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Some discoveries about OBDI EJ wiring


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12 replies to this topic

#1 Numbchux

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Posted 06 December 2006 - 03:45 AM

OK, I was helping a buddy swap an EJ22t into his OBDI legacy. We found that some OBDI legacy harnesses have 2 connectors between the body side harness, and the engine harness, and some have 3. These are the larger grey ones by the battery, they come from in the driver's side fender, and plug to the part that's integrated with the intake manifold.

First of all. in the 3-plug system. the smallest plug (should be 2 pins tall by 4 long) are ALL grounds. this was part of the problem with my origional install. I saw these grounds, but could not find that connector (my donor legacy had only 2 plugs). I later got another copy of the wiring diagrams, that looked identical, except when referring to these plugs. this diagram only had the 2 plugs, and showed the same ground wire cluster to go through the larger of the 2 plugs. instead of a plug of their own.

Here's what we found...and it doesn't look like there's a pattern based on year...

2 plug systems:
'91 FSM .pdf file
my '92 Legacy donor car
my buddies '91 legacy
my dad's '94 legacy wagon

3-plug:
'90-'92 Chiltons diagram
his '93 EJ22t donor car

what years do people here have, and what plug style? I'd like to be able to add a more comprehensive description of which systems can be found where to my write-up (given up on the Geocities page....just making a .pdf....)


ALSO. The engine harnesses are interchangeable. our solution to the problem above, was to use the engine harness from his 2-plug, N/A EJ22 in place of the 3-plug one on the EJ22t.

which also means that all the extra sensors required for the turbo (only a few, I beleive) get their wiring via the loom through the firewall. it also appears that wiring-wise. an upgrade from an OBDI EJ22 N/A to an EJ22t is VERY simple. just string a few more wires, change a few things at the ECU, swap ECUs. and go. This is VERY good news for me!!!!

#2 crash a-ron

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Posted 06 December 2006 - 11:20 AM

My donor car is a 1991 Legacy L n/a 2WD MT...definently 3 big gray plugs.

I just finished pulling the entire wiring harness last night, so I'm certain of it. What a pain in the rear. Most of the sensors (MAF, crank, cam, knock...) are on the harness that goes into the cabin behind the heater.

The only two I can't figure out yet are the VSS and the neutral sensor. What do I do with those??? The motor is going into my '87 GL carb wagon, so I don't think I have a VSS to hook up to...

BTW- Thanks to all of you that have posted stuff about this process. I only wish there was a comprehensive write-up like there is for the swap into a VW, and it looks like it is starting to happen!

Cheers-
Aaron

#3 Legacy777

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Posted 06 December 2006 - 12:53 PM

I think I can add some things.

The 90-91 non-turbo engines have 3 square connectors behind the battery.
The 92-94 non-turbo engines have 2 square connectors behind the battery.
The 91-94 turbo engines have 2 square connectors and 1 round connector behind the battery.

The engine harness is pretty much the same between the turbo & non-turbo first gen legacies. The only difference is the location of where the coolant temp sensor is. On the n/a engines, the coolant temp sensor is on the passenger side. On the turbo engines it's on the driver's side.

For my ej22t swap, I reused my 90 n/a engine harness, but just peeled back the tape and wire loom, and relocated the wiring connectors to the driver's side. Other then that, the engine harness remained the same.

As you mentioned, the turbo specific sensors come through the chassis harness from the firewall. I added the leads for those specific sensors, and that was pretty much all the wiring I had to do. At the ECU, I had to swap the positive pins of the cam & crank sensors because they are reversed for the turbo engines. In addition I had to unplug the mt/at identifier pin because the 92-94 n/a ECU's are wired backwards for some unknown reason.

#4 Legacy777

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Posted 06 December 2006 - 01:00 PM

My donor car is a 1991 Legacy L n/a 2WD MT...definently 3 big gray plugs.

I just finished pulling the entire wiring harness last night, so I'm certain of it. What a pain in the rear. Most of the sensors (MAF, crank, cam, knock...) are on the harness that goes into the cabin behind the heater.

The only two I can't figure out yet are the VSS and the neutral sensor. What do I do with those??? The motor is going into my '87 GL carb wagon, so I don't think I have a VSS to hook up to...

BTW- Thanks to all of you that have posted stuff about this process. I only wish there was a comprehensive write-up like there is for the swap into a VW, and it looks like it is starting to happen!

Cheers-
Aaron


Aaron,

You really need to find some way to get a signal to the VSS pin on the ECU. The ECU looks for a square wave signal from the VSS. Without it, the ECU will sort of freak out, and go into a limp mode. It changes timing, a/f ratios, and turns the cooling fans on. I had all these weird issues with the car when my speedo went out. So it's something you will need to find a solution for, or the engine is not going to run correctly.

The neutral switch basically just tells the ECU when the car is in neutral or not. It is mainly used with automatics to adjust timing/idle control since going from gear to neutral alters the engine load. On manual trans cars it may still be used, but it's affects are almost not noticed. As long as the AT/MT identifier pin is correctly identifying the transmission type (again assuming your using a MT), you'll probably be ok leaving it off if your transmission does not have a neutral switch.

Some people have wired the neutral switch up to the clutch switch, so the ECU will be told the car is in neutral when the clutch is depressed.

I've done both tranny & engine swaps on the first gen legacies, and have thoroughly researched the wiring issues, so let me know if you have any specific questions.

Josh

#5 Numbchux

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Posted 06 December 2006 - 04:29 PM

The 90-91 non-turbo engines have 3 square connectors behind the battery.
The 92-94 non-turbo engines have 2 square connectors behind the battery.
The 91-94 turbo engines have 2 square connectors and 1 round connector behind the battery.


Unfortunately. I don't think there's any pattern to it. as this case proves 2 of those statements wrong.

'93 EJ22t donor had 3 square connectors
'91 N/A legacy has 2 connectors.


I don't have my VSS hooked up. it runs fine. I've got some cold starting problems, but I have no reason to think its related. However, your car should have a VSS (refferred to as a Reed Switch on the diagrams) in the dash.

I have the neutral start switch wired so it'll always start. I've had to use the starter to move the car a few times....


and yes, a comprehensive write up is not far away...But there's a ton of information out there, so pulling it all together is taking time....But it will be soon.

#6 WoodsWagon

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Posted 06 December 2006 - 07:22 PM

I'm pretty sure the carb cars had a reed switch in the spedo, even if they didn't use it. The car can get real pissy without it. Bogging when you floor it, having to tease the engine up to speed when you're accelreating, that kind of annoying BS. Not having a neutral switch can make it stall. The clutch switch is actually used by the ECU. I have a jumper stuffed in mine, and it throws a code for the switch circuit. I wonder if it uses it for adjusting spark on startup?

#7 Legacy777

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Posted 06 December 2006 - 10:34 PM

Ok,

I looked in my parts books, here's what I found....even though it still sounds like it conflicts with what you've seen.

It does say that the 90-91 n/a's have 3 square connectors, while the 92-94 n/a's have 2 square connectors. It's possible there were a few that changed over early, maybe late 91 MY production vehicles....who knows.

Again the parts book says the 91 turbo used 3 square connectors, while the 92-94's used 2 square & 1 round connectors.

The ej22t in my car is a 93 MY, and it had 2 square connectors & 1 round one.

So it still may be a crap shoot.

The only other thing that is mentioned is that there were different engine harnesses for vehicles bound for Canada, the USA (49 states), and California spec vehicles. So maybe that too has something to do with it...

Josh

#8 Numbchux

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Posted 06 December 2006 - 10:49 PM

OK, I'm over here working on it again...I had it backwards. his donor EJ22t is from a '91, and the car it's going into is a '93....

so that makes more sense.

#9 Legacy777

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Posted 07 December 2006 - 12:27 PM

Ok....that's good to know subaru didn't just do things too willy-nilly :)

#10 Gloyale

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Posted 28 December 2006 - 05:45 PM

I'm pretty sure the carb cars had a reed switch in the spedo, even if they didn't use it. The car can get real pissy without it. Bogging when you floor it, having to tease the engine up to speed when you're accelreating, that kind of annoying BS. Not having a neutral switch can make it stall. The clutch switch is actually used by the ECU. I have a jumper stuffed in mine, and it throws a code for the switch circuit. I wonder if it uses it for adjusting spark on startup?


Uhh, I'm pretty sure the Carbed cars Did not have reed switches but it is a cinch to get one from a spfi or mpfi car. Anything fuel injected. You can swap the whole cluster. The exception to this would be 2wd carbed cars and california carbed cars which use the "feedback" carb. They also have the reed switch and those would work too.

#11 TomRhere

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Posted 31 December 2006 - 01:34 PM

The exception to this would be 2wd carbed cars and california carbed cars which use the "feedback" carb. They also have the reed switch and those would work too.


Would this also hold true for an '82 BRAT that was originaly a feed-back carb model?

#12 mikeshoup

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Posted 31 December 2006 - 02:35 PM

This was posted sometime before, but starting after a certain year, all Subarus have a speed sensor. I wanna say its either 82 or 83. Whether or not its feedback, whether or not it has cruise control.

My 82 FSM shows a speed sensor in GL and GLF models, and not in STD or DL models. Its a two pronged connector behind the dash and above the speedometer.

#13 TomRhere

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Posted 01 January 2007 - 04:17 AM

This was posted sometime before, but starting after a certain year, all Subarus have a speed sensor. I wanna say its either 82 or 83. Whether or not its feedback, whether or not it has cruise control.

My 82 FSM shows a speed sensor in GL and GLF models, and not in STD or DL models. Its a two pronged connector behind the dash and above the speedometer.


Thanks for the info......




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