Me again. While I am searching for a replacement auto. trans. and hoping for th weather to "warm up" a bit so I can throw it in, I was wondering about the electronics accociated wih this system. I understand there is a microprocessor based Transmission Control Unit (TCU) somewhere in the vehicle and of couse I am only too aware of the Engine Control Module (ECM), although my dealings with the ECM have been only on my OBD-II equipped '97 Legacy. The only manual I have for the '92 is a Haynes and it does not address the TCU (nowhere does it even mention "TCU").

 

Anyway, the current questions are:

 

1. Is there a way to interrogate the TCU to see if anything is bothering it?

 

2. Can I get any transmission related information from the ECM/OBD-I?

 

Thanks again!

 

 

Mike V.

Hi Mike, Here is some reading you might

be able to use.

4EAT diag

 

Search the "Archives" for more on the 4EAT.

 

Hope this helps.

The TCU is right next to the ECU. This pic shows both

 

http://www.main.experiencetherave.com:8080/subaru/images/ecuhide.jpg

 

I also have how to pull codes from the TCU on my site

www.surrealmirage.com/subaru/trans.html

Thank you VERY much triple seven. I have read (or alt least scanned) through the end wrench articles and I have looked at lots of A/T threads in the archives and I have researched ny Haynes manual and NOWHERE else did I find the instructions you provided as to how to extract data from the TCU!

 

From looking at your photo, I am tempted to conclude that the ECU on the 1992 Legacy is not below the glove box as it is on my 1997 Legacy. Correct? Perhaps the ECU and the TCU are located on the driver's side under-dash on the 1992?

 

Another question/comment: The instructions you posted for reading the TCU codes refer to the "Power Lamp". I noticed that some end wrench articles referred to the Power Lamp while otheres referred to the AT Oil Temp lamp. Did they change the nomenlature at some point? I apologize for not knowing what the lamp is called on my 1992 but I do not drive the car. In fact, I don't normally drive either of the Subarus that I maintain. But I do drive by boxer power (VW).

 

Thanks again!

 

Mike Vanderzanden

The later subarus (I think when they went to OBDII) don't have the power light, so the AT Oil Temp light flashes to indicate there is a problem.

Thank you VERY much triple seven. I have read (or alt least scanned) through the end wrench articles and I have looked at lots of A/T threads in the archives and I have researched ny Haynes manual and NOWHERE else did I find the instructions you provided as to how to extract data from the TCU!

 

You're very welcome

 

From looking at your photo, I am tempted to conclude that the ECU on the 1992 Legacy is not below the glove box as it is on my 1997 Legacy. Correct? Perhaps the ECU and the TCU are located on the driver's side under-dash on the 1992?

 

Yes the ECU & TCU are located under the dash on the driver's side on the 90-94 legacies. In 95, when they went to OBD2, the ECU got relocated to under the footwell on the passenger side.

 

Another question/comment: The instructions you posted for reading the TCU codes refer to the "Power Lamp". I noticed that some end wrench articles referred to the Power Lamp while otheres referred to the AT Oil Temp lamp. Did they change the nomenlature at some point? I apologize for not knowing what the lamp is called on my 1992 but I do not drive the car. In fact, I don't normally drive either of the Subarus that I maintain. But I do drive by boxer power (VW).

 

Thanks again!

 

Mike Vanderzanden

 

As snowman pointed out, the later models, when they went to OBD2 use the AT Oil temp light instead of the power light.