Barometric Pressure Sensor: Description and Operation

CIRCUIT DESCRIPTION
The BARO sensor is built into the Engine Control Module (ECM). This is a semiconductor pressure sensor with properties which cause its electrical resistance to change when stress is applied to the sensor's crystal (silicon) (piezoelectric effect). This sensor 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 these 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).