Gentlemen, looking for your assistance.

Current setup is 89 Trans Am with a T56. Did the ECM swap from a 165 > 730 ECM and converted to Speed Density.

My last reading I need is my VSS. This is the current setup, and I’ve tried a few different. The APP has given me a reading but tunerpro and my speedo are not capturing any reading.

IGNITION+ to Pink/Black Power @ Buffer Box
GROUND- to Black/White @ Buffer Box
SPD+ not used
INPUT to yellow from VSS
SPD- to purple from VSS and purple from buffer box closed.
OUT1 not used
OUT2 not used
OUT3 to yellow buffer box
OUT4 not used
OUT5 not used
SPd out to H-L and then set the "cal" to 1.181 (I have 3.73 gears).

 

Here's a link to something that may help?

https://www.thirdgen.org/forums/tran...gital-sgi.html

It may be that you don't need that DRAC module in the mix... Post #14?

 

I appreciate that. I have been eyeing the setup in post #14. Only difference is his setup didn’t have the buffer box.

I am considering cutting out my buffer box and going directly to the ECM and see if I get anything.

 

GM got rid of the buffer box in 1990, so it could be that your setup with that buffer box is somehow causing an unknown issue.

 

I’m definitely leaning that way. I may have to see the schematics for without the buffer in the 90+ models. I figured at this point someone surely came across my same issue.

 

If you're running into a '7730 now, yeah, buffer box is probably causing some weirdness. '7730 cars (like the $88 3.1 and $8D TPIs) have the VSS running straight into the ECU. If you're running $8D, I BELIEVE you can just change the "Road Speed Constant" value in the BIN, so your ECU knows what pulse to expect from the T56 VSS. Should be 17 pulses per rotation on a T56 sensor. I just did this for my TKX swap, same sensor, though I did my parameter changes in $88 (for the V6). Anyways, you take your tire height in inches, multiply it by your rear gear ratio, and finally multiply that by 17. Plug that into your Road Speed Constant (or whatever they may call it in $8D, should be 4004 by default), and your ECU should be happy.

I believe you could forego the Dakota Digital box as well, if you're running $8D. If you see a parameter called "Instrument Panel VSS Pulse Divider", this is how you set the pulse that will be sent from your ECU to the speedometer. Basically, it'll divide your VSS pulse down to a pulse that your speedo can understand (it expects 4004 as well). I can't verify for $8D, but on $88 and $A1, they use hex values of sorts to do this:

divide by = decimal value

1 = 0
6 = 128
7 = 64
8 = 192
9 = 32
10 = 160
11 = 96

In my case, since my tires + 3.23 rear end gave me a VSS signal of 44,956.1 ppm, I entered 96 for the IP Pulse Divider to divide that by 11. Speedo reads within 2% of actual road speed, though you might be a little further off if you have numerically higher rear gears and/ or taller tires. The Dakota box can probably get your speedo closer, and you might as well use it since you already have it, but thought I'd throw that out there Just checked an $8D XDF, and found Road Speed Constant/ the Pule Divider are there, so you should be ready to rock if you change those parameters. Looks like you have an Autoprom or somethin hooked up, so should be pretty straightforward

 

I don’t get the use of 2 buffers essentially

 

Thanks for those responses. @Tuned Performance I was wondering if that’s what I was basically doing with the Dakota digital and the yellow buffer box. I was just battling in my head how the ECM was taking those readings.

@LLCooLM495 I think you’re spot on. I have the pin diagram and can run my VSS directly to the ECM. The output from my ECM would be:
Pin B11 > green/black to the Speedo (4000 PPM)
Pin C1 > Red that goes to cruise control (2000PPM)

From the yellow buffer box I would just be left with the Pink/Black power wire and the Black/white wire. I could just block those out.

Think that sounds right to both of your points.

 

Dropped the Yellow Buffer Box and DD. Wired right into the 730 as its setup for a regular 90s+ 3rd gen. Still no reading showing on Tuner Pro or the Speedo. Made some changes within the bin to reflect the reading the .bin is receiving too and nothing.

I have one more configuration using DD box again but I was looking forward to a direct plug into the ECM as they did when they produced the 730.

anything I may have missed?

 

Maybe post a schematic of how you have everything hooked up?

 

I hope this helps. Pretty straight forward. I removed the Dakota Digital Box and the Buffer Box. Removing the buffer box left me with 3 wires untouched. 1 - Pink/Black Power / 1 - Black/White / 1 - Brown that used to transfer VSS information to the ECM.

I identified the ECM Pin locations because when I did the ECM Swap those 4 were left untouched. A10 from the 165 ECM went to the C6 on the 730 ECM which is likely the brown.

 

https://www.thirdgen.org/forums/elec...sgi-100bt.html

c6 requires the optical flag change from
mag in the bin just for what it’s worth.