Barometric Pressure Sensor: Description and Operation

PURPOSE / OPERATION
The barometric pressure (BARO) sensor is built into the ECM. This is a semiconductor pressure sensor with properties which cause its electrical resistance to change when stress is applied to the sensor's silicon crystal (piezoelectric effect). It is used to detect the atmospheric (absolute) pressure and outputs corresponding electrical signals. Fluctuations in the air pressure cause changes in the intake air density which can cause deviations in the air-fuel ratio. The signals from BARO sensor are used to make corrections for the fluctuations.
If the ECM 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).