Wiring for Non-Turbo 3SGE swaps into Celica ST204 is undocumented. Strange but true. As of today, we have two 6gc members (KAOS and mi645) attempting the 3rd gen 3sge swap with no information on how to wire them.

I understand that the swaps have been done and are not difficult. I’m starting this thread in hopes that those with the experience can answer some questions about these swaps. The details of the wiring all follow from one primary question.

Question: Is it best to use a 5sfe harness to swap in the 2/3gen 3sge?

(Reminder: 3sge means non turbo or na. Without a ‘t’ in it. Not 3sgte. Normally aspirated.This thread is about the 3sge, NOT the BEAMS. That is not a typo. Atmo. Strictly vacuum. Sucker not blower.)

Following are the threads and posts that lead to this question.

This was posted on here by 99gt3sge

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From eazy2001x on mr2oc:

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From user pimpm3 on mr2oc:
Sadly, the image of the wiring changes that he made seems to be lost on the internet. I tried waybackmachine. No luck.

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Open questions for anyone who knows:

Can the 5sfe celica wiring harness be used on a 3rd gen 3sge swap?
If so what changes must be made?
Is it simply an act of opening both ecus, looking at the printed diagrams, and matching them up?

The 3rd gen motor is supposedly the easiest to install but is the 2nd gen really any harder? Can not the 5sfe harness be modified slightly to run the 2nd gen engine and ecu? Again do the ecus need to be simply opened to reveal the key to matching a few pins?

Any info and thoughts appreciated! There are people out there right now trying to find this information! I know I have been asking around for weeks now!

yes the harness can be used, you might have to change some pins, is this a BEAMS 3S-GE? if so im sure this has to be covered. Batman has this info i believe

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This is about the non beams 2nd and 3rd gen motors in general. The beams is well documented thanks to Batman and Richee's efforts. Several other users have added to the knowledge as well.

The 2nd and 3rd gen motors however have relatively little in the way of how tos or write ups.

I know Czwalga did the swap and said it was very simple. Maybe he could contribute? I know the clutch start wire is in a different place on JDM Celicas, and mi645 just confirmed that on his swap. The BEAMS needs two changes in the EA1 plug- one of those is because the 5S uses a distributor where the BEAMS uses COP so the 3rd gen won't need that but the other is a ground. You'll want to compare your 5S harness to the 3S harness there.

Overall I think it would be easier to compare the two harnesses and make the few changes necessary to the 3S harness than try to make the 5S harness work. I'd bet all the sensors and plugs on the engine will be completely different, making more work to try to make the 5S harness work.

JDM Celica's don't have the 'clutch start' feature.
With richee3 on comparing the 2 harnessesssss together.

I have wiring diagrams and pinouts if it helps, plus can check my Celica if you're trying to find what wire goes where or vacuum hosing due to the ACIS system.

My harness was cut everywhere so I end up combining my 5sfe and 3sge harness. Also had to add 3 feet of extension to reach.

Generally it was pretty simple, but since mine was cut it made it more difficult, but wiring in general is easy for me.


If you have a complete 3sge harness, use it.

This post has been edited by czwalga: Dec 15, 2013 - 8:29 PM

the easiest wat to do this swap is to use the 3sge harness, only the wires follwoing the distributor need to be extened, and the idle ac valve wires. everything else reaches all you have to do is go through youre wiring harness unwrap everything and straighten all the wires out, the wites going to the ea1 plug from tr starter solenoid basically split them and retape tem away from the rest of the harness and make sure you use the factory shields rubning behind and the side of trans and engine. everything else basivslly works im even using 5sfe fuse box. i was missing 1 thing the pin connector that hooks to the idle ac valve wasnt with my harness, thats about it for wiring. im still trying to figure out how to wite my solenoid to start my car, havent touched it yet. but will ge back to u guys tomorrow.

The other thing you could do is get in touch with mr220v. He may have the wiring diagrams and tell you what changes to make for a fraction of what it would cost to have him make the harness for you.

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I talked to him about this a few weeks ago. He said that very little would have to be done but wasn't sure about it off-hand. We did confirm that the 3 ecu plugs on the 5sfe harness fit right into the 3rd gen ecu. Not sure what needs to be re-pinned off-hand.

Thanks everyone for contributing so far. Especially czwalga and mi645 for dropping in with the first hand experience.

I'm not sure if I had a different harness, but there was no way mine was fitting in the OEM location without extending the harness. It was made for RHD, so it entered on the complete other side of the firewall.

There's still connections that have to be made, to the body? harness. For the gauges, fuel pump, etc that sit right above the ECU in the stock location. It just plugs right in, but if the wiring isnt long enough to get there you'll have to extend them.


Like I said though my harness was really mangled, so I just pretty much made my own out of the two I had. I think the igniter colors were different? Buy the celica oem wiring manual for like $20. That along with the 3sge ECU pinout is enough to figure out what needs done no matter what harness you're using.

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I have done two 3sge non beams swaps, one of them i used the 3sge harness and the other i used the 5sfe harness.
first off, If you have the complete 3s harness then everything is basically plug and play. the things i had to do was remove the the plastics that cover the harness in the rear section of the harness and then it frees up some extra length which allows you to reach the the ecu plugs. aside from that i extended the ignitter and coil wires to reach the fire wall. and i also extended the intake sensor that goes into the air box. also there's one wire that is missing from the engine bay fuse box which i believe its for the airbag, it's up too you if you run this wire. this method is way easier than cutting the harness and extending it. and lastly since my car was an auto i had to jump the wire from the neutral safety switch so my car would start and wire in the reverse switch. other than that everything is plug and play.

The second swap i did i used the original 5s harness because the 3s harness had the fuse box wires cut off, and the dash plugs cut off. So i compared the 3sge harness and its basically the same lay out. first of all i sourced the ecu plugs form a s/c previa, it has the same plugs as the 3s. then i re-pinned the ecu wires to match the 3s diagram. now since this car was a federal car the injectors are wired a bit differently than a cali car. i basically had to to wire two injectors to the ecu plugs. for the reason that the 5s injectors share wiring signals. then i wired the acis solenoid to the ecu, i also wired in the 02 sensor. i used the two wires from the 5s 02 sensors and added one wire in. after that i laid out the harness on the engine and i had to make sure the plugs reached the throttle body and the sensors that go on the water neck. and also i had to re-pin the dizzy wires, there in different location. Basically all the plugs that go to the engine are the same as the 3s, after doing both swaps i preferred using the 5s harness due to the fact that the car with the 5s harness idles smoother than my car which is using the 3s harness.
over all since i have wired hondas, 2jz's, sr's this swap would have been easier if i had better wiring diagrams. but that my 2cents.

>>3S-GE Pinouts>>



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3S-GE Wiring Diagrams>>


Large version



Large version




Large version




Large version

Thanks mi645, czwalga, 99gt3sge and rusty for helping make this the most informative page on the whole internet about this subject!

well now i try to run the motor it idles so bad cuz the avis doesnt close after start up im guessing cuz i dont have the intske vaccum connected

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This post has been edited by czwalga: Dec 17, 2013 - 8:53 AM

lol czwalga, my issue was that my motor didnt come with oem box, im waitig on 1 coming in the mail.

you don't need a intake box, im runing a short ram intake

well i didnt have any intake system period but now i have a power enterprise hooked up all vaccum line, i will start it tonight again

We have mr220v do all our wiring conversions. http://www.wiregapinc.com/ He is reasonably priced and all you have to do is send him your existing engine harness and the 3sge engine harness and he will merge them to a plug and play solution. Saves a lot of down time!

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No doubt. I have been so frustrated and scared of everything that I have to do, that I've completely backed away from the swap for the last 6 months or so. :'(

Enough is enough, I'm back.

Thank you so much for starting this thread, how far have you come on your swap?

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Save's a lot of downtime, but what if you no longer have the original harness? He's quite costly as well, IIRC.

I do however have 2 3SGE harnesses, and was hoping to simply extend the wiring on the GOOD ONE - with the wiring from the OLD ONE in order to use the stock firewall hole. cwalga, this is how you did it? And it was relatively simple? It seems like a daunting task to me...

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This seems like the more feasible route. Would you happen to have any pictures or references to your "remove the plastics that cover the harness in the rear section (do you mean the section that goes through the firewall?)"

I'm using the 3SGE ECU as well, were there any pins that needed to get swapped on the INTERIOR cabin harness, or is it all plug in play from the ECU onward?

Thank you, 99gt3sge!




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All in all, I'm excited to get this project started again, and more importantly, FINISHED.

You'll probably see me spamming the boards with a plethora of questions over the next couple of weeks... apologies in advance.

This post has been edited by KAOS: Mar 27, 2014 - 11:57 PM

Next large task on my agenda:

Figuring out the axels. I was told at one point that we could just use the 5SFE axels in the 3S - which is all good with me, but what about the driveshaft bearing on the passenger side?

Meaning, will the 5S driveshaft work in the 3S bearing mount?

id ur using s54 everything will bolt onto the 3sge even the carrier bearing. only the e56 or e153 u need different components

Anyone make any progress on their swaps?

Anyone who lengthened their harnesses, how much did you have to lengthen it by? I'm thinking around 4 feet should do the trick, but I don't know...

Thoughts? Where did everyone go on this topic?

Whoa, easy! I extended mine about 2 feet and it was just a little bit too much. I'd rather have just a little bit too much than not enough.

I've heard between 18"-24" is ideal.

for what it's worth here's what I did for my 3s swap, not sure how this compares to what would be required for a beams harness:



Its extended by 42"


It runs around the clutch reservoir and along the firewall, suspended from the strutbrace, before entering the factory harness opening on the passenger side.

I have had zero issues with clearances or anything else like that.

If you're planning to do this be prepared to extend a coaxial cable, and to recreate some cable shielding. 3M sells shielding tape, but it's possible to make your own with a litte extra work.

This post has been edited by enderswift: May 15, 2014 - 3:20 PM

i didnt extend mine, i simply took all the factory tape off re routed everything tape it back up, put the shields on and thats about it, i only extended igniter plug wire and intake temp sensor.
didnt touch the evu plug side. pretty simple.

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Ok, I've taken the wiring harness apart as you said and you're right, looks like I can move the majority of the wires so that the harness will reach the stock ST204 firewall hole, and then just extend the ignition and temp sensors.

Did you change any of the pinouts at the fuse box in the engine bay? Or any of the pins at the ECU? Or was it all plug and play???

This post has been edited by KAOS: May 27, 2014 - 11:35 AM

everything is plug and play, and yes the harness reaches with no problems just make sure u put new shield and wiring tape for safety, and no u dont have to re pin a single thing if ur using the ecu that came with the engine and harness off the 3sge. if u need anything else let me know