Buick regal OEM cruise problem

I have to admit I am stumped. If someone can help me solve this, that would be just great - to say the least. Buick regal 99 cruise does not work. tested all connections at the cruise module. The only connection that acts funny is the VSS. The VSS sensor on this car goes into the PCM and the PCM delivers a new signal to both the cruise and the Instrument cluster. With an identical system (on a 96 Lumina) this wire climbed to 10.8 vac while on the bad cruise it never got past 4.8vac. We have a)changed the cars computer b)changed the Vehicle speed sensor c)changed the cruise module Now the dealer who sold the car wants us to put in a brand new cruise system. I would like to repair this one. Please help. Thank you

Check all the brakelights. If one's out it could stop the cruise from working. Have you tried a new switch??

The brake inputs into the cruise module are working fine

Check to make sure the bulbs themselves are good. Alot of cruises need to see a ground through the filament of the brakelight. If one's burned out...no cruise. Just a possibility. If your speedometer is working correctly then the vss is probably good. To test it you need to set your meter for Ohms and roll the car about 10 feet. The wire should pulse ground when rolling. Im just taking for granted that you checked the fuse to the cruise control

According to the schematic for this car, the ground to the cruise module is just a regular ground, but I will deffinitely double check. The speedometer seems to be working fine. I'm beginning to wonder if we should replace the actual wires between the vss, car's computer and the cruise. Perhaps there is a signal but not strong enough for the cruise.