I am currently doing a 1uzfe swap into my 91 Toyota rv. I am now coming to the part that will be the most difficult for me, the wiring.˟˟I have been reading here and there about the subject and something has been confusing me. Little embarrassed to ask but here we go.

I bought a whole 95 Lexus ls400. Drove it for a while to be sure there were no issues.˟˟My plan was, and is to swap everything over, motor, trans, seats, gauge cluster, cpu, and all the wiring I can use. That said, I keep reading post about people labeling every wire, disassembling the loom and taking out wires and all sorts of stuff. My thought is, other than the trac-control, everything on the motor is going to get used. Everything is IN the loom and plugs into the CPU. WTF am I missing here?

I will be making a small harness that connects a few things to the gauge cluster,˟˟and one plug I think that goes in the ECU.˟˟There are a few things like splicing into the fuel pump ect, but I do not see any reason to pull the harness off the engine and take out wires. What wires? Why?

I am convinced I am missing something so I will humble myself and ask.

 

To redo the wiring is to "clean it up". All you really need is 12V, ground, and signal wires to run and operate.

 

I think a lot of people remove things like the EGR, swap to manual trans, remove traction control, etc. So when figuring out how to patch the LS/SC engine harness to the truck harness it may be less confusing and look cleaner if all the now unused wires and plugs are gone. It's certainly not something you have to do- especially if you are running as much of the LS components as you are.

 

ok, well the loom im talking about is JUST the engine loom. EGR and traction control, how many wires are we talking there? just a few right? and what is the harm in just taking the loom plugs and plugging them in to the CPU?

Now were i see things getting a bit harry is if you were going to use the harnesses from INSIDE the car. there is tons of stuff im not going to use, so I am going to make my own, it would not make sense to try to save that loom.

I have not looked into it yet, but im guessing the epu has some out going wires, things that are relayed from the engine to the cluster, h20 temp, wire from the igniters for the tach, alternator, oil lever/pressure ect.

I guess im just confused because I have not seen a build post where someone is planning on doing what i am thinking....usually that means im missing something! heck I hope not.

 

I can't speak for the LS harness, but just glancing at my SC harness there are at least 40 wires from the 'engine harness' that do not go to the ecu. I'm at your stage and just about to start the wiring though, so I don't know yet what each is for. I'm keeping the EGR but don't have any auto trans sensors to worry about and will be removing most likely 1/2 of those extra wires for my application. I could just leave them hanging, but I want this as clean as possible.

 

so I just went out and took a real look at the connectors. there are 6 from the loom, and 4 on the ecu. so i guess there are some wires, what they do i have no idea! guess ill start there.

So as i said the only thing i will not be using is the trac control. so would i be safe to say i WILL be using most the wires?

I can understand that if someone was not going to use the auto trany they would want to take those wires out. for me, I would think about just warping them up some how. I am not too concerned with with extra wires as long as they are neat.

 

I thought this would get a lot more replies. I guess its good no one is flaming me yet. lol

 

On my 3.4 swap I used almost all of the wires on the engine harness, as they all went to 12V, ground, or signal wires. My auto trans wires I just cut and wrapped inside the wire loom.

 

Great, thanks. Nice to know I'm not totally nuts. I will try to make a good post on exactly what I do.

 

https://www.yotatech.com/attachments...psxdaeyu0t.jpg

Those 2 connectors are the problem. They join wiring harness. I can not find any info on these connectors. I fear that they will have to be traced, and That is was i was missing i think. joy!

 

Some of the Tranny wires come thru the engine harness. So if your running manual then you can remove those, egr, trac control, those each run multiple wires. You can actually loose quite a few wires out of the harness and make it much easier to work with when routing into the cab. Funny how the sub 02's are part of the body harness though... Anyway awesome to see you working on a motor home.