A monitoring device and a method for operating an idling automatic transmission of a motor vehicle having a torque converter which includes at least one pump wheel and a turbine wheel that are designed to transmit torque hydrodynamically from one to the other. The method includes at least the following steps of: determining a rotational speed of the turbine wheel; determining a load on the motor of the motor vehicle; and recognizing whether there is a blockage in the drive-train of the motor vehicle or whether the torque converter is running dry, as a function of the turbine rotational speed and the motor load detected.