Operation CHARM: Car repair manuals for everyone.
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Barometric Pressure Sensor: Description and Operation

Description
The barometric pressure sensor installed on the volume air flow sensor senses the barometric pressure and converts it into a voltage which is sent to the engine control module.
The engine control module uses this signal to compute the altitude at which the vehicle is running and corrects the air-fuel ratio and the ignition timing, thus improving driveability at high altitude.