System Operation

System operates when vehicle speed is 35-85 MPH, vehicle is in gear and clutch and brake are released. When conditions are met, PCM controls solenoid valve body to apply and release vacuum from vacuum reservoir to vacuum servo. Vacuum is stored in vacuum reservoir, located behind front bumper (Cherokee) or on right inner front fender (Wrangler). The vacuum servo contains a diaphragm connected to throttle linkage. Using input from Vehicle Speed Sensor (VSS), PCM adjusts vehicle speed. The vacuum and vent solenoids are supplied duty cycled ground by PCM to control vacuum to servo. The brake switch supplies power to dump solenoid and solenoid valve body when released. When brake pedal is applied, power is disconnected. The dump valve opens, releasing vacuum from servo.