VAC - Vacuum (Differential Pressure) Sensor

Indicates voltage through vacuum sensor. Voltage reading is low when vacuum is low and increases as vacuum increases. With ignition on and engine stopped, reading should be under 1 volt, and with engine idling (high vacuum) reading should be over 3 volts.
Comparison of sensor readings with readings from known good sensor can be used to isolate malfunctioning sensor. Sensors have a color code tab in the connector cavity, and sensors with the same colored tab have identical calibration. Readings from sensors with like identification tabs should be the same to within +/- .4 volt.