GM Repair Questions? Ask a Mechanic for Answers ASAP
If the green wire between the VCM/PCM is shorted to ground or power, the speed signal would not be received by the IPC. I'll send you the schematic. There's not much else it could be if the VCM is seeing the signal. Either the wire is damaged between the VCM and the IPC or the VCM is defective. There are a lot of problems with corrosion on those VCM's.
Here's the schematic.