Cruise Control Systems: Operation: Servo

Servo consists of solenoid valve body and vacuum chamber. Solenoid valve body contains vacuum solenoid, vent solenoid and dump solenoid. Vacuum chamber contains a diaphragm connected to throttle linkage. PCM supplies power to solenoid valve body through brake switch. PCM uses duty-cycle controlled ground to operate vacuum and vent solenoids. Dump solenoid is powered when system is on. If power is interrupted, dump solenoid will vent system.