There is described a method for monitoring a drive device for a defective sensor signal from a first sensor of the drive device and to a monitoring device which is suitable for this purpose. Although sensors operate reliably, sensor errors which may give rise to significant damage if they are not detected may arise. Monitoring the sensor makes it possible to increase the reliability of the drive device. The sensor signal from the first sensor is compared with a sensor signal from a second sensor in such a manner that the first sensor is monitored. In this case, the monitoring device is intended, in particular, for a sensor having a sensor disc.