Function
The boost pressure control valve is provided with a vacuum by the vacuum pump. Pulse-width modulated signals from the PCM control this vacuum via the boost pressure control valve. The controlled vacuum acts on the vacuum unit in the variable geometry turbocharger.
Effects of faults
In the event of a fault, boost pressure control is no longer possible. Therefore, the injected fuel quantity is limited (power output reduction) and the EGR system is deactivated.
Diagnosis
Boost pressure control operates in a closed control loop. The adjustment of the guide vanes of the variable geometry turbocharger is carried out via the boost pressure control valve. The boost pressure is controlled depending on requirements via the MAP sensor.
Monitoring of the boost pressure control valve comprises the following checks:
โข short circuit (to ground and positive) and open circuit,
โข for intermittent faults (for example loose contact),
Furthermore, boost pressure control valve or vacuum system faults are detected by the MAP sensor. Boost pressure control valve faults are detected by the output stage in the PCM via the power consumption of the boost pressure control valve.
As the EGR system is deactivated, the NOX emissions increase sharply. As a result, EOBD limits are exceeded. Therefore this is a MIL active component.
Possible diagnostic trouble codes: P0045, P0047, P0048, P2263