Been hassling with my 94 Regal Custom 3.8 cruise control for some time now. It just flat out quit working. The indicator light never comes on. Finally asked a reputable shop to diagnose. They said it was the control module. I put in a new module and there was no change. I checked most signals to the cc module - brake cut-off, multi-function lever and power/ground and all looked good. Finally took it the Buick dealer and they also said it was the module - I put in another new module - still no fix! Now what?? (The shops don't like to talk with 'competing' do-it-yourselfers :)
I have not been able to find any info on the signals from the main engine control module (3 wires) to the cc module. I think one of them is from the Vehicle Speed Sensor (VSS) but if that is bad it seems like other performance issues would be evident. Has anyone encountered this kind of problem with the VSS? (Anyone know where it is located on this car?) The wiring diagram (Chiltons) shows one other switch that is called Cruise Control Cut-Off - anyone know what/where that one is?
Another possible symptom is that I have a vague perception that the automatic door locks take longer to activate when starting to move. Also, the trunk lid release button will activate no matter what gear the car is in (supposed to work only in Park.) This makes me think a speed or gear position switch may be involved??

OK - I got a positive fix :)
The Reverse/Neutral Safety Switch mount on the transaxle was the problem. This affected four 'problems' - cc, door locks, backup lights and trunk release.
The cruise control module had been wrongly diagnosed because the scan of data from the main ECM indicated that the cc was enabled when it really was disabled - that could be a problem in the ECM but with no other symptoms becomes a non-problem now.

VSS? (Anyone know where it is located on this car?)

Did you ever find it? My Speedometer hasn't worked reliably for about 5 years...
Works when it wants to... Great thing is the odometer also takes a break.
Wonder what kind of gas mileage I'm getting though..

Haynes book says,
'The VSS is located in the transmission housing at the rear section near the output shaft.' ...
'..is located on left (drivers) side of extension housing'

Couldn't find in Chilton.