Function
The BARO sensor is located in the PCM and measures the ambient air pressure. The further functioning is similar to that for the Bosch common rail system.
Note: some versions (with fixed-geometry turbocharger) are not equipped with a MAP sensor for detecting the actual boost pressure. In these versions, the BARO sensor signal is used together with the engine speed and air mass signals to calculate the boost pressure.
Effects of faults
In the event of a fault, the signal from the MAP sensor is used to determine the ambient air pressure. If both sensors (BARO und MAP) are defective, the PCM uses a substitute value. In this case, the injected fuel quantity and therefore engine performance is significantly reduced.
Diagnosis
The PCM continuously checks the BARO sensor for short circuits (to ground and positive) and for open control loop.
As already described with regard to the MAP sensor, a comparison (plausibility check) is performed between the BARO sensor and the MAP sensor when the ignition is switched on (engine off).
If the PCM detects a fault during the plausibility check, the system assumes that the MAP sensor is defective. As the BARO sensor is integrated into the PCM, it is assumed that malfunctions of the BARO sensor are extremely improbable.
Depending on the vehicle version a faulty BARO sensor may have a greater or lesser effect on the exhaust emissions. Depending on this fact the component can be classified as MIL active or non MIL active.
Typical malfunction limits:
โข Sensor voltage 4.36 V
Possible diagnostic trouble codes: P2227, P2228, P2229.