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Thread: 02 wrx swap into 98 outback

  1. #1
    "FNG"
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    02 wrx swap into 98 outback

    its been awhile since ive been on this forum since the lack of having any subarus. but i recently have acquired a 98 outback with a blown ej25d and 4eat autotragic that is questionable the car was 150 and its a limited with the twin sunroof and power heated leather blah blah blah. Now today i have bought a ej20t with everything including short engine harness no pcm or harness to pcm but it did come with turbo intercooler piping and that stuff, again i cant complain it was only 200 for a good running engine.

    Ive been looking around the forum and i understand the engine harness has to be merged and east coast swappers or suby king could do plug in harness for around 900-1500 which is a lot of money but im not sure why a whole harness would be needed to spliced.

    Im just lost on what is needed to swap a wrx motor wiring wise.

    Ive ruled this down to a couple ideas that make sense to me but im not sure what is the actual way this needs to be done

    1) merge the whole wrx harness so things like radio and lighting power seats and sun roof etc still function.
    2). find a wrx pcm and use that ? but would that plug into the outback harness? probably not.
    3) either find a programable pcm that is for an outback (from what i read cobb or aem doesnt make them for an outback) so possibly flash the current one in it to work?
    4) get a wrx pcm and harness to connect to the motor and ecu. and figure out how to get gauges to work through schematics.

    Again this is just brainstorming. i dont know which one is the right way to do it i just find it pointless to spend at least 900 on a harness because im more than capable of completing a task like this by just reading diagrams.
    1998 legacy outback 4eat 202,000
    1999 legacy outback 5mt 165,000

  2. #2
    SLi Lurker nepbug's Avatar
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    PCM = piggyback?

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    SLi nOOb Alphius's Avatar
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    PCM, ECM, ECU, all the same.

    PCM = Powertrain Control Module, mostly a GM and newer car term
    ECM = Engine Control Module
    ECU = Engine Control Unit

    Check out my thread for lots of good WRX swap info. Don't miss the link to the Google Docs spreadsheet wiring info.
    https://sl-i.net/FORUM/showthread.ph...I-6-speed-swap

    With a USDM 02-05 WRX engine, the best option is to merge the WRX ECU stuff into the Legacy harness. Then you get a fully tuneable ECU. There are services to do it for you, but not too difficult with access to the factory service manuals and some wiring knowledge. I did mine myself.
    99 Legacy GT WRX - Now for sale!
    05 Legacy GT Limited 5MT Wagon - Stock-ish.
    02 Outback Limited 5MT - Lifted, Dual Range
    84 Camaro Z28 - LS1/6-speed
    85 Silverado - Low and slow tow rig

  4. #4
    "FNG"
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    So does that mean the two Ecus have the same plugs on them? If so would a "merge" just be a matter of depinning the connectors so they have the right sensor going to watch pin? Or am I wrong there and need to change connectors too?
    1998 legacy outback 4eat 202,000
    1999 legacy outback 5mt 165,000

  5. #5
    SLi nOOb Alphius's Avatar
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    In very simple terms, you will take the Legacy dash and front harness out and cut all the engine related stuff out of it. You'll take a WRX dash and engine harness and cut all the body stuff out of it, leaving only engine controls. You'll then combine the two, and join the appropriate wires between the WRX engine controls and the Legacy body harness. In the end, you'll end up with a factory-looking harness that has all the Legacy body systems while being compatible with the 02-05 WRX engine.

    The ECUs are not even closely compatible, and neither ECU will run the other engine at all. The cam and crank trigger patterns are completely different between the two.

    If you read my thread there's more info, along with pictures in a good overview sort of way. Here's the link to my wiring merge spreadsheet.
    https://docs.google.com/a/thecornman...it?usp=sharing

    Also check this guide out for more pictures of the harness merging in a step-by-step sort of fashion:
    http://www.rs25.com/forums/f128/t141...e-harness.html
    99 Legacy GT WRX - Now for sale!
    05 Legacy GT Limited 5MT Wagon - Stock-ish.
    02 Outback Limited 5MT - Lifted, Dual Range
    84 Camaro Z28 - LS1/6-speed
    85 Silverado - Low and slow tow rig

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