using the motor voltage u mot measured at the starting time of the brake motor 2 when this current is determined the simplification of assuming a system of the first order is sufficient the inductance of the brake motor 2 can be ignored because the measuring time is significantly longer than the expected time constant u03c4 and owing to the fact that at high temperatures the mechanical time constant u03c4 is very much greater than the electrical time constant the expected current i at the predetermined time t 0 which forms the time for the determination of the load free release is determined using the exponential function in order to calculate the current profile i t the no load current i l must be added again at the predetermined time of the determination of the load free release for example after t 0 80 ms the calculated current i t 0 is compared with the current i mot which is measured at this predetermined time t 0 for this purpose a safety threshold is preferably applied which is added to or subtracted from the calculated value if the comparison reveals that the measured current is at the level of i t 0 it can be assumed that the automatic parking brake 1 is in the state of load free release at the predetermined time t 0 and the recalibration can be initiated if on the other.