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How to modify a stock EJ20T wiring harness
Xeique - November 7th, 2010 at 12:14 PM

Does anyone know what I can get away with cutting out of the stock 2004 WRX EJ20T harness? Or better yet has anyone done a write up on how to do this?

I am putting the EJ20T into my 1973 vw bug (non-super). I will be using the stock wiring harness and ECU but am loving sorting through the thousands of wires. :crazy:

I assume I would need all of the following. Correct me if I'm wrong or missing something.

-all wires coming out of the ECU
-most of the fuses
-main power going into the fuse box from the battery
-all of the engine loom and its connections to the main harness on to the fuse box
-all of the loom coming from the engine harness to the ECU
-OBII port connector but I'm not sure what that looks like (For reprogramming the stock ECU)

The rest of the harness looks like it goes to the rest of the car like doors, window controls, etc...

I have all the factory wiring diagrams and info on the car including the whole factory manual on CD if anyone has the same model and needs some info.

Any help would be awesome,
Chris


Lovebuggy - November 7th, 2010 at 03:00 PM

Just send the loom to AMauto in Noosa. For the sake of a couple of hundred dollars it is well worth it. They will return a stripped out loom with tags of what wire needs to connect where to integrate into your existing loom.


STIDUB - November 7th, 2010 at 04:27 PM

:tu: as above :tu:


Xeique - November 7th, 2010 at 06:45 PM

I have the harness sitting on the bench and didn't really want to send it out to have it done. I also don't have the extra cash.
I live in the U.S. so that doesn't help much either.

I've done extensive searching on this forum as well as shoptalk and haven't found any specific info on modifying the suby harness for a bug. I'm hoping someone has done this themselves and has some pointers they can give me.


Joel - November 7th, 2010 at 06:50 PM

Hope you got the key transponder and immobilisor module, late model ones like that are pretty complex, most people end up going aftermarket management, alot easier to setup


Xeique - November 7th, 2010 at 07:13 PM

I did get the security module with the harness. I got all the harnesses, relay/fuse boxes, ECU, security module, and a few other components I wont need like the Air bag control unit. I didn't get the door harnesses or the rear hatch harness. Hope that wont matter.

I believe the key creates a B+ circuit with the security module which shouldn't be too hard to deal with. I'll have to double check the wiring diagram to make sure.

Chris


pete wood - November 7th, 2010 at 08:15 PM

dude this forum is in the wrong country for you. have you tried the "conversion perversion" forum on http://www.shoptalkforums.com/  ? someone in your neck of the woods should be able to help you.


Lovebuggy - November 7th, 2010 at 08:21 PM

I think you will also need the fuel pump control module which sits next to the fuel pump.


seagull - November 8th, 2010 at 12:14 AM

+ 1 for shop talk


Xeique - November 8th, 2010 at 09:33 AM

I've posted the same question in shoptalk with 17 views and no replies. I'm trying to ask as many people as possible so I can hopefully save some time and effort.

Lovebuggy - I grabbed the fuel pump, module and whole sending unit out of the gas tank.

I have all the wiring diagrams and can sort through each wire and figure out exactly what I don't need but it would be easier if someone knew the few wires i did need so I can isolate those and cut out the rest.

I have the harnesses all plugged into each other. The fuse boxes are connected and the motor is plugged in. I'm looking at the rest of the wiring and thinking I might be able to cut out most of it but don't want to miss cut and have to sort out patching things back together.

I think there are many people that would like to be able to do the wiring themselves but there doesn't seem to be much info or resources for them. If I can't find any info I will work through the wiring myself and probably do a write up outlining exactly what is needed and what you can toss. I know the EJ20T is a motor many people would like to put into their bug so the write up should be useful.

Chris


pete wood - November 8th, 2010 at 10:02 AM

there are lots of options for the EJ20T that is true. Can I put this option to you though, there are literally scores of aftermarket ECUs that are offered as plug and play options that motor in every guise. It might be easier in the long run to buy a good quality aftermarket ECU and go that way if you can't find the info you need. I would especially urge you to consider this if you are thinking about about serious turbo/injector/intercooler mods into the future. The factory ECU is very good, but if getting it to work is going to cause too much bother, just sell the parts on Ebay and go aftermarket. Sometimes I wish I had.


Xeique - November 8th, 2010 at 01:30 PM

Pete, I agree. If the Suby harness and ECU end up being a total waste and I can't get them to work I will probably put together a megasquirt system. I would rather go with the stock ECU and harness since I know how versatile it is. I have quite a few friends with suped up subaru's and have worked with them on tuning and mods for their cars. The stock ECU has the ability to learn and by using it I can also do typical upgrades like bigger injectors and turbo. If I do this there are plenty of maps available already for those setups.

I will keep going with the stock harness and ECU until it proves to me that I have to spend more money to buy another engine management system.

Chris


Adsman - November 8th, 2010 at 09:56 PM

Also to note that since he is in the US he will have some different wiring and vehicle options fitted to us. As above try the us websites.


Hutcho - November 26th, 2010 at 09:04 PM

Mate, if you're super confident in how an auto electrical system works and you have the CORRECT wiring diagrams/service manual disc, work through it and you'll get it done. I did my 06 loom but I'm a sparky (if that matters) and had the correct Service Manual/Diagrams from Subaru.
I can tell you this, as mentioned, you'll need all wiring between the immobiliser, ignition switch/barrel and the ECU. Once you study the diagrams and service manual, it becomes clearer. It wasn't easy for me to do but I like a challenge!
As you're going to hear a lot, if I knew how long it was going to take me I would have sent it away to be done as it probably cost me 3 times more in labour than if I sent it in to be done professionally. In saying that, I know every wire and exacly how and why it works. It allows me to modify at my leisure down the track..

Good luck!

Steve