You may have a bit of an issue with your planned set up. The reason I say that is the cruise is operated by varying the voltage on the Cruise Control Switch Signal in the BCM.
Basically the cruise is set by the "On" button on the wheel and it sends a 5 volt reference to the BCM to tell it to turn on. So this will work by using a simple toggle switch.
The "Set" "+" "-" buttons are all operated off of resistance. This means the BCM sees a varying voltage and depending on the voltage it knows what -speed to set the cruise control at. As you press the "+" or "-" it increases and decreases the resistance which changes the voltage that the BCM sees which tells it to increase or decrease the speed.
Does that make sense? Check out the diagrams (Below). Please let us know what happens. Let me know what questions you have. Thanks
Images (Click to enlarge)
Tuesday, June 9th, 2020 AT 10:10 AM