Barometric Pressure Sensor: Description and Operation

Barometric Pressure Sensor:

PURPOSE
The Barometric Pressure (BP) sensor measures atmospheric pressure and sends this information to the Powertrain Control Module (PCM). The PCM uses this data to compensate for changes in the amount of oxygen in the air as the vehicle changes altitudes. The PCM alters the air/fuel ratio, ignition timing, and EGR flow to compensate for these changes.

CONSTRUCTION
The BP sensor utilizes a pressure sensitive piezoelectric disc. The electrical characterics of the disc change with the amount of pressure applied to it.

OPERATION
Atmospheric pressure is converted to an electrical signal by the piezoelectric disc. This signal is then converted by circuitry within the BP sensor to a frequency modulated output signal.

The output frequency of the BP sensor varies directly with atmospheric pressure and indirectly with altitude. As the altitude of the vehicle increases, the atmospheric pressure decreases, and the BP sensor output frequency decreases.

The BP sensor uses a three wire connection.

- VREF is a 5.0 volt reference signal from the PCM and is used as a power supply by the BP sensor
.
- BARO SIG is the BP sensor output.

- SIG RTN is the sensor ground.

RELATED DIAGNOSTIC TROUBLE CODES

DTC 22/126 - BP/MAP sensor output out of range during self-test (140hz-160hz).