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91 ss power mode

Posted: Thu Apr 20, 2017 3:55 am
by 208ss
So im wanting to do the power mode mod on my 1991 legacy ss. But i have read that I cant because the pin 4 goes to the cruse control. I'm wanting to know if i get a tcu from a 92-94 na legacy would my connectors fit into it? or would i need to get the whole wiring harness from said car to make it work.
or If some one has made the power mode mod to work on a 91 tcu please chime in/

Re: 91 ss power mode

Posted: Thu Apr 20, 2017 5:49 pm
by Legacy777
From looking at the wiring diagrams it looks like that pin 4 to the cruise control is different and there's a pin B46 pin 15 that is on the 90-91 cars related to the speed sensor 2 and it's not there on the 92 wiring diagrams. In theory I think you could run the 92 TCU, however I'm not sure if the transmission would like the non-turbo TCU. You'd need to snip that wire at pin 4 so it doesn't interfere with the cruise (your cruise control may not work), and you'd probably want to look into whether your car has the pin for the speed sensor 2.

Re: 91 ss power mode

Posted: Sun Apr 23, 2017 11:42 pm
by 208ss
Do you have the different diagrams for the 91 and 92-94 tcm that you could share?

Re: 91 ss power mode

Posted: Mon Apr 24, 2017 5:50 pm
by Legacy777
These are from the 90 MY, but should be applicable to the 91. I'd have to double check when I get home.

https://main.experiencetherave.com/suba ... _page1.jpg
https://main.experiencetherave.com/suba ... _page2.jpg


Similarly I'll have to check the 92-94 when I get home.

Re: 91 ss power mode

Posted: Tue Apr 25, 2017 3:32 am
by Legacy777
The 90 & 91 TCU I/O is identical.

The only differences I saw was the 92-94 TCU I/O notes the atmospheric pressure sensor input is for non-turbo only.

The other thing I found was that the 90-91 TCU I/O has the brake switch labeled incorrectly. The 92-94 TCU I/O is correct and that's how the 90-91 is wired as well....the FSM is just wrong. You can check the individual wiring diagrams and they match vs. what the I/O lists.

So just use this scan

https://main.experiencetherave.com/suba ... CU_I-O.pdf