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Discussion Starter · #1 ·
Are all the EJ20 wire harnesses the same?

I have a JDM 95 EJ20G that I am going to attempt swapping into an Impreza 2003TS.
I have the ECU....no harness. Trying to figure out what and where to get one.

Thanks.
 

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Discussion Starter · #5 ·
That's extremely helpful aphex.
I have spent alot of time with the search function on nasioc and here and have yet to find very clear answers. Thus the start of a thread.
So chime in with some knowledge.
 

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2015 WRX+TE37ta
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There haven't been responses because you have a clear misunderstanding of how the engine and wiring work. You're looking to get it spelled out and spoon fed.

Asking a very general, non-targeted question is showing the lack of understanding which would lead to people being in over their heads.

Contact a vendor that does wiring merges and try asking them. iwire, ecs performance, Broken motorsports
They're here and provide a good service to the community.
 

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Discussion Starter · #7 ·
If I knew the answer, I wouldn't be asking questions.

"Are all the EJ20 wire harnesses the same?"

I dunno...That sounded pretty specific to me.

"Why CANT I use an 02-05 EJ205 ECU on a 92-96 EJ20g?"

Hmmm...didn't think I was way off on that one either.

In over my head? I would definately say so if I WASN't asking questions and trying to understand.


Basically I haven't found anyone that has done this...but I dont believe it can't be done.

I will try one of the vendors.
 

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97 L, 13 WRX
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While im at it....
Why CANT I use an 02-05 EJ205 ECU on a 92-96 EJ20g?
You can. But that doesn't mean it's worth doing. The major difference is the crank and cam triggers are totally different between the engines. Also the IAC valve is different and cannot be used on the other ECU. The IAC also mounts differently, which makes it harder to swap to a WRX ECU.

I can tell you that the 02-05 WRX harness is different from the EJ20G, but I don't know that much about the EJ20G harness to know how different. If you are thinking about getting a 02-05 WRX ECU to use with the engine and ECU you have, then I would suggest not doing that. It will be a lot of work and not worth it unless you have a lot of spare time and you get the parts for free.

I would suggest finding out if there are different variations of harnesses for the EJ20G and find the one you need.

:facepalm:
Really? That's not a great way to treat a new member that you know nothing about.
 

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Discussion Starter · #9 ·
The reason this all comes up is because if I did the swap outright and merged the proper 20g harness with my current 03 harness and used the JDM 95 ECU everything would work fine....BUT it would not be OBDII compliant....so inspection FAIL. (2003 chasis)
I heard that you can swap the USDM 205 heads on and change to the USDM Intake manifold (which is not a direct bolt on) and possibly run the 205 ECU. But need more info on that.

Although the triggers are different, wouldn't the signal be the same?
So I would just have to rewire the harness' to compliment the trigger's signal.

The 20g had two variation in the WRX alone...92-96 and 97-98...
So there are really only two harnesses I am looking at here. (keeping out the legacy and forrester)

The reason I thought the USDM wrx EJ205 ECU would be a good fit, was because it is a COP system as well, same 8:1 compression, and OBDII compliant.

The process for wiring (if it would all work) would end up being a UDSM ej205 ECU to SAME harness--to 2003 TS harness--to EJ20g harness--to engine.

My easiest route would be a stand-alone or JDM ecu for wiring...
I just wish there were stand alones that were OBDII compliant.
(hondata has the ability to send and OBDII "ready" signal)
And a piggyback wouldn't work unless I solve the USDM 205 ECU issue.

"If you are thinking about getting a 02-05 WRX ECU to use with the engine and ECU you have, then I would suggest not doing that. It will be a lot of work and not worth it unless you have a lot of spare time and you get the parts for free." - bubba

Are you implying using two ecus at once?
 

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97 L, 13 WRX
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The reason this all comes up is because if I did the swap outright and merged the proper 20g harness with my current 03 harness and used the JDM 95 ECU everything would work fine....BUT it would not be OBDII compliant....so inspection FAIL. (2003 chasis)
I heard that you can swap the USDM 205 heads on and change to the USDM Intake manifold (which is not a direct bolt on) and possibly run the 205 ECU. But need more info on that.

Yes, you can bolt WRX heads on the JDM block and use the WRX intake manifold. But then you pretty much wind up with a USDM WRX swap, so why not just buy a newer swap in the first place?

Although the triggers are different, wouldn't the signal be the same?
So I would just have to rewire the harness' to compliment the trigger's signal.

No, the trigger wheels are different so the signal is different. I shouldn't of left out the wheel part in trigger wheel. I'm just stuck using megasquirt terminology. If you use the USDM heads this obviously wouldn't be a problem.

The 20g had two variation in the WRX alone...92-96 and 97-98...
So there are really only two harnesses I am looking at here. (keeping out the legacy and forrester)

I cannot agree or deny because I don't know much about JDM wiring, I would get a confirmation on that if I were you.

The reason I thought the USDM wrx EJ205 ECU would be a good fit, was because it is a COP system as well, same 8:1 compression, and OBDII compliant.

That is true, but there is a lot of work involved in the idea you have.

The process for wiring (if it would all work) would end up being a UDSM ej205 ECU to SAME harness--to 2003 TS harness--to EJ20g harness--to engine.

Yes, and that is a lot of work and research involved in that. Pretty much twice the work of a normal merge.

My easiest route would be a stand-alone or JDM ecu for wiring...
I just wish there were stand alones that were OBDII compliant.
(hondata has the ability to send and OBDII "ready" signal)
And a piggyback wouldn't work unless I solve the USDM 205 ECU issue.

Your easiest route would be to sell that engine and buy a OBD2 compliant swap.

"If you are thinking about getting a 02-05 WRX ECU to use with the engine and ECU you have, then I would suggest not doing that. It will be a lot of work and not worth it unless you have a lot of spare time and you get the parts for free." - bubba

Are you implying using two ecus at once?
No I am not implying that.
 

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Cluster Specialist
1999 Impreza RS - WRB
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BinaryDriver,

First, welcome to RS25.

Second, take whatever you know about Honda swaps and throw them out the window. You cannot simply swap manifolds and make some minor wiring tweaks with Subaru engines like you can with Hondas.

Third, sell that EJ20G swap. Simply going for any "JDM Swap" in a Subaru doesn't cut it. The absolute headache that you are going to have to endure in trying to make this swap work will not be worth the end result. If you want OBD-2 compliance, which tells me that this is a daily driver/road-going car, you have to pay the price for it.

To try to make your "swap attempt" work:

For starters, you would need to get an EJ20G ECU wire harness, an EJ205 ECU Wiring harness...and then you would need to match ALL of the plug wiring on both sides of the ECU harnesses - EJ20G on manifold side, EJ205 on ECU side. Be prepared to find that the 205 harness has more items on both sides than the 20G. Also, you may find that there are items that were 2 or 3 wires on the 20G harness may be a single wire on the 205 harness. The EJ20G does not have a fuel pump controller system. The EJ205 ECU, however, will look for one. The EJ20G and EJ205 use different coils, too.

Then...after that, you're going to need to swap out the cam and crank wheels and sprockets to the 205 - completely different trigger pattern and timing. You might find that these won't fit. So now, you have 2 choices: Attempt to find a way to mod the heads to make them fit (may require LOTS of customizing work, like using 205 cams...and those don't fit 20G heads) - that won't be cheap (assuming the shop doesn't look at you like you've asked for D15 swap in an RSX), or buy 205 heads. Your next headache if you buy 205 heads will be the 20G manifold no longer fitting. So you can buy a 205 manifold to fix this issue, but now if you've modded the harness for the EJ205/EJ20G hybrid setup, the harness will not work.

Your swap nightmare does not end here. Assuming you managed to somehow get the 20G heads to accept everything that is needed for the 205 ECU to get it to start its own cranking process, now you'll need that multimeter, because it may not start. The engine may be looking for a specific ground where the ECU expects a 5v feed...or 12v burst. Or, thanks to design changes, the sensors are sending info that the ECU cannot read correctly. Good luck getting the new sensors to fit. And, that throttle body...

Your heart is in the right place. However, this sounds like the plan wasn't well researched before you started getting things together. We can go on for a long time here about this.

Get an EJ205 swap and wiring harness. Then you can simply pull your harness out of the TS and put the WRX wiring in without modding it.
 

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First off dont listen to anything anyone has posted besides BinaryDriver & Wannabe Wrx. You have a 2.5RS which im happy i did not get because its OBD2 and heavier, I have a OBD1 basic Brighton. I have a 95 Ej20G sti ver 2 motor and tranny and i can tell you that it is possible to find a harness. Took me 3 months but i got the complete bulkhead & engine harness(that is now sitting in a box). Anyways find member RB2B. He might be able to find you one if he is still in Japan. I traded him a super rare maxim work equal length twin scroll header.

1) They will tell you to find a legacy engine harness which is bullsh*# and just as hard to find, plus you have to re-wire it.
2) They say you can get a stand alone and make your own harness which i dont know anything about.
3) Iwire rarely has harness bits for EJ20G's so if you call him he most likely wont be of help.
4) There was a site that offered new subaru harness's for a ridiculous price but Subaru stopped producing the EJ20G harness so thats also out of the question.
5) They will tell you to just find a vendor but its not that easy. You can try inquiring different sites with emails like I did but most will charge at least $1500-2000 for something they dont even know how to find.
 

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First off dont listen to anything anyone has posted besides Wannabe Wrx.
Umm, who are you to say who to listen to? Judging by your join date and your post count it doesn't seem like you've been around long enough to post something like that.

Mostly I speak for myself, but I haven't seen any posts that I would say "don't listen to them" about. If you don't agree with what someone posts then explain why or your opinion means nothing.
 

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Umm, who are you to say who to listen to? Judging by your join date and your post count it doesn't seem like you've been around long enough to post something like that.

Mostly I speak for myself, but I haven't seen any posts that I would say "don't listen to them" about. If you don't agree with what someone posts then explain why or your opinion means nothing.
Information and parts for EJ20G motors are pretty hard to find, "don't listen" is pretty vague to say but i have a EJ20G motor and tranny and i can tell you it was very difficult to find the wiring harness. My join date and post count don't mean anything to me. I was on Nasioc long before RS25 due to me owning a Wrx. When i got rid of the Wrx i moved to RS25 because i own a 95 impreza. I read more than i post. Every time i see a thread about a Wiring harness for a EJ20G its the same. either no useful posts or no post at all. He wants to find a harness and i told him where he could possibly find it, I didnt start on a crazy tangent. I gave him what i have found and my results.
 

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05 STI(WRB) 97 GF4(AG)
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anyway moving on to helping him and to the point...my ej20g has the rs harness (2000 2.5rs) and 20g engine harness(v4 wrx) merged and i have power fc for my standalone and when my other power fc comes back(thats right i have 2) im going to be selling the new one that i have because i don't need it so if u can find a 20g harness to merge with and u need an ecu and r looking for a standalone let me know. as far as the swap the electrical side of this car has been a headache and mines pretty much worked out minus the 02 sensor i have to rewire and the wire thats keeping the car from turning off by key :) its been fun but honestly being that ive had to source out parts from everywhere in the world(and thats not an overstatement) i think its going to be much easier on u to do a us wrx swap...i love my motor and its quick for what it has done to it but you'll find that no one around u knows anything about ur motor and the ones that do u have to talk to over the internet and sometimes u just want someone there next to u or maybe u just got tired of messing with it and either u give up or u want a shop to finish it...just something to keep in mind o and i have alotta manuels on the rs and 20g so if u need them ill email u everything i have
 
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