

So you're suggesting running both computers right?
Or do you mean use the original coolant temp and oil pressure sensors and repin them into the new pcm?

---

No get rid of the black box.Use the OBS oil and water senders ,they will connect to the 98 truck wires.The 411 PCM has no need for oil pressure input,before the engine goes in re-tap the passenger side head for the old water sender,the driver's side water sender is needed for the 411 PCM.

Oh right on. Thanks man. Do i just repin the tss, brake, speedo, tach, check engine, and fuel pump then to the new pcm? Is it possible to make a lm7 pcm to work like this or does it have to be the 411?

For your temperature sender, here's some info that I would have used if I had it:

http://www.impalassforum.com/vBullet....php?p=2667060

This was passed along from another member and I'm just doing the same.

I'm not sure if the new PCM will operate your temp and oil pressure guages. The only way to tell is by the use of a wiring diagrams for your new engine/harness and your existing truck wiring diagram.

In the new PCMs, all the sensor wires are fed into it and the PCM then sends a signal to the logic board in the instrument panel. The logic board deciphers the signals and makes the guages work accordingly. If your existing instrument panel works the same, then maybe the logic in your instrument panel can decipher the signals coming from the new PCM.

Does the wiring for the temp and oil pressure go to the gauges or?. That link still work? says page not found.

Do the Chevs use a BCM(body control module)? I know my swap is different, but I needed to use the BCM out of my wreck to power up the dash guages. Some worked, but not all until I had hooked up the BCM. And that included the diag reader plug.

They do have a BCM; however, I haven't read about anybody having issues with that, when doing this swap. It seems to be an issue with the gauges not being able to communicate with the ls pcm gauge signals. I think i need to splice into the tach and speedo wires. Im not sure how the oil pressure signal wires up- from what a post in this thread says, i can connect directly to the sensor, as the pcm doesn't require the signal. And coolant temp will require a obs coolant sensor and a ls coolant sensor, one for the new pcu and one for the gauge. And i can use the 896 pcm and remove the "black box" and use the black boxes- brake, fuel pump, and check engine light

Can someone please confirm this? I really appreciate everyones help. I apologize that some of this may be trival for you

i have a stand alone harness & it has a wire for speedo & a wire for tach. speedo works but my tach is off. i need to put a resistor inline. oil pressure is just ran off the sensor straight to my gauge. i'm using the LS sensor with a single wire plug i bought off ebay. for coolant you can run the factory LS sensor on the driver side that will go to the ECU & a separate sensor on the passenger side to run to your gauge. you will have to buy an adapter for this, or you can buy a 3 pin coolant sensor with a mini harness off ebay. it's one sensor that runs to the ECU & has a separate wire for a gauge. that's what i have in my truck & will be running the swap on my IS300 swap. you can look through my build thread & see the parts i used, should be linked in my signature.

Sweet build man. Freaking clean. So did you get rid of the black box or did you run them together?

thanks man. i'm only running the LS ECU. i don't have ABS or Neutral safety switch & without the NSS my gear indicator lights don't work & reverse lights don't work. i'll figure that out eventually.

Thanks for all the good info. I noticed that you were looking at the weather sea,l with all the wires going through it. DId you have to remove any of the wires from that? I have got around to ripping the harness out yet. And did you swap the brake, check engine, and fuel pump wires from the old ecu to the new harness? And the 896 pcm will work right?

Try this link for the coolant temp sensor:

http://www.impalassforum.com/vBullet....php?p=2667060

Thanks, im definitely going to do that.

Quote:

---

Originally Posted by shmiet

Thanks for all the good info. I noticed that you were looking at the weather sea,l with all the wires going through it. DId you have to remove any of the wires from that? I have got around to ripping the harness out yet. And did you swap the brake, check engine, and fuel pump wires from the old ecu to the new harness? And the 896 pcm will work right?

---

i didn't do anything to the brake wires. the new harness from Nelson came with an OBD2 port & light. i just tapped into the factory CEL so i have the one in the gauges & one under the hood. fuel pump just needed 12 volts that comes from the new harness.

i think i removed most of the wires on the passenger side plug. that plug is a little different on the 97/97 then the 96. that's how i realized i had the wrong year harness at first.

Would you say it's easier to use both computers? that way i wont have to mess with the wires going into the cab etc correct?

i don't think so.

I think I'm in way way over my head haha.

i thought the same thing. now i'm doing a swap into an IS300. it's really not that bad.

Some wiring diagrams certainly help in these type of situations. Here's one for your truck:

http://www.ebay.com/itm/1997-Chevrol...bf542e&vxp=mtr

Not sure of the year of the new engine, but I would consider looking into getting one for that year as well to see what the differences are between the 2 vehicles for all the systems you are asking about; i.e. guages etc.

These projects are very daunting initially, but I found if I printed off as much info as I could find, and I was lucky to get a very good CD for the GEN111 vehicles(Aussie versions), that it made the job a lot easier. I did my own wiring mods, and found the wiring diagrams I had made it so much easier.
So, really it means plenty of research, and print as much as possible.
Certainly the 2nd conversion would be so much easier.

Ian, I agree. I modified the stock 6.0 harness with the help of various web sites, Youtube videos, and genuine GM/Chevy service manuals with the wiring diagrams and all other pertinent info needed for such a task. While doing the swap, I swore to myself a few times that I would never do it again. After completing it, and finding out how much it was worth it, I would do it again, although there would be some things I would do differently. Live and Learn!!!

Thanks for the support guys, im gonna keep working at it. Im gonna use both computers just for simplicity, and will probably eliminate the black box when I have a better understanding. From what i can tell i have the ls harness pretty much done. I need to work on the fuse block, setting up the obdII and the electric fan, and ofcourse tearing down the old wiring harness.

Can i use the factory fuseblock for powering the electric fans and powering the harness?

Can i get rid of the white sensor plug on the oil pan? i think its the oil level sensor.

I can't see why you can't use the factory fuse block for the electric fans. The fans have to run on separate relays though. The relays are powered by the PCM which senses engine temp and turns them on when the temp goes up.

You don't need the oil level sensor. I left mine in but took the wire out of the harness.

One of the advantages of buying a whole vehicle to get the bits for a conversion is that you have plenty to choose from. I used the fuse box from my donor car, so things like the fans(from the donor car as well as the radiator), and fuel pump relays were all there with the wiring ready to go. I just basically wired the ignition wiring from the PCM straight to my trucks ignition switch. It wasnt as easy as it sounds, but not that bad.
So, I suppose what I am saying is, get as much gear you can from the engine vehicle.
Just makes it a lot easier in the long run.

And I nearly gave up a few times as well. Just take a break for a while if it gets to you.