Hello, first post here and a thank you for all the help I've read in the past.
I have a non working speedo and have replaced the speedo head and vss with a working one to no avail.I've read where your supposed to have 5 volts on the sensor wire and blue is ground, I have 0 volts on the white/orange wire.
I've also read where your not to have any voltage and the sensor generates its own voltage? I can read the on/off the vss sends via a ohm meter at the post where ths speedo head plugs in the dash., and I have 12 volts on the middle post and ground on the top. any help would be great.
It's a 1991.5 , auto.

 

Is the VSS getting a good ground?

Are you sure the VSS is turning? Sometimes the drives get stripped out.

 

I was watching this repair as it is at my house. They ran another ground along with the blue wire and checked with ohm meter for ground. Yes the vss is turning, I could read the on/off's with ohm meter from behind speedo at the sensor post also this one is from my truck which works good.I took the parts from his that didnt work and put them on mine and they work ok! Does the pcm control the speedometer?

 

The PCM does not control the speedo.