California Models
The vacuum switching valve (VSV) has 3 three-way ports, 2 of which are actuated by solenoid plunger. Solenoid plunger is energized when catalyst temperature is more than 1350°F (730°C). When energized, VSV connects chamber "B" of air switching valve to intake manifold, permitting manifold vacuum to be applied to chamber "B". When plunger is de-energized, it plugs port so chamber "B" is connected to diaphragm chamber "A" of air switching valve.