Ok so I have a 1988 Trans am with a 350ci and 700r4. I did a carb conversion and now my speedo doesnt work. I haven't confirmed that I did not accidentally cut the wire to the VSS. I am just making sure that this might be an issue with removing the ECU and wiring to the computer.

Any thoughts?

 

on mine my cable goes straight from the tran to the back of the dash.
Is yours electric/digital? (sorry, I dont know much about trans am's.)

If it worked before, you need to back track and find out what you did.

Hang tight and someone will help ya.

Like sofakingdom says, The simplest explanation that fits all the facts is probably the right one.

 

no cable on mine its electronic

 

There's a smaller yellow or white box next to the computer called a vss buffer box. I'm gonna guess you prolly removed it with the computer. The signal from the vss on the trans runs to the buffer box that converts it to a use able signal for the speedo read and display.

Signal goes from the sensor to the box then the box splits it into use able signal for the speedo, cruise control, and ECM. All of which use a different signal. It's basically a diverter box.

 

well crap..... is there another way to make it work? I got rid of all the stuff. I no longer have it

 

also will it work if I was to get it back and plug it in without the ECU?

 

You'd either need to get an aftermarket speed that can use direct vss signal or put the box back in. No you do not need the ecu, just the vss on trans, wiring to the box from the sensor and the one wire to the speedo.

 

Cool so plugging the box back in using existing dash harness should do the trick then?

 

As far as I can remember yes

 

ok so I got the VSS box back and installed it. The speedo is still not working. Any thoughts?

 

What did you do when you swapped? Cut anything?

 

I just unplugged the ECU and removed the harness for the ECU to engine. I don't believe I cut any other wires or anything.

 

The wires to the vss sensor are part of the engine harness. It then connects to.the dash harness via the square connector.

Youve got wiring to do...

 

Ok I will go over schematics and see if I can track down how I need to fix it.