Barometric Pressure Sensor: Description and Operation

PURPOSE / OPERATION
The Barometric Pressure Sensor sensor is built into the Engine Control Module. This is a semiconductor pressure sensor with properties which cause its electrical resistance to change when stress is applied to the crystal within the sensor. The resulting piezoelectric effect creates a resistance which alters a reference signal from the Engine Control Module in response to changes in atmospheric pressure. Fluctuations in the air pressure cause changes in the intake air density, which can cause deviations in the air-fuel ratio. The signals from Barometric Pressure Sensor sensor are used to make corrections for these fluctuations. If the Engine Control Module records Diagnostic Trouble Code "35", the fail safe function operates and the atmospheric pressure is set at a constant 101.3 kPa (760 mmHg, 29.92 in.Hg).