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Old 03-01-2004, 12:00 PM   #1
Skidd
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Default Alternative to the Wiring Harness merge?

Ok.. I've been doing TONES of research into the WRX->GC conversion. (I have a MY00RS) I've been looking at wiring diagrams, and pin-outs between the 03WRX and an 00RS ECUs. It appears that most people do a merge of the WRX harness into the RS harness. And there seems to be little doub that it's a rather big job. However, I've been wondering if it's not possible to simply re-use most of the existing RS wires and pins, and just remap them?

Let me explain.
I put together a basic Spreadsheet with the WRX and 00RS ECU Pinouts side by side.. then did a comparison bretween what the RS has and what the WRX needs. It (not surprisingly) appears that MOST of wires needed to run a WRX already exist in the RS. From what I've been able to figure out, the only places where some sort of custom wiring would be needed is:
- Front O2
- Idle Air Control Solenoid
- Power Stering Oil Pressure Sensor
- MAP/MAF (Mostly the MAF)
- Tumble Valves
- EGT
- WasteGate Solenoid

If all other ECU pins exist, I was thinking it would be easier to simply remap the pins from the 00RS molex block, into the WRX molex block, then make sure the sensor molexes match.

Or, am I completely on glue with this theroy?
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Last edited by Skidd; 03-01-2004 at 02:17 PM.
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Old 03-02-2004, 10:18 AM   #2
mrbell
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I think your idea is pretty sound... unfortunately, it's pretty much what a "merge" is, I think. The one step you're saving is pulling the RS harness out. I think the reason most people go ahead and pull it out is that it's extremely difficult to track down which wires go where in the car so matching up the pins is where it gets difficult...
Then again, I've never done it and i'd be interested to take a look at those spreadsheets if you want to send them my way
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Old 03-02-2004, 11:17 AM   #3
Zephyr
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I'm also not sure if the pins on the plugs that go into the two ECM's are the same. You may want to check that out first before you start pulling pins. Honestly I think you are better off cutting and splicing only because then you KNOW for sure that they are connected to the correct location. The plugs are very small and confusing.

Z
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Old 03-02-2004, 12:26 PM   #4
Skidd
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Your right.. thats exactly what I'm tring to avoid.. having to pull the RS harness and needing a complete WRX harness. Technicaly, All I'd need is the molex at the WRX ECU, and any non-compatible sensor connectors that don't exist on the EJ25. If I can leave the RS harness in place, solder in a couple of new sensor connectors, and simply run a few new wires for the missing sensors, then I think it would be alot less hastle.

As for the pins in the harness itself.. your right.. I haven't looked at each.. so I'm only assuming that I would be able to pull the pin from one, and insert into the next. But if I can't, then I'll have to start cutting and soldering. Something I'm quite comfortable with doing. Perhaps even get my hands on the "Link Plus" wiring loom that CarModifications was offering at one time.

As for tracking down which wires go where in the car.. Perhaps I think it's easier than it really is? I figure, if pin XXX on the ECU goes to the SIGNAL-1 pin on the MAF sensor, then, looking at the sensor diagram, I should be able to track down what pin is the correct one.
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Old 03-02-2004, 12:46 PM   #5
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Oh the other thing that won't work is that the location of where the engine harness goes into the bulkhead harness on the RS and WRX is completely different. You'll have to add alot of wire to your RS harness.

Z
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Old 03-02-2004, 02:06 PM   #6
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Quote:
Originally posted by Zephyr250
Oh the other thing that won't work is that the location of where the engine harness goes into the bulkhead harness on the RS and WRX is completely different. You'll have to add alot of wire to your RS harness.

Z
Acutall.. I don't think so.. Not if my theory is correct.. that is because I'd be working with the connector to the ECU only. So.. the extra wires I'd have to add for things like the MAF would infact be extra wires.. but I would not hvae to go through the bulkhead harnes.. I can either just pass the new wires through the firewall, or even build my own completely separate bulkhead harnes..

P.S. as for that spreadsheet I build.. It was really just an easy way to put the pinsout for each ECU side by side, then one at a time, find it's match on each side, and identify what went where, and what did not have a match. Not really a complex spread sheet.
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Old 03-02-2004, 02:12 PM   #7
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ummm right if you say so. I've only done this enough times to know exactly what I'm talking about. The 3 plugs for the engine harness on the RS are right on top of the transmission right where the turbo would go. On the WRX they are located in two different locations. Two are located behind the battery and the last one is located on the passenger side wheel well where the boost solenoid is located. Your idea has merit in theory but it will not work.

Z
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Old 03-02-2004, 02:31 PM   #8
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I think you're missing what he's attempting Zephyr. He's saying use the entire RS harness on the WRX motor. Whole thing. SO instead of trying to hook a WRX motor harness to the RS chassis harness, you're hooking the RS motor harness to a WRX motor.
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Old 03-02-2004, 02:36 PM   #9
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Yes I understand that he is attempting to do that and it will not work. If you would like to prove me wrong be my guest. I think that cutting and splicing is by far easier and quicker. When I did my swap my car was down for less a day. I started cutting appart the RS harness Friday night and had the two harnesses married by about 2am. I had the car it self running and driving by 10pm Saturday night.

Your idea is great in theory but it is not practical. Not to mention it's gonna be alot more work.

Z
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Old 03-02-2004, 03:03 PM   #10
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I agree with Z. Your idea is good in theory Skidd you would also have to change all the wires in the SMJ too and probably lengthen them since the SMJ plugs are in different locations on the RS vs. the WRX. I don't have my WRX and RS diagrams in front of me so I can't go into much detail right now but you also have to remember that a lot of the wires branch off to some other sensors inside the bulkhead harness. Like on a 93 WRX the O2 sensor, wastegate control solenoid, pressure exchange solenoid, and purge control solenoid splice together inside the bulkhead harness. The injectors splice in with the fuel pump relay and main relay. I would definately be sure to follow every single wire coming from both ECU's in the diagrams and see when they split and where they go afterwards.

What makes most swaps intersting on the wiring side is almost every year the bulkhead harness is wired differently. If every harness was just 100 single wires running from the ECU to sensors swaps would be a lot easier.
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Old 03-02-2004, 04:03 PM   #11
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Ah, I'm with you now Z. From your last post i thought it sounded like you thought he was doing something else... bah, nevermind, I've forgot what I was even thinking... I ate too big of a lunch... I'm sleepy
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Old 03-02-2004, 04:08 PM   #12
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Quote:
Originally posted by mrbell
I think you're missing what he's attempting Zephyr. He's saying use the entire RS harness on the WRX motor. Whole thing. SO instead of trying to hook a WRX motor harness to the RS chassis harness, you're hooking the RS motor harness to a WRX motor.
Bingo.

Now.. either I'm missing something obvious.. or I don't really think Zephyr250 or Puck quite get what I'm trying to explain. My idea is to NOT touch the SMJ, the bulkhead plugs, or any of them. While I was reading the wiring diagrams, I just figured.. well.. lets say the ECU for the RS has it's Injector#1 signal wire at 134-4 and the WRX has it's Injector#1 signal at C-22, could I not simply map 134-4 from the RS loom to C-22 on the WRX ECU? And since It appeard that quite alot of the RS wires and sensors and the signals they provide (voltages, etc) seem to be the same as the WRX ecu expects, then it should not matter that the "Water Temp sensor" on the RS is routed through plug-A and on the WRX it's somewhre in the SMJ.. they both provide the necessary signal back to the ECU.

Or are you simply trying to tell me that where the harness goes through the firewall on the RS will physically be in the way of the WRX turbo? Cuz, thats a whole different ball of wax.

Granted.. I have NOT done a swap.. I'm still well into the research phase... so, all of my info is based on only wiring diagrams. If I'm wrong.. so be it.. I can live with a merge.. but thats not going to stop me from looking at all possibilities.
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Old 03-02-2004, 04:14 PM   #13
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Quote:
Originally posted by Zephyr250
Yes I understand that he is attempting to do that and it will not work. If you would like to prove me wrong be my guest. I think that cutting and splicing is by far easier and quicker. When I did my swap my car was down for less a day. I started cutting appart the RS harness Friday night and had the two harnesses married by about 2am. I had the car it self running and driving by 10pm Saturday night.

Your idea is great in theory but it is not practical. Not to mention it's gonna be alot more work.

Z
Woh.. really? a day! So.. the merge is alot easier than people are letting on? Some posts have stated that it takes some people more than 2 weeks just to do the harness. Others 20+ hours. This was why I wanted to try and find an easier route... 20+ hours sounds like a hell of alot of work.
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Old 03-02-2004, 04:28 PM   #14
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Yes my car was only down for ONE (1) day. Granted I did alot of prep beforehand to the WRX harness in the comforts of my basement to separate what I needed and didn't need as well as label it accordingly, I then made up a sheet with all the connections that had to be made from the RS and the WRX harness and went to town being careful to mark what had been done. Trust me soldering is alot easier than extracting pins. Not to mention that the RS engine compartment harness is shorter.

Z
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Old 03-02-2004, 05:16 PM   #15
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Listen to zephyr.
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Old 03-02-2004, 05:19 PM   #16
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you can always take all of the WRX interior/dash and use all of it's gauges/air conditioning stuff/ everything and just use it as almost plug and play... just a lot of cutting...
just do it the right way...listen to zehpyr
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Old 03-02-2004, 06:49 PM   #17
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Zephyr is also VERY good at doing this. AZP is on probably the 3rd or 4th swap maybe more (i can't keep track) If you had to do it yourself, 1st time, my guess is that it would take 2+ weeks on the harness alone.

-mike
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Old 03-02-2004, 07:04 PM   #18
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Well.. I guess i"m doing it the correct way then... Oh well.. I thought I might have been onto something... Never hurts to find out!

Thanx for you help guys!
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