Patent ID: 8775016

Claim:
A method of operating of a motor vehicle comprising a drive aggregate ( 1 ), a transmission ( 5 ) and a hydraulic system, the transmission ( 5 ) comprising a number (N) of shift elements ( 9 ) which, for each engaged gear, a first required partial amount (M) of the shift elements are engaged while an unrequired second partial amount (N-M) of the shift elements remain disengaged, the hydraulic system comprising a main pump ( 8 ) being driven by the drive aggregate ( 1 ) of the motor vehicle, and an auxiliary pump ( 10 ), being drivable independently from the drive aggregate ( 1 ), the method comprising the steps of: testing, when the motor vehicle is at a standstill and a brake ( 13 ) is activated, a functionality of the auxiliary pump ( 10 ); operating the drive aggregate ( 1 ) at a rotation speed which is low enough that the main pump ( 8 ) cannot provide a hydraulic pressure for filling of the shift elements ( 9 ) of the transmission ( 5 ), but driving the auxiliary pump ( 10 ) to provide a required hydraulic pressure, for a defined gear, to completely engage all but one shift element of the first partial amount (M) of the shift elements required for the defined gear, and engaging the all but one shift element up to an engagement point; subsequently either engaging the all but one shift element, beyond the engagement point, or engaging at least one other shift element, of the second partial amount (N-M) of the shift elements which are not engaged for the defined gear, starting from a completely disengaged condition to a condition beyond its engagement point; and upon noticing a reduction of the rotational speed of the drive aggregate ( 1 ), concluding that the auxiliary pump ( 10 ) is functioning properly, but, in an event that no reduction of the rotational speed of the drive aggregate ( 1 ) is noticed, then concluding that the auxiliary pump ( 10 ) is improperly functioning.