Always wondered this...when you engage the cruise control, does it know what speed it's on (i.e. 70, 72, 56, whatever) or does it just hold whatever value the sensors on the vehicle put out?

I'm fairly certain that, on my truck, the cruise is tied into the PSOM (programmable speedometer/odometer module) circuit, and thus DOES know the actual speed of the vehicle.

I'll see if I can't find the electrical circuits to prove it.

Proof is in the pudding.

That isn't pudding you're stepping in there....

So all it really knows is the AC signal from the VSS, which could in theory be controlled? By that I mean you could feed the VSS sensor a 10mph signal when you were at 70 and engage the cruise control and it would hold 70 because as far as it knows it's keeping 10 mph, correct?

Will it only keep solid numbers such as 55, 56, 57 or if you set it in between 55 and 56 will it keep in between?

I don't believe that the VSS is feeding the PSOM & speed control with actual integer values for speeds. It should be feeding it voltages which the PSOM uses in conjunction with a math equation to display the speed in integer values of MPH on your speedo.

I'm just speculating but that seems logical--- since all the sensors either feed signals of voltage, current, or resistance to the computer in order to provide readings.

Assuming this is correct--- I think the accuracy of the speed control & speedo would be limited to exactly how accurate of a voltage signal the VSS can send to the components. A wild guess tells me its something like 2-3 decimal places.

Thanks for all the help Chris, it's been very informative.