I have a 1997 ford expedition eddie bauer. The speedo is not working and it sent it into limp mode. I had it at the shop for about a week. They called and said come get this thing I cant figure it out. This is what my issue is. I started checking everything and found that the wire that is supposed to carry power to the vss is acting as a ground. Also 7 of the fuses in the fuse box in the cab are grounded but not blown. I unpluged the pcm and checked them again. Still grounded. Unpluged the g.E.M. And still grounded. What could cause this?