Wiring help please!

[91mk3]

I have a 1991 n/a supra that I swapped a 1991 turbo motor into. The motor I bought has a harness that is cut up by the ecu plugs.

Here is the ecu end of the '91 harness that came with the engine:

It is missing these plugs:

I bought the ecu end of a late '89 harness. Both have grey plugs. I was planning on just matching up the wires and just splicing each of the wires. Tedious, but it should work. I matched up almost all of the wires:

Now I have these 3 wires remaining from the '91 harness that came with the engine:

And I have all these wires remaining from the '89 harness:

The group of wires on the left come from this white plug:

What is this white plug for? Was it only an '89 plug? It doesn't make sense that there are no wires coming up from from the rest of the '91 harness that match any of the wires on that plug. Anyone have any ideas? I appreciate any help.

Thanks,
Dan

 

[SideWinderGX]

As I've been tracing down a few wiring woes myself (wondering why my temperature gauge doesn't work...I think I hooked the wire up to the wrong connector on the thermostat housing haha) the ONLY way you'll be able to figure out what is what is by using the TEWD. Find exactly what wires are for what on each connector and match them up. Honestly there isn't an easier way, and heck you might even find a few wires you made a mistake on.

 

[ForcedTorque]

89 and 91 harnesses are not created equally. I converted an 89 harness to work in my 92 with the help of others in a thread that can be found by clicking on my username, and then "search forum threads" (top of page 3). There are diagrams in there that should help you. It is a bigger nightmare than you have discovered yet! There are differences due to the addition of the air bag between those years.

 

[grimreaper]

Start printing the TWED.. At each connector on the diagrams, it will list a letter (a,b,c etc..). At the back of each section that letter will correspond to a picture of the connector.
This is going to suck but I would lay out the harness and system by system go through it and make sure everything is where it should be. Matching wire color up from different year harnesses is a gamble that its all correct!
You could buy a new harness for $500 +/- as well. Or a decent set of ratchet crimps, strippers and a bag full of uninsulated crimps with heat shrink and sealant can be had for far less.. I'd rebuild the whole harness with new runs of wire but then again i like torture and headaches

 

[toyzforme]

I just did the same thing as you, I dropped my 89 Turbo into a 91 NA shell and it was a wiring nightmare. I am still trying to figure out my door lock and window issue. Other than that I got everything working. Like everyone else said already, get the TEWD and start tracing wires. It is a pain in the A$$, and not what you wanted to hear, but it is the only way. Take your time so as not to make a mistake

 

[shaeff]

I don't know why you guys bother. Just find an engine harness (turbo or N/A, depending what your motor is) that matches the year of your chassis. Then it's literally PnP. I'll never understand why people cut/splice etc.. to make them work. That's so many more possible failure points, in my opinion. I honestly wouldn't bother, and I actually enjoy wiring.

(regarding my PnP comment before someone jumps in: some of the t-stat area connectors would need to be changed depending on year, and if a '92 model, possibly the knock sensor connectors but all in all, much easier to find a harness that's designed to work with your chassis)

 

[SideWinderGX]

Hmm crap, I didn't state that in my post...

I'd much rather run a new wire and pin/crimp new plug in terminals than cut and splice. Cutting and splicing is literally on the bottom of the list, looking at my harness and how much of a pain in the ass it is thanks to heat and previous owners. Doing it the right way (or getting a working harness) is the best way to prevent fiddling with it in the future.

So, yeah, shaeff is right, thanks for bringing that up.