A hydrostatically driven vehicle has an engine operating a variable displacement propel pump, a displacement of which can vary based on an angle of a rotating swashplate, such that a fluid flow impelled by the pump transfers power to at least one propel motor rotating a wheel of the vehicle. An electronic controller of the vehicle senses an operating parameter of the system, for example, the angle of the rotating swashplate or the direction and speed of rotation of the propel motor with a sensor to yield an actual signal, and relays the actual signal to an electronic controller. The controller determines a desired angle for the rotating swashplate based on the control signal, and compares it to the actual signal from the sensor. Motion of the vehicle is stalled when the angle signal differs from the desired angle by a predetermined extent and for a predetermined period.