i'm pretty sure i've posted about this before, but i'm still having the issue and ive tried everything out there again and again... here's the details
i have a 92 RS. Originally a 305 tBi car with a 5speed.
a while back, silly me wanted to try some FI stuff. So i swapped in the tPi out of a 91z28 (supposed to be a 350 car). auto trans.
so i swapped the wiring harness from the tpi car.
i have 2 wires in the harness but 2 on the VSS in the t-5 transmission.
Since this photo i'm posting, ive run 2 wires from the trans up to the ecu, to color match with the corresponding wires of course.

so, speedo doesnt work.
question i guess is, how do i get to work? which wires should i tap into for the ECM or VSS (clear box) pinout????

any help is much appreciated!

 

On the '730 TPI ECM, the VSS signal goes direct to the ECM then the speedo signal is sent to the IP
Terminal B11
http://www.chevythunder.com/fuel%20i...ecm#1227730%29

On a TBI car, the VSS goes to the buffer box then to the ECM
https://www.thirdgen.org/forums/post...777-post7.html

so I suspect you would need to look at both circuit diagrams and see how to wire the ECM output back to the existing IP

TP will be along soon ; he is more knowledgeable about TBI's and buffers

 

Thanks :-) waitin for weather to clear up so i can do work

 

The tbi vss buffer output can be wired to c6 of the ecm and work with memcal reprograming. Just another thought

 

Yea except i wont need the ecm for anything else, ive gone back to carb and added some engine internals

 

If you need a tbi vss buffer and pigtail lmk

 

Problem is that each system uses a different VSS... The TBI more than likely uses a 2000 PPM VSS while the 730 system uses a 4000 PPM VSS.

Only way I found to make both the speedo head and ECM happy was to splice (either join the buffer wires to the ECM wires as they are or splice the ECM wires to the buffer wires, in parallel) the VSS buffer input wires (the yellow and purple ones) BACKWARDS to the ECM VSS input wires. Why backwards, I don't know, but it's the only way I got my speedo head to work and no code 24 from the 730. And this was after just hooking up the VSS as it's supposed to be hooked up to the 730 and using the 730's speedo drive to try to work the speedo head (which didn't work). Without the buffer, the speedo will NOT work unless the VSS is replaced.

This was before I learned that the 730 will accept a buffer input with reprogramming the MEMCAL. Not that that would have helped me since I don't have any way to burn chips...

And yes, I know you have already gone to carb, but this might prove useful to someone in the future.

 

Soooo right now i can try what you did (i won't get a CEL anyways)...or i can try finding a tbi ecm...
About right?

 

why dont you just wire it like this and hook up a,b a,c,h
if it needs calibration disregard the vss buffer and install a dakota digital agi-5