wiring help

[Denvernic]

I got an 87 K5 there is a yellow wire with a single connector on it that is coming from the cruise control module box its a lil black box under the dash. Does anyone know where that wire goes?

 

[chengny]

Speed sensor on the transmission?

 

[RetroC10Sport]

But 1987 would have a cable speedo and the sensor/buffer would be on the back of the speedo. In which case, it does go to the back of the speedo.