Voodoo121

Hi all
I built a hot rod and used a 1990 IROC Z TPI motor and trans, and complete wiring harness as i am not a real wiring genius. So far all went well, with the exception of trying to wire in a aftermarket guage set. Everything was easy with the exception of the speedo. The dolhin only needs a single connection to the speed sensor. I am not sure what that would be. I am assuming the two purple and yellow VSS wires need to input the ECM 16198262. So i am assuming that the speedo input would be from an output of the ECM.

Does anyone know what i hook the programable speedo up to? Output of the ECM 16198262?

Should admit that when i pulled the harness from the car, there was a small sub yellow taped wire section that i "assumed" was for the air bag. I cut it out and threw it away. Hope that was not a boner move...

Thanks All
John

Voodoo121

Here is the simple wiring diagram that comes with the speedo set. The instructions are clear. Just need to know what to hook the green wire to....

Jonesyfxr

iTrader: (2)

Ask Tuned Performance, I'm sure he'd know.

RBob

iTrader: (1)

From the ECM, pin B11 is a 4K PPM digital pulse stream. If the speedometer can use that type of signal, it is all that is required. Leave the yellow & purple VSS wires alone, they still go to the ECM.

RBob.

Voodoo121

RBob
Thanks for the quick help! I located the B11 pin and chased it through the first connector where the wire changed to Grey. That wire went to where the old IROC cluster was and i attahed it to the Dolphin speedometer guage. In idle the guage read like a tach and rolled up a with throttle like a tach. In gear, i went to about 50MPH, but the guage did not seem to be responding to the VSS signal to the ECM, but still like a tach. I am pretty happy that i am made progress, just not quite all the way there yet. I will contact Dolphin to see if there is a guage compatibility or programming thing i need to do. Unless some one knows the answer to this question as well. That would be awesome. Thanks again, one step closer!!
John

Voodoo121

Jonesyfxr
Thanks for the tip, i have seen some of his stuff. Impressive. RBob gave me a path and i am running it down now. Cant wait to solve it. i have spent a week by myself with no luck....better now with help...

Voodoo121

Update!!
Step 1 - found wired the speedo input wire to the ECM 4 k output - No joy, guage was reading like a sluggish tachometer. Neutral or on the road read the same.

Step 2 - wired the speedo input wire to the VSS yellow wire (yellow still input to ECM) - No joy, guage was reading like a sluggish tachometer. Neutral or on the road read the same.

Step 3 - wired the speedo input wire to the VSS purple wire (purple still input to ECM) - No joy, guage was reading like a sluggish tachometer. Neutral or on the road read the same.

Step 4 - Disconnected the VSS connector, wired the speedo input wire to the VSS direct, other VSS terminal to ground. - joy, Speedo works like it should!

Question: By disconnecting the VSS from the ECM, what have i messed up? Will the trans now shift funny or did i mess up some sort of ECM fuel mapping that needs the VSS signal to work?

Any expertise would be great. The Haynes manuals really dont explain the theory at all.

Thanks in advance!

John

Voodoo121

Another quick question: Does my 1990 IROC Z suppost have this VSS Buffer Module? I thought my VSS wired directly to the ECM. This pic suggests i am supposed to have a VSS. Hmmmmm

RBob

iTrader: (1)

That buffer is built into the '90 - '92 TPI & MPFI ECM.

As far as the ECM not having a VSS input, that will affect a bunch of items. The TCC lockup will be the most noticeable loss.

RBob.

gw082008

Hopefully you can see this and disregard the "pencil scratchings' - my PDF version would not load on this site.
This is pin out from the ECM for the VSS sensor, speedometer, and cruise control.

Voodoo121

Thanks gw082008! Wiring diagrams are the best for me to read (good ones that is).
Its all starting to make sense, now to make it work.... Looks like from yours and RBobs reply, that i do need the VSS input into ECM. I am looking to see if there is either a duel output VSS (one for ECM and one for te speedo) or some way to condition the VSS ECM 4 PPM or 2 PPM output to what the speedo can work with.
Thanks again, i will keep you all posted
John

Voodoo121

Thanks RBob. I am convinced to keep it connected. Looking for some wat to condition either the 2 PPM or 4 PPM ECM output to my speedo.
the hunt continues...

RBob

iTrader: (1)

This is the issue, Dolphin doesn't specify what signal their speedometer requires. If I was using one I'd bug them until they gave up the spec, then the proper signal can be provided.

RBob.