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The subaru of many acronyms
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Its essentially the method for any subaru wiring merge. All you want from the donor harness is the part that goes from the ecu to the engine, anything else that leads off towards the dash etc can be cut to be merged with your existing harness. You do the same method on your current harness, extracting the ecu to engine portion that you dont want setting it aside and sorting out the similarities between the two harnesses.
 

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Im considering a swap on my gc8, ive done swaps on other cars and I was just wondering why its necessary to cut and solder wires instead of repinning the connections at the ecu?
 

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www.jackstalk.com
‘98 RS, '00 911 Cab, '18 CT6 TT, '04 Escalade ESV
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5,518 Posts
Im considering a swap on my gc8, ive done swaps on other cars and I was just wondering why its necessary to cut and solder wires instead of repinning the connections at the ecu?
It's easier and not all the wiring connections are done at the ECU. There's a bunch of wires you have to connect elsewhere going toward the SMJ and engine fusebox.
 

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Experimenter
Tubaru Pickup
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3,913 Posts
lil bumperoo. Just finished up my wiring but have a question/concern. On my 98, the red 5v sensor with coming from the dash has 5v with ignittion on, the blue 5v sensor wire from ecu has 5.7 volts with ignition on. Brydon said these should be tied together, is this true??????



At this point you actually have to put on your thinking caps. This red wire is Sensor Power Supply WRX B135/9 – RS B136/15 ... This wire branches into three wires. One wire goes to the ecu, one to the RS engine bay, and the other to the bulkhead of the RS. The WRX has the same thing but you have to think about what you need. If it goes to the RS ecu then you can cut it. Same goes for the RS engine bay. What ever this powers on the RS engine wont exist once you have a WRX motor in there so cut it.



On the WRX side you have the same three branches but only one is cut. The one that know needs to lead to the RS bulkhead harness. Splice this in at the junction.
 

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MY99 OBS
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I'm confused, what ecu is being used after merging the 2 harnesses? I also have a question. Would it be possible to run 2 ecu's? Leaving the rs harness alone and just running the wrx wires to the wrx ecu?
 

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I ❤ BOOBIES
99 Coupe
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Your using the turbo ecu, and theres no point in keeping two, theres no space and the old ecu wont be doing anything at all it will just clutter everything up.
 

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01 RS Sedan
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Great writeup. I'm nearly done with my merge but my injectors are only getting around 6v instead of 12. Is this a result of a bad ground? regardless, run it by me like I'm stupid and seeing it for the first time, it's been bugging the heck out of me. Thanks.
 

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I ❤ BOOBIES
99 Coupe
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17,029 Posts
I wanted to post a wee update to this, obviously photobucket broke the internet but thankfully someone hosted the photos and text which is linked in the first post. Im currently working on a web series called Project Car, the name speaks for itself, the first few episodes are going to be DIY/How-to based and will consist of this entire wiring guide in video form with as much step by step help as i can give. I filmed a good 3+ hours today and will be filming the entire swap process for my new car. And before winter i have 2 more swaps to do, so ill make mini videos to address the few differences in wiring between year/model swaps.

Once i can get some of the footage together ill post it here and i want everyones thoughts on anything i can do to improve it.

 

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I ❤ BOOBIES
99 Coupe
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17,029 Posts
Ill also add that i have every single service manual from 1990 and up in good quality PDF's so if anyone ever needs info or wiring diagrams or pinouts just PM me. Once i get everything together and organized ill try and find a spot where i can have all the files accessible in one place. Im also condensing Brydon's pin out guides into one excel sheet and nice and neat, some of his stuff is spread across a bunch of forums and whatnot. Its a lot of work so its going to take some time.

North Ursalia also has quite a bit of stuff hosted on his site, but a lot are old scans of paper diagrams and things like that, so im hoping this will be helpful to everyone.

Added: So this ended up blowing up big, i have like a 12-15 page guide with a bunch of swaps that include everything from pin#'s to wire color, pin outs of connections, immobilizer units, pump controllers etc. Im almost done with the GD engines, just have to go through colors and then sort everything so its nice and neat. Ill eventually make it a PDF that anyone can download and print, but i probably wont be done for a few weeks at best.

Ill also do what i can with hosting the guide as well as service manuals for US cars. And im working on finding correct JDM EJ20G/K ecu diagrams and will work on those too for an addition to the guide.
 

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I ❤ BOOBIES
99 Coupe
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17,029 Posts
Question:

For people who have already done merges, what were the areas of the process that you had issues with? What information did you need to reconcile the issue you had?

For people who have NOT done a merge yet, what part of the process do you find the most difficult/intimidating? Do you have access to factory wiring diagrams/pin outs?

I have a 01 OBS swap im about to work on but the harness is being sent to Zephyr so i wont be able to document it, however the vehicle disassembly and whatnot will be. Once thats done i can get my new car in the garage and start that again and continue filming the merge process.
 

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Well I got a few questions. I got a 2000 rs25 that I am swapping a 02 wrx wagon motor in. I got the wiring out of the wrx and the wiring out of my rs. Got all of the wires in the guide hooked up but I have wires on the wrx harness that dont go anywhere. What have I missed? I also have a few wires at the rs computer that are still hooked up.

Still on the RS harness
B136/29
B136/16 <this runs to the ground connector and has a blue wiring coming from it

Loose wires on the WRX harness
B134/18
B134/19
B134/13
B136/15
B136/14
B137/23

Also has the blue/white stripe that is on the ground connector on the wrx harness

I probably cut something I was supposed to when cutting the wrx harness up lol
 

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Cheap Kitchens
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1,898 Posts
Question:
For people who have NOT done a merge yet, what part of the process do you find the most difficult/intimidating? Do you have access to factory wiring diagrams/pin outs?
I have access to all factory diagrams and I print them out to write notes as I work on different connections. My swap "merge" is very atypical though...

I have a complete harness front to back from the donor vehicle and of course complete harness in the shell vehicle. There was a lot more in the donor harness that I wanted to add to my shell so I went against the current and, instead of merging the harness at the ecu, I installed the complete donor harness in my car and started to connect each body function individually.

Knowing what wire needs to plug into what is only a small piece of the puzzle and the diagrams/color coding make it really easy to understand the individual circuits and their functions. I have no problems understanding what I need to do just making it happen. I've written lots of notes and have all the door wiring sorted and labeled so it can just be crimped back together when I am ready to wrap the harness back up

Finding how to lay the harness in the car so the wires can be cut to length is where I am at currently. I got the firewall grommets swapped over and installed but the harness is still unwrapped and wires everywhere. seeing all that wire is certainly an intimidating sight and when people see it their eyes get huge, it kind of stresses me but I just focus on one thing at a time.

The most difficult part for me is seeing the big picture, while it's easy to focus on window switches or on the wiper circuit, it is harder to see the sum of all the parts and picture how it all fits together. My fear is that working on the corners of the puzzle will put me in a spot where I have to rearrange the big pieces I have worked so hard putting together to make them fit together.

Moving forward my direction is going to be bundling the wires with twist ties and checking lengths for optimum connection locations. The list of things that need to be connected is quite large and I feel like working at the ecu would have been much simpler but my urge to be different got the better of me and I now have to push forward with this idea right or wrong

It's almost like a body swap instead of an engine swap the way I'm doing it and I'm curious if there are more splices at the ecu or the body. I could total them up but off the top of my head I just know the circuits I have to connect

Starting front to back;
1 Headlights, corner lights, turn signals and fogs
2 Horn, A/C compressor and front wiper
3 Mirrors, windows and door locks
4 Climate controls and interior interior lights
5 Instrument cluster and clock
6 Rear defroster and rear wiper
7 Tail lights, turn signals and plate lights

Also of note I am converting from auto climate control to manual so that is way more work, stripped out srs along with other stuff I won't be using too. A few connectors are the same and a lot are same wires but different connector. In hindsight I would not recommend this way of doing things but I wanted to try it and I'm sure I'm making it more difficult than it has to be
 

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I &#10084; BOOBIES
99 Coupe
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17,029 Posts
Yeh thats honestly way harder to do than the normal process for a merge. You have to change a ton of connections, wire lengths, pins etc like you mentioned, all over the car. With the normal merge you only have a handful of wires all in the same exact location. Ill mention it in the guide
 
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