The stepper motor cruise control (SMCC) is a speed
control system that maintains a desired vehicle speed under normal driving
  conditions. Steep grades, up or down, may cause variations in the selected
  speeds. The cruise control system has the capability to perform the following
  functions:
The cruise control module contains the following components:
|     •  | An electronic controller | 
 
The controller performs the following functions:
|     •  | Monitors the vehicle speed | 
 
|     •  | Operates the electric motor | 
 
In response to the controller, the motor moves a connecting strap. The
connecting strap is attached to the cruise control cable. The cable moves
  the throttle linkage in order to vary throttle position in order to maintain
  the desired cruise speed. The cruise control module contains a low speed
 limit.  This prevents the system engagement below a minimum speed of approximately
  40 km/h (25 mph). The module is controlled by mode control
 switches.  The mode control switches are located on the turn signal lever.
 The cruise  control is in the standby disabled mode until all conditions
inconsistent   with the cruise control operation are cleared.
Ignition voltage is supplied from the CRUISE fuse, through CKT 739
to terminal F of the cruise control module. The cruise control module
  receives ground at terminal E through CKT 1150 and from G201.
  When the slider switch is moved to the ON position, battery voltage is applied
  through CKT 397 to terminal A of the cruise control module
 connector.
If the brake pedal is not depressed, battery voltage is present from
CKT 739  through the cruise control release switch and CKT 86
  to the module terminal D. If the brake pedal is depressed, battery
  voltage is supplied  from the STOPLAMP fuse, through CKT 140,   the
stoplamp switch and CKT 17 to the module terminal G. Terminal G
  must see current flow through the center high-mounted stop lamp (CHMSL)
  bulbs in order for the cruise to operate and disable properly.
When the slider switch is moved to the R/A position, battery voltage
is applied through CKT 87  to terminal C of the module. With
  the set switch depressed, battery voltage is present through CKT 84
  to module terminal B. Cruise control module connector terminal K
  is the speed signal terminal through CKT 389. In operation, voltage
  will oscillate between a high of 4 to 5 volts and a
 low  of near ground. Terminal J is used in order to signal the powertrain
control  module (PCM) when the cruise control is engaged
through CKT 85.   The PCM will then determine the correct shift pattern
for the transmission.   Terminal H is used by the PCM through CKT 83,
 in order to  inhibit  cruise control when conditions not consistent with
cruise control  operation  are present. The PCM will inhibit the cruise control
when any of  the following  conditions exists:
|     •  | The vehicle speed is less than 40 km/h (25 mph). | 
 
|     •  | The transaxle range switch is in one of the following positions: | 
 
|     •  | An over/under battery condition exists. | 
 
|     •  | The engine is running at low RPMs. | 
 
|     •  | The engine is running at high RPMs (Fuel cut-off). |