Barometric Pressure Sensor: Description and Operation

The barometric pressure sensor is one of three sensors that make up the Volume Air Flow (VAF) sensor. The barometric pressure sensor is essentially a strain gauge used to measure atmospheric pressure. Inside the sensor is a metal diaphragm with a small wire attached. The diaphragm flexes according to changes in atmospheric pressure. When the diaphragm flexes, the wire attached to it stretches, changing the resistance of the wire. The Engine Control Module (ECM) applies five volts to the barometric pressure sensor and measures the voltage drop across the sensor. Sensor output is in volts and as atmospheric pressure decreases (higher altitudes), the voltage drop across the sensor increases.