Vacuum Control Solenoids
Remove solenoid. With no power to solenoid, air should be able to flow between port "B" and "C" (vent). See Fig 1 . Using vacuum tester apply vacuum to port "A", vacuum should hold.
Apply battery voltage to solenoid. See Fig 1 . Air should be able to flow between port "A" and "B" only. If solenoid does not test as specified, replace solenoid.