Looking at the wiring diagram I see that the Radio Fuse supplies power to the VSS on circuit # 43 through a yellow .5 mm wire.
I'm not sure if this could cause your problem but it shows there is a link between the radio and the vss. However the troubleshooting section does not mention checking the Radio fuse for vss problems.
Take a look at the Radio Fuse. Its cheap and easy to get to.
The Radio fuse is 10 amp and is located in the center of the fuse box about 1/3 the way from the bottom.
Hope this helps,
Carroll