[This message has been edited by Darth Fiero (edited 03-31-2008).]

Here is a wiring diagram from a 1988 Fiero that shows the proposed electo-power steering VSS wire. This wire might be a 4000ppm signal that can be used with the "digital" cruise control...

FieroVSS.pdf

If that doesn't work, and you don't want to buy the aftermarket SGI-5 interface, you should be able to use a factory GM speedo buffer box from a 80's GM car. These boxes look like this:



The wiring diagrams for this buffer box can be downloaded here: http://www.gmtuners.com/files/4-OUT_BUFFER.pdf

This yellow "4-out" buffer box was used in many mid-late 80's GM cars such as the Pontiac Firebird, Pontiac Grand Am, Chevy Cavalier, etc; and can usually be found piggy-backing the ECM.

But before getting one of these buffer boxes I encourage someone to try hooking up to that "M" terminal coming off the stock Fiero speedometer to see if that works.

-ryan

[This message has been edited by Darth Fiero (edited 05-16-2008).]

quote Originally posted by Darth Fiero: Here is a wiring diagram from a 1988 Fiero that shows the proposed electo-power steering VSS wire. This wire might be a 4000ppm signal that can be used with the "digital" cruise control... If that doesn't work, and you don't want to buy the aftermarket SGI-5 interface, you should be able to use a factory GM speedo buffer box from a 80's GM car. These boxes look like this: The wiring diagrams for this buffer box can be downloaded here: VSSbufferWIRING.jpg This yellow "4-out" buffer box was used in many mid-late 80's GM cars such as the Pontiac Firebird, Pontiac Grand Am, Chevy Cavalier, etc; and can usually be found piggy-backing the ECM. But before getting one of these buffer boxes I encourage someone to try hooking up to that "M" terminal coming off the stock Fiero speedometer to see if that works. -ryan

It does not look like there any wires going to those three terminals by the only photo I have now.



The pins we are using now are P R S T U and the 3 before that are nothing.

Ed
EDIT: One of those four holes is the 4K signal and if you have an oscilloscope or just a COMPUTER SAFE test light the wire could be found by testing each wire while you turn the wheels, the one that blinks on and off will be the 4K signal. I don't think this is the best way you still have to get the wire out to the engine compartment.
The speed buffer box could be used in the engine compartment and get all connections needed there.

[This message has been edited by Fino (edited 03-31-2008).]

Here is another photo of the other side.



Ed

EDIT:
The first photo is an 85 MPH speedo and the second is a 120 MPH speedo. Look at the extra circuit on the 120 MPH that is not scratched it does not go up to the 4 holes but I wonder what it is. You might think a ground but that screw goes into plastic.
??????????

[This message has been edited by Fino (edited 03-31-2008).]

Remember, GM usually skips letters like "I" and "O" in their wiring terminal ID's so they aren't confused with the numbers "0" and "1". Looks like terminal M is hooked up to the circuit board and isn't used in a stock Fiero application minus pwr steering (it lacks the marks you can see made on other terminals by connector being plugged in).

[This message has been edited by Darth Fiero (edited 03-31-2008).]

Might be



My car does not have a computer in it now or I would test it to see if the test light to ground flashes. This would be very easy for anyone to do by using a computer safe testlight and probe the terminal. It is very easy to get to.

Ed
EDIT:
Note that "P" and "R" connect together. That would be low VSS and Ground.

[This message has been edited by Fino (edited 03-31-2008).]

quote Originally posted by Darth Fiero: Bet it is. Looking closer at the wiring diagrams for the stock Fiero speedo, you can see the 2000ppm VSS output from the speedo circuit board hooks up a to "divided by 2" logic circuit. The output terminal for the power steering module hooks up to the "divided by 1" logic circuit, which would stand to reason this is a 4000ppm output. I think it's worth a try. -ryan

Ed

EDIT: Remember the speedo has to be a 120 MPH speedo the 85 does not have it. Now on later cars will it be there? I don't know what year my 85 MPH speedo was.

[This message has been edited by Fino (edited 03-31-2008).]

This is a pic from Jon. I think terminal M was active on the '88 models and terminal N was active on some of the earlier years. In this pic, looks like M isn't connected to anything but N is.

I was gonna test these terminals tonight, but i have 3 buffer boards and NONE of them have any circuits connected to K, L, M or N .

[This message has been edited by PaulJK (edited 04-01-2008).]