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 and CONVERT THAT to revolutions per mile, 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 (25.65" --> 820 RPM) + 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.

 

Gentlemen,

After further messing around this is where I am.
- Dakota Digital is back in, has power and the app reads MPH. Calibration is set to 1.30.
- ECM / TunerPro is still not receiving any reading besides -4mph.
- I tested OHMS on the Output wire to b6 and no issues there.
- I have checked and unchecked B6 on TunerproRt. No change either way with the flag. Currently checked.
- VSS PPM are set to 4000 on TunerProRT.

At a road block now. Hoping someone else can identify an issue I may be over looking. Thanks for the help.

 

This is what I wound up with:
IGNITION+ to +12v switched
GROUND- to ground
SPD+ not used
INPUT to yellow from TKX VSS
SPD- to purple from TKX VSS and purple to ECM B9
OUT1 not used
OUT2 not used
OUT3 to yellow ECM B10
OUT4 not used
OUT5 not used
SPd out to H-L and then set the "cal" to 1.55 (I have 3.23 gears). This got me within ~10%.

 

B6 ? Try c6 out 5
or as rt66 suggested

 

Yeah, B6 would be the MAP and coolant temp sensor ground (should be a black wire). Don't know about C6 (my factory manual shows that going nowhere). ECM B9 (purple) is vehicle speed sensor ground and B10 (yellow) is vehicle speed sensor input.

 

 

Weird. This is from my 1990 factory service manual...

 

In a 3rd gen optical Vss wasn’t used just magnetic pulse that’s why it’s not shown.

 

@Tuned Performance Yea, that was a typo my bad. I have it running to C6. I also did run it as magnetic, only when back to optical in the event I had misread something.

@rt66er Your previous responses in other posts is actually what I tried before this. If you scroll above my previous post, I had ran your setup without any luck. I wasn’t sure if the difference was because I was coming over from a 165 to 730 and another wire was missed? Since the buffer box was deleted in those years. Or if the T56 just ran different numbers then the TKX you had.

After Calibration with DD wouldn’t OUT5 not produce enough PPM? For the ECM?

 

what does it mean when it when it says "ppm values are only valid when calibration is complete"? Is that a process that you've already done?

Another option might be to ditch the Dakota box and put in a DRAC module. I had to run a DRAC module with the Gear Vendors VSS. At least then you're dealing with all factory hardware. Not sure if the one you already have is the right setting...

https://www.thirdgen.org/forums/diy-...ss-signal.html

 

Aha! Thanks.

 

I’m not sure the application used maybe cavalier

 

As far as I know, TKX and T56 VSS both produce same signal. My car was originally TBI 5.0 and auto; converted to TPI and 7730 ECM (re-pinned) so my wire colors aren't correct, but as I said, what I did works (including cruise control). My car originally had the yellow buffer box, but that was deleted with the 7730 conversion (this was done long before the TKX swap).

 

Thanks @rt66er I went with your setup. No buffer box, used the SGI to correct the signal. Again, the SGI is reading MPH but tunerpro isn’t capturing anything.

only thing not showing in my write drawings are the power and ground for the SGI. Which I’m assuming are just fine since I’m connecting on the app. I’m simply reusing the power and ground that the buffer box used to use.

calibration is set to: 1.30 which should send the signal of 4043PPM to the ECM input.

Also, I swapped around the purple and yellow in the event the t56 purple was the high and the yellow was low. I know that doesn’t matter but in case someone asks.

 

Dumb question, but what adx file are you running? And what are the settings in the vehicle speed gauge?

 

Not a dumb question, S_AUJP_7 is what I’m currently using. As for setting we have the VSS Reading set to 4043. And I’ve checked/unchecked the flag for Magnetic/Opt.

Is there a particular one you’re thinking of?

 

No I mean in the adx file... My guess is you haven't messed with the gauge in the adx file, but just to leave no stone unturned...

 

No actually, my old man that got me into these 3rd gen’s is a little more familiar with TunerPro and the ins and outs. I haven’t ever looked at the Adx Editor before.

 

maybe email it to me. Also if you get a datalog... send that too. I can replay it with my adx. Make sure its not a tunerpro issue

 

Dude I am so sorry, I forgot a pretty important step, just realized. PRETTY IMPORTANT to get an accurate PPM number: you take your tire height in inches, THEN CONVERT that to revolutions per mile. So with stock 245/50/16s, at 25.65" tall, you actually have 820 revolutions or so per mile...... VSS will be WAY off if you just use the tire height. I did my calculations correctly initially, but completely forgot that step when I was doing my TKX swap write-up.... just edited that, and wanted to come here to correct myself here as well. I'm going to edit my initial message in this thread to prevent any confusion for other folks in the future, apologies once again..... this wouldn't be causing your ECU to completely miss the signal though, so it wouldn't really matter for you if the ECU isn't getting a VSS signal at all. Your ECU would still get the signal, but it would be reading the speed WAY too high. Triple checked everything else in the calculations, thankfully that was the only error in what I said.

Just to get it all correct in one spot: Tire height in inches, converted to revolutions per mile (you can find conversion charts/ calculators online). For 245/50/16s, this comes out to approximately 820 revolutions. Multiply your tire RPM(ile) by your rear gear ratio, and multiply that again by 17 for the T56 VSS, and you have your actual correct PPM.

 

This is how we are set up now, this DOES work. We had a busted wire coming from VSS after tracking continuity through all our wires.

Buffer box is replaced with the SGI 100. The 730 ECM is setup as shown in this schematic. We fell within the range of 1.31 for calibration with the SGI100. Speedometer and ECM are lined up. Thanks again for all the help!