Circuit Operation

The Cruise Control System works a mechanical linkage to an adjuster assembly. This adjuster assembly is also shared by the Acceleration Slip Regulation System (ASR) (refer to Brakes and Traction Control for more details). The linkage is controlled by a diaphragm moved by a vacuum applied to one side. A solenoid driven valve connects the Vacuum Motor to a vacuum tank. Another solenoid valve vents the vacuum. The Cruise Control Module controls the Vacuum Motor and the adjuster assembly by pulsing these solenoid valves "ON" and "OFF."

One input to the Cruise Control Module is the vehicle speed. This input comes from the Engine Control Module (ECM)/Powertrain Control Module (PCM) after the ECM/PCM buffers the speed signal sent by the Vehicle Speed Sensor. If the actual speed signal is different from the speed that was set into and remembered by the Cruise Control Module, the Cruise Control Module gives off pulses to change the vacuum and return the vehicle to the set speed. Other inputs to the Cruise Control Module are from the Cruise Switch and the Set Switch. Also, there is a disengage input to the Cruise Control Module. This input, when voltage is applied to it, disengages the Cruise Control System until voltage is removed and the Resume Control activated. Voltage is applied to this input by either the Cruise Release Clutch Switch (Manual Transmission), the Brake Pedal Cruise Release Switch or the Cruise Control Cut-Off Relay (as commanded by the ASR System). When voltage is applied to the disengage input by the Brake Pedal Cruise Release Switch, vacuum is released also, and the Cruise System will have to reset using the SET Switch when the brake pedal is released.

The two outputs of the Cruise Control Module operate the coils of the vacuum valve and the vent valve. Both valves are found in the Cruise Control Servo. These valves move the servo mechanical linkage by means of the Vacuum Motor. The Servo Position Sensor coil senses the position and motion of the Vacuum Motor. It feeds this information back to the Cruise Control Module to provide smooth performance while the vehicle is in Cruise Control.