The cruise control module contains a stepper motor. The stepper motor positions a cable connected to the throttle. The cruise control cable operates the throttle in the same manner as the accelerator cable. The cruise control cable is wound on a reel in the module. The stepper motor turns the reel in one direction or another in order to control the position of the throttle. and thus control vehicle speed. When the cruise control is idle or disabled, the stepper motor is disengaged. When the stepper motor is disengaged, the cruise control cable is free to move in accordance with motion of the accelerator cable. When the cruise control is on, the stepper motor will engage the cable and position the cable to maintain a minimum speed. Use of the accelerator in order to increase speed is permitted, but release of the accelerator will not decrease the speed to less than the speed set by the cruise control module. The cruise control module will not limit the speed when the vehicle coasts down a hill.

The cruise control module is powered with the ignition switch in the RUN position by the CRUISE Fuse 6 through CKT 41 (BRN) wire. The CRUISE Fuse 6 also provides operating voltage for the cruise control switch located on the steering column in the multifunction lever. The cruise control module is grounded by CKT 451 (BLK/WHT) wires at grounds G103 and G104.

The cruise control switch consists of two switches. The cruise control switch provides three separate inputs to the cruise control module. The cruise control switch consists of a S/C (Set/Cruise) pushbutton and a three-position Off-On-R/A slider switch. With the three-position Off-On-R/A slider switch in the center ON position, the ON input is delivered by the CKT 387 (GRY) wire to the cruise control module. This input enables the cruise control module response to the other two switch inputs. Placing the cruise control switch's Off-On-R/A slider switch in the OFF position while cruise control is engaged will disengage the cruise control system without retaining speed setpoint memory.

The S/C pushbutton input is delivered by the CKT 84 (DK BLU) wire. The pushbutton input must be present in order to initially engage the cruise control. With cruise control not yet engaged, this pushbutton input sets the speed at which the cruise control will operate until otherwise directed. Once cruise control is initially engaged, this same set input can be used for two other functions. If the S/C pushbutton is pressed for a short time (less than 1 second), the input will cause the cruise control module to tap-down the speed setpoint by 1.6 kph (1 mph). Repeated tap-down operations can be performed as long as the vehicle speed remains above the lower limit for cruise control operation. Cruise control will not engage with vehicle speeds lower that 40 kph (25 mph). If the pushbutton is pressed for a longer period of time, the cruise control module will disengage the throttle and wait for the pushbutton to be released and the vehicle will coast. When the pushbutton is released, the cruise control module will reengage with the current speed as the control setpoint.

The R/A (Resume/Accelerate) input is provided on the CKT 87 (GRY/BLK) wire. The Off-On-R/A slider switch's R/A position is a momentary contact switch like a pushbutton. This switch input also has three functions. If the cruise control was operating and the disengaged by actuation of the brake pedal, this input will cause the cruise control module to resume operations at the previous speed set speed setpoint. If the engine has been turned OFF or the cruise control switch has been placed in the OFF position since the previous operation, no response will occur.

With the cruise control already engaged, an R/A input will tend to cause the vehicle to accelerate. If the switch is pressed for a short time (less than 1 second), the cruise control module will tap-up speed by 1.6 kph (1 mph). The tap-up operation may be repeated. If the switch is actuated for a longer period of time, the cruise control module will increase vehicle speed (accelerate) over time until the switch is released. When the switch is released, the current speed becomes the new speed setpoint. Accelerating with the cruise control switch while the vehicle operates under heavy load or prolonged accelerating with the cruise control switch may cause the automatic transmission to downshift. As with the use of the accelerator, engine damage may occur if the engine speed becomes excessive.

The cruise control module monitors two stoplamp switch inputs. Voltage is supplied to the stoplamp switch pin F from BRAKE Fuse 18 (Hot in RUN). The stoplamp switch sends an enable signal from pin C to the cruise control module over the CKT 420 (PPL) wire. With the brake pedal released, this signal is present, and the cruise control module operations may be engaged. The loss of this voltage, as when the brake pedal is actuated, will cause the cruise control module to disengage. The cruise control module retains the previous speed setpoint information in case operations are resumed. Intermittent opens or shorts to ground on the CKT 420 (PPL) wire will also cause the cruise control to disengage.

The other stoplamp switch input on the CKT 17 (WHT) wire is used to check stoplamp switch operation before engaging the cruise control. Power to stoplamp switch pin B is available when the ignition switch is in the RUN position through the CKT 140 (ORN) wire. After the ignition switch is placed in the RUN position, the brake pedal must be actuated in order to provide cruise input though the CKT 17 (WHT) wire. After stoplamp switch operations are confirmed, the cruise control module will respond to a set input.

The cruise control module monitors a vehicle speed signal from the VCM on the CKT 817 (DK GRN/WHT) wire. This 4000 pulse per 1.6 km (1 mile) input is used for setting and for controlling vehicle speed. This input will generate an RMS voltage of between 0-5V depending on speed when measured with a high impedance voltmeter.

The cruise control module signals the VCM that the cruise control is engaged on the CKT 396 (LT BLU) wire. The VCM may use this information in control of transmission shifting. If a new VCM is installed, it must be told that the cruise control module is present but engaging, disengaging and reengaging the cruise control. Refer to Engine Controls for the specific engine.

The cruise control system for the diesel engine operates in much the same manner as that for the gasoline engine. However the fuel flow is controlled electronically for the diesel engine rather that air flow control by the throttle cable as with the gasoline engine. The functions of the gasoline engine's cruise control module are incorporated into the diesel engine's PCM. The PCM also provides a high speed engine speed limit which is not available in the gasoline engine's cruise control module. Diagnostic Trouble Codes DTC-71 for prolonged voltage (over 25.5 seconds) on the S/C input and DTC 76 for prolonged voltage on the R/A input are also provided by the PCM. The PCM will disengage the cruise control for either DTC. Refer to Engine Controls.