Barometric Pressure (BARO) Sensor

The BARO sensor measures barometric pressure to estimate the exhaust back pressure.

For vehicles with a turbocharger intake pressure and temperature (TCIPT) sensor, the BARO value is inferred by comparing the TCIPT sensor, manifold absolute pressure (MAP) sensor, and turbocharger boost pressure (TCBP) sensor values at key on, engine off (KOEO). While driving, the BARO is updated by monitoring the TCIPT sensor when air flow volume is below 2 parts per million.

For direct injection vehicles, a BARO sensor is mounted internally to the PCM. The BARO sensor measures the barometric pressure to estimate the exhaust back pressure.

For all other vehicles without a BARO sensor, the BARO value is inferred by the PCM based on the volumetric efficiency of the engine, comparing the mass air flow (MAF) sensor and the ambient temperature values. The actual MAF value is used to calculate an inferred MAP value based on operating conditions and volumetric efficiency. At or near wide open throttle, the BARO value is calculated to be slightly higher than the inferred MAP value, with the difference calculated by the pressure drop across the throttle plate.