hey I swapped my 2.8mpfi out for a carbed 350, no computer now, now i am trying to get my speedo to work. I went out to the JY and found the electronic gear and wired the purple and yellow wire into the existing purple and yellow wire that comes out of the bulkhead on the drivers side. speedo still dont work, is that because the old speedo worked thru the computer? i dont know, but I want to get my speedo working

 

You didn't specify model and year of the car. Can I assume it's an '89 'bird?

An '89 Firebird did use an electronic spedoometer pickup (VSS) and it was routed through the ECM. So you're right. No ECM = no speedometer. And I bet your cruise control doesn't work anymore.

You can leave the computer in just for that but if you don't, you will need a way to get the VSS signal traslated for the speedometer (and cruise control). I think I have a thing just for that, I'll have to look.

Lou

 

Should be possible to just go mechanical. you'd have to get new guages though. I had to do that with my 91.

 

hmm..yeah i didnt have cruise control anyways. but dang thats a bummer, i guess I will just end up buying aftermarket guages cause I am having the hardest time finding a mechanical set out of an 89

 

Doesn't have to be from an 89. any mechanical set from an 85 on should do.

 

I actually have an instrument cluster from an '85 Camaro if that would work in a Firebird dash.

But if you don't want to swap all gauges, you can just use a small device to convert the signal from the VSS for the speedometer (what the ECM used to do).

Maybe (just maybe) the signal could be adapted by a single diode connected with the anode to the speedometer and the cathode to the yellow wire of the VSS to let the grounding pulses through but block the 12V pulses from the VSS. Anybody got any input on this? Would it work?

Lou

 

I don't know anyone whos tried that.

 

Looking at the diagrams I have for an 89 firebird with a 2.8L. You should have a VSS buffer. It is a small yellow or white box near the E.C.M. or where it used to be. Mike

 

Electronic? Dakota Digital offers a product that you might be interested in checking into...

http://www.dakotadigital.com/index.c...rod/prd126.htm

Product is the Universal Speedometer Signal Interface #SGI-5

 

hi 83z28camaro
I am swaping my Firebird (trans am) 1987 engine (4bbl) and trans. And I have a question about your yellow box on the ECU.
I am going to use a holley computer and a TCI controller for my 4L60 trans. But now the problems start.

I need a vss signal for both speedometer and TCI computer. unfortunaly the TCI box don't have and vss output I can use for speedometer!
Now I have just cut out the factory ECM and did find that yellow box, and I did think this is a splitter for VSS signal. Cause the VSS signal is not strong enough to drive both speedo and TCI computer!
Is this true...? If it is, then it can be used to suply my TCI box and speedo!

Is there anyone that know about this? If so there is 4 wires on one conector and 2 on the other, do someone know what is the input and what is the output?
Do this yellow box do any dividing or have any known feauture?

Thanks for all help!
Ingar


Hi have to inform you all that I have found tis out.
The box transform the signals from "sinus" into square pulses. Two of the output give 2000 pulses each mile and other two output give 4000 pulses each mile. then there is power to this box.
I have conection diagram awalibe if someone need that.
Ingar