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boostjunkie was telling me that he had had difficulty finding the correct ECU pin specifications for his car, so I put this together. I've done a bit of research on Legacy Turbo ECUs and combined the info from Subaru and from examining actual cars and came up with this:

http://www.graphics.cornell.edu/~v/ecupins/

I hope it helps anyone doing any kind of ECU wiring.

(edit: changed title to include EJ22)

Kick ass. Now, Id like to have the same for non turbo please

(I dont mind to help)

Ciper, I can email you the versions for the 1990 N/A legacies that used to be on Josh's page. Not sure if he still has them on there (said he had problems with hackers a while back).

Thanks again, vrg3!!

The non-turbo pinouts changed a little over the years, and I haven't examined NA cars as closely, but I'll see what I can come up with.

Which year(s) in particular are you most interested in, ciper?

All of them. I have the FSM, but it would be nice to have something in the same format as yours, so it would be easy to compare the two.

Scans from the 1990 legacy FSM

http://www.main.experiencetherave.com:8 ... _page1.jpg
http://www.main.experiencetherave.com:8 ... _page2.jpg
http://www.main.experiencetherave.com:8 ... _page3.jpg

future reference....all my FSM scans can be found here
http://www.main.experiencetherave.com:8 ... ual_scans/

I took a look at the wiring guides and charts (both from Subaru and from third parties) for some NA models and looked at the pieces of wiring harness that I have from NA Legacies and it appears that the NA ECU connectors are the same except:

- The cam and crank angle sensors are switched
- The wastegate control solenoid, pressure exchange solenoid, and MAP sensor lines are missing (of course)
- Up until 1992 there was an atmospheric pressure sensor signal (1993 and later ECUs had the sensor completely internal)

I've updated the web page so now it should correctly cover both turbos and non-turbos.

" Up until 1992 there was an atmospheric pressure sensor signal (1993 and later ECUs had the sensor completely internal) "


Explain this one. You mean the turbos have this sensor right? I know the NA for 90-91 at least have the atmospheric sensor inside the ECU.

The turbos have the sensor listed as the "MAP sensor."

From what I understand, the naturally aspirated ECUs all contained the barometric pressure sensor, but until 1992 the signal was brought out on B48 pin 16 (for the TCU or something). 1993 and 1994 ECUs had nothing connected to this pin.

Someone please correct me if I have this wrong.

It's possible the TCU now had it's own barometric sensor.

That line does go to the TCU and does make a difference.

One thing I did notice when looking at select monitor info is that the TCU values were always off slightly from what the ECU read. TPS readings, atmospheric pressure, etc. It's weird. I was told by a subaru tech that this was normal.....

The ECU supplies a 5 volt reference that is either used by sensors or used to interpret sensors. That reference can be off by up to a couple tenths of a volt. As far as I know, the TCU never gets to see the actual reference voltage from the ECU, so it has to have its own internal reference. I'm sure that reference can be off by a couple tenths of a volt too, so it's not that weird that they should read slightly different values.

I see........so could you tie the reference voltages together, or would that just be bad?

and which pin does the reference voltage come out........

No, you shouldn't tie them together, since both units are trying to drive the voltages.

I don't know much about TCU wiring, but as far as the ECU, the TPS power supply and MAP sensor power supply (on turbos) carry the 5 volt reference. I'm not positive about this one, but I do believe that MAF sensor pin 5 carries the reference as well (I guess this allows the aluminum-body sensor, which uses this pin, to be used more precisely or something).

I also believe that several other pins are digital inputs with pull-up resistors to this reference, including the VSS, test mode and read memory connectors, transmission and jurisdiction ID, and neutral and park switches. So if you disconnected whatever's hooked to any of those and measured the voltage you'd see the reference voltage also.

Now, it's not clear where the play in reference causes different readings. The ADCs in the ECU could read either absolute voltages or voltages relative to the reference; I don't know. The sensors could also output absolute voltages or relative voltages. For example, I know the TPS signal is relative to the reference, but I know the plastic body MAF sensor outputs an voltage independent of the ECU's reference (since it has its own internal reference).

is the ecu in the auto any different than the one in a 5spd?

suberboy wrote:is the ecu in the auto any different than the one in a 5spd?

nope

suberboy wrote:is the ecu in the auto any different than the one in a 5spd?

Well, the ECU part number for 4EAT cars is different from the part number for 5MT cars, with two exceptions. All turbos from 91 to 94 had the same ECU part number, and all non-turbos in 1992 had the same ECU part number.

The transmission ID pin is how the ECU knows what kind of car it's in. It's grounded on automatics and left floating on manuals.

So it's weird... It's not clear what the difference (if any) is between a 1990 automatic ECU and a 1990 manual ECU, and the ECU does have an input that tells it the type of transmission, but the part numbers are different.

For what it's worth, this is the part number info I have:

1990-1991 4EAT NA: 22611AA38x
1990-1991 5MT NA: 22611AA56x
1992 NA: 22611AA93x
1993 4EAT NA: 22611AB05x
1993 5MT NA: 22611AB06x
1994 4EAT NA: 22611AB76x
1994 5MT NA: 22611AB77x
1991-1994 Turbo: 22611AA69x

Where the x is the part revision number.

When the ECU is running in "automatic" transmisison mode it will adjust timing at idle, where in manual mode timing is static at idle.

i've read that the ecu will provide the year of the ECU, but you need the select monitor tool to get that info.

Yes, the Select Monitor can ask the ECU for its ROM ID, which is three bytes long.

ciper wrote:When the ECU is running in "automatic" transmisison mode it will adjust timing at idle, where in manual mode timing is static at idle.

I was just playing with the Select Monitor and noticed that when I'm out of gear, in neutral, the ECU does indeed keep timing static. But, when I'm in gear (even if declutched), the ECU dynamically varies timing. Maybe it does this to try to maintain idle speed even when the engine is loaded (since it doesn't know about the clutch)? That would make sense, since an automatic is never fully unloaded since it has to spin the torque converter.