A control device is provided for an assembly of a motor vehicle body, which assembly can be moved between at least two positions, specifically at least between a position retracted to the maximum extent and a position deployed to the maximum extent, in particular a spoiler. The control device contains a first sensor which transmits a signal to an evaluation device, which determines the position of the assembly from the signal of the first sensor, in dependence on the rotational speed of a motor which serves to move the assembly, and a second sensor which monitors a deployed position of the assembly and transmits a corresponding signal to the evaluation device. The evaluation device corrects the signal provided by the first sensor when the assembly is at least temporarily located in the position monitored by the second sensor and the signal provided by the first sensor is outside a tolerance range.