View Full Version : Wiring Harness Swap Question

01-09-2014, 08:19 AM
I'm nearing a critical part in my swap, the wiring. I believe I've searched the hell out of the process of doing it, but I don't feel like I follow why the body harness needs to be messed with at all. Or is that only something you worry about when sending it into Tweak or someone? And one last question, would a USDM alltrac harness be plug and play if it it the same year as the car and ECU? My apologies for the bombardment of questions.

01-09-2014, 03:26 PM
You should come over this weekend at some point and we can try to do a little research on this, just because I have to figure out the wiring for the Vert's 5SFTE swap and I will be running into the same question.

If you havn't seen this thread, check it out. It isn't a sticky for some reason so you might have missed it.


As far as I can tell, there are a lot of connections that jump from the engine harness to the body harness (I think chargring and starting, etc... ).

01-15-2014, 03:02 AM
What is your old engine and year, and what is the new engine? Typically you just have to deal with the engine control harness.

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01-15-2014, 01:48 PM
1990 5sfe will be getting taken out and replaced with a 1990 3sgte.

01-19-2014, 03:40 PM
I would personally do it this way. Take the 3sgte harness apart, move the wires such that the part that goes through the firewall is on the other side. Most of the wires on the harness are actually long enough to reach just fine. Then re wrap the harness and install. The body harness comes into play because the 3rd plug on the ecu comes from the interior and not the engine harness. So just compare the pinout diagrams for both ecu's and switch around any that are necessary. I think it's only a couple wires. Everything else will pretty much plug right in.

So that's how I'd do it. Your swap is one of the most straight forward so don't be afraid. There are people here who have done it and can help you along the way!

Any questions, just ask.

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01-20-2014, 06:42 AM
save ur self some time and buy a pin out tool for the harness. i drilled a hole on driver side and ran it thro to pass w no problems. it also helps to print out both diagrams and cross reference n document what ur doing..

or hit up dr tweak for a harness patch

01-21-2014, 05:28 AM
Thanks for the feedback. I just bought a harness today, so I'm going to see what all I have to do once I get it.

01-28-2014, 02:48 PM
seriously to make that run its super easy.
12v all the time
switched 12v
warning light
fuel pump

Heres how I wire things up
hook up the 12v stuff
hook up the warning light
turn the key to on and make sure the w light comes on, if this light comes on the ecu is happy and turned on
then hook up the little things, tach, spd, ac if you want it. etc.

Honestly the car will run with just the 12v applied and the fuel pump jumped

Before you crank it though take a multimeter and make sure the injectors have 12v and the ignitor and coil have 12v (black and orange wire) when the key is on. If you must jump the fuel pump and fire it up.

I always prime the turbo before hand by pulling the coil plug and holding the starter until you see the oil pressure light turn off, this makes sure the turbo got a little oil in it to keep the bearings happy also it helps the engine from starting up dry.

01-30-2014, 06:53 AM
I received my harness. Its all there aside from a few unmentioned chewed up plugs and two cut wires around the alternator plug...Wasn't exactly thrilled but what can I really do now? Everything else seems to be there. I have went through and started labeling what each individual plug is. I have 3 or 4 I wasn't able to identify. I gotta put in some time researching for those, so we aren't playing the "guess which plug this is" game. Also, thank you andy. having a general list of things that need done, as opposed to staring at a bundle of wires and saying, "Well shit."