cartune777

hey not to beat a dead horse or anything but ive searched numerous forums about this swap and nobody says anything about do it yourself wiring. many people have done it so my questions is this, is there anyone who has a wiring diagram for what wires go where from the 3.4 harness to the truck body harness. any and all wiring tips will help. i know i can buy a a harness from ORS
but that is out of the question.

ps my truck is a 91 the donor motor is a 96

fillsrunner4

I did it and showed it in my build threads
Go to toyota and ask for the schematics. They may or may not give it to you. You also have to get the diagrams for your exact truck and exact motor! try techinfo.toyota.com they sell the shcematics. Wirirng changes a little everyyear so your going to have to get the exacts for your specific build

two plugs for the dash harness and two on the engine harness. these two need to be pinned out together. and the ecu is going to have to get the power to the missing plug your gonna have to get

Turned the two plugs and made it into one
body harness side

engine side

Together

mt_goat

Here's the 3.4 section:
https://www.yotatech.com/forums/f160/

cartune777

wow thanks guys, ill check toyota and keep you posted

RobD

Toyota Techinfo really is your best bet. I can send you the pdf files of the 91 4Runner harness, but I only have 97 Taco wiring for the 3.4.

What you need to do is make a list of all the pins on your body harness and what they do, then find the corresponding function on the 3.4 harness. It's really a matter of cross-referencing them.

Elvota

I have some info on my thread as well.

https://www.yotatech.com/forums/f160...5/index10.html

Post #240 has a break down of what I did... but each application is going to be different.

By the way... I moved this post to the 3.4 section.

cartune777

awesome, ya i would like the pdf on the 91 4 runner, so i pretty much just make a harness from the new 3.4 wiring to plug into the two connectors down by the old ecu?

cartune777

i see im pretty much clogging this part of the forum with questions but thats how i learn so if im annoying any one sorry, maybe someone else has these question and it will be helpful to them in the future. im so close to starting it i think. the only thing im really stumped on is this: which wires of these relays have to be hooked to the ecu and 90 body harness?

this was taken from elvotas thread, i also have a 96 3.4

cartune777

anyone?

RobD

Dude, just off the top of my head, you don't need to do anything with that relay. All you're trying to splice are the two under dash plugs on the passenger side, IH1 and IH2, if memory serves.

I'll have to check my notes when I get home tonight, but I'm pretty sure you leave those ones alone.

Give me about 10 hours and I can tell you for sure.

cartune777

thanks man,my ecu has 4 plugs going into it, 3 from the engine harness and one from the vehicle. then i have the 2 body plugs(Grey and white) that come off the engine harness which are called Ik1 and Ik2 in my diagrams, which i believe are the same as Ih1 and Ih2. if you could help that would be great

RobD

Do you have this computer?



If so, you need to scavange one of the plugs from your 3.0 harness and splice the power wires onto it. On my 97 Taco 3.4, I had to splice E2 to battery +, E4 to W (on wiring diagram), E6 to ACT, and so forth. There were 10 wires that had to be spliced onto that plug (call it plug E).

Man, I'm looking at my notes and stuff that seemed so clear a year ago now seems like Greek. Go through your IK1 and IK2 plugs plus plug E, and cross reference to the functions (or similar functions) on your IH1 and IH2 plugs. For example, the circuit opening relay on the body side of IH1 pin 23 is IK2 pin 5 on the 3.4 engine side of the harness. The stop light switch is IH1 pin 5 on the body harness and pin 20 on plug E.

Clear as mud?

cartune777

thats almost dead on to mine, could you post up your notes? just for reference

cartune777

it would be very helpful

RobD

Scanner no workee.

If we have the same ECUs, the three connectors on the harness plug right in with no modifications. The fourth one, on the far right, is the one you'll have to get power, etc., connected for the computer to run.

Like I said before, map out each pin and its function on the 3.0 body harness and find the corresponding one on the 3.4. There are some pics of the ones guys have done on here. Mine was on Excel, but I got it from someone else. Sorry, I no longer have that file.

I'm not much help tonight. My apologies.

cartune777

its alright, i think i pretty much got the wiring done, the only thing im confused about is the 4wd and starter wires. is the starter wire somewhere on the 3.4 alt harness and where does it need to go?

RobD

I never did sort out the 4wd wires. I pulled all my VSVs for the ADD system and put on manual hubs and permanently hooked a vacuum line on the sleeve for the ADD.

All I remember about the starter wire is that is was the one wire that didn't get spliced. When I tried to start my truck for the first time, I had no cranking. Plenty of fuel pressure, but nothing else. I dug into the manual and found the starter wire (black with a white stripe) unattached to anything. Ran it to the plug on top of the starter. Started first time.

Then the battery wasn't charging. Turned out I used the 3.4 alternator harness, which did nothing. I swapped the 3.4 alternator plug onto my old 3.0 harness and it fixed the charging problem.

screamer76

you can either run that starter wire(b/w) through the firewall with the engine harness and then splice into the sta circuit from the ecu, or you can splice it in to the starter relay(b/w wire), which resides in the fuse box in your engine compartment. that wire is part of the engine harness for the 3.0, and connects to the fuse box with the alternator wires for the 3.4, so it gets lost in between.

rajet

The starter wire on my 98 t100 3.4 5spd harness went to a different series than my 95 4runner auto trans. I left the origional 3.4 starter wire unused next to the battery wire wich i used. I used the 2 3.0 starter wires coming from the trans. and picked up the two spots in the middle of the grey 4.3 plug and pinned them to match the drawings i downloaded from toyota tech info. Things seemed pretty much straitforeward after i cipherd the difference between the two start circuits. If yours is manual trans there may still be a differance between the year models for the start circuits.

cartune777

so i just have to hook a wire to the syarter and then run it through the fire wall and plug it to the sta pin on the ecu? or do i have to do that, plus run the same wire to the 3.0 body harness?