Theory Of Operation

The Barometric Pressure (BARO) Sensor is internal to the Powertrain Control Module (PCM). The internal BARO Sensor reading gives the PCM an indication of the current atmospheric pressure during driving conditions. The PCM uses this information to help calculate fuel delivery. The PCM receives a BARO reading from the MAP Sensor with the ignition on, before the engine is cranking or running. This BARO reading from the MAP Sensor is then compared to the internal BARO Sensor by the PCM to run a rationality check.