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1995 1.8L Impreza Coupe
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90 Posts
Discussion Starter · #1 · (Edited)
Hey all, I've been trying to find solid information on the ej18 vs ej20k (or G?) ECU pinouts. My '95 ej18 has a 3 plug connection (Ref. 1) with pinouts as seen (possible Ref. ?*). With the ej22t engine going in, I'd like to run the stock 1.8L ECU with a rrfpr as if it were an na-t swap; but I've also been looking into the Link G4 drop-in ECU for the 3 plug connectors (Ref. 2). I don't think that the ECU pinouts are the same between the ej18 and the similar 3 plug wrx ECU (Ref. 3), but most of the links I'm finding for the pinouts are broken. Does anyone have a current link for a 1995 ej18 ecu pinout that I could use for comparison sake?

Again, I'd like to use the stock ej18 ECU if easier just to test out the ej22t mechanicals before attempting any electrical swap; but I would like to make it more reliable with a tune later, if possible. Not scared of repinning the plugs as necessary, if I can find accurate references.

Thanks

References:
1. https://www.busaru.com/attachments/article/143/1994 Impreza ECM Pinout.pdf
2. WRXLink (3-4) - WRX4X
3. https://www.xcceleration.com/pinouts/Subaru pinouts/1997 ej20k jdm ecu wiring ver3-4.pdf
?*. Emanage Install on an Impreza L Part 1 – Unique Motorsports
 

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1995 1.8L Impreza Coupe
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90 Posts
Discussion Starter · #4 ·
The '95 ej18 was the L model, the RS didn't start until around '97 (I think). Standalone is great, if you know that the engine is mechanically sound. I bought this engine off craigslist, and don't know much about it, so I would like to drop it in and run it for a while to make sure the mechanicals are fine before buying and swapping in a standalone ecu. That way if I have a problem I know it's with the engine, and not something else. That's the plan anyway. I have the ej22t ecu, however it is a 4 connector configuration, as opposed to my 3 connector ej18 ecu. The other option is to repin the harness and plug in the ej22t stock ecu, then use the 4 plug Link standalone (which is another option).

I've noticed that a lot of the threads about ej18/ej22t swap talk about complete and/or partial wiring harness merging. That would be all well and good if I got a harness, but I only got the engine and ecu.
 

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'96 OBS
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350 Posts
If it was me, I'd either repin or make myself an adapter harness to. I think you should be able to find an ECU pinout in the Subaru Factory Service Manual: jdmfsm.info/ <- Pretty sure I saw a 1995 manual up there in the Impreza section.

Also, I generally find aftermarket ECUs to be less of a pain to troubleshoot than OEM ECUs. Aftermarket means having nice software on a laptop to tell you things like the ECU isn't seeing the trigger pattern it expects or isn't getting a reading from some sensor. It also gives you the ability to just turn on outputs to test them.
 

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1995 1.8L Impreza Coupe
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90 Posts
Discussion Starter · #7 ·
I didn't see anything in the 1995 impreza section of the jdmfsm.info/ for ecu pinouts.

Again, I'm trying to use the ej18 ecu if possible because I know it's functioning correctly off of the get-go. I don't know about the mechanical state of the engine that's going in, and I want to know it's quirks before going standalone; I don't need a mess of issues all at once. I'm just wondering if the 3 plug wrx ecu was the same pinout as the 3 pin ej18 ecu (unlikely) but I can't find the information necessary to be sure.
 

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'96 OBS
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350 Posts
I can almost guarantee it doesn't have the same pinout, but take a look here for the '95 1.8L ECU pinout: Subaru/Impreza/1995/WIRING DIAGRAM SECTION/Wiring Diagram/MSA5TCD95I19378.pdf page 25 of the PDF (says page 40 on the page itself). Anyways, there are some WRX manuals sprinkled in there as well (Subaru/Impreza/1997-1998/1997-1998 Service Manual.pdf is one. Wiring section starts on page 547 of the PDF). I still think you're doing things the hard way, but I'm hardly the one to cast the first stone so knock yourself out. :)
 

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1995 1.8L Impreza Coupe
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90 Posts
Discussion Starter · #9 ·
Ah man, you're right, I glanced right by that. I'll see if I can break them down and compare them here shortly, thanks!
 

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95 L, 96 OUTBACK
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2,904 Posts
I put a stand alone in my 95 L. I cut the OEM ECU connector off. Why bother making an adapter harness? If you do it right and remove the dash at the same time you can really strip the harness of unneeded wire and loose some weight. Plus you get rid of alot of the bulk in the factory harness making it easier to relocate the ECU. I put mine below the radio so I can see the blinky lights of the Mega Squirt 2 and access the serial connector without always having the cable connector or wired outside the ECU case.
 

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1995 1.8L Impreza Coupe
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90 Posts
Discussion Starter · #11 ·
Not looking to make an adapter. The factory subaru plugs match the Link standalone (Original post, Ref. 2). My question was weather or not I'd have to repin the factory ej18 plugs to match the factory wrx pinout. Which is looking like I'm going to have to.
 
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