Some engine versions with emission standard IV (without diesel particulate filter) are equipped with an intake manifold flap servo motor.
In these versions the intake manifold flap only serves to restrict the intake air for more efficient exhaust gas recirculation (more efficient exhaust gas recirculation at lower engine speed/load ranges).
If the system does not provide a sufficient quantity of exhaust gas at low engine speeds/loads despite a fully-opened EGR valve, the intake manifold flap is closed by a specified value.
The resulting low pressure causes more of the exhaust gases to be drawn away from the EGR valve. In this way, the EGR is adjusted to the required amount. The current setting of the intake manifold flap is determined by the MAF sensor (closed control loop).
Effects of faults
Intake manifold flap servo motor faults lead to the EGR system being switched off.
Diagnosis
Based on the power consumption of the servo motor, the PCM detects whether actuation is within the limits. In this manner, the system detects a short or open circuit.
Since the EGR system is deactivated in the event of a fault, this is a MIL active component.