Can VSS (circuit) be bad, but speedo still work?

I'm having a stalling/coast down problem with my 96Z, and it is setting a VSS code (P0500), but the speedo still works.

When I start the car sometimes I can't shift it to reverse without manually over-riding the lockout solenoid, and the cooling fans come on. Then a few key cycles later I can put it in reverse with no troubles and the fans come on when they are supposed to.

My main trouble is with the IAC and idle. It won't idle very well, and it dies when coming to a stop. I have 2 PCM's, one has a tune from Ed Wright that I got back in 2001 and it even has the problem but never did before I got another PCM and started using LT1 Edit.

Anybody have any thoughts? Thanks!

Anybody?

yes, read this.
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http://www2.sendthisfile.com/d.jsp?t=y4Xv37TjNdm9Kadw9kPzNa6w

yes, read this.
what's up with posting attachments?


http://www2.sendthisfile.com/d.jsp?t=y4Xv37TjNdm9Kadw9kPzNa6w

Thanks, but I have the service manual and I'm still somewhat in the dark. When using that flow chart, step 2 I get a speed reading when using a Tech 2. Where it says go to Diagnostic Aids it just says to replace the PCM. I don't understand how the PCM can be bad when the speedo and everything works right??