An indoor gardening appliance includes a grow module that is seated on a turntable that is rotatably mounted within a grow chamber and is rotated by a drive assembly. A position sensing assembly monitors an angular position using two proximity sensors, such as Hall-effect sensors, mounted below the sump, and the turntable includes a plurality of proximity indicators, such as magnets, positioned at various circumferential positions on the turntable. A controller is configured to initiate rotation of the turntable from a first angular position, determine that the turntable should have reached a second angular position, e.g., based on the operating duration or drive signal of the drive motor, and identify a drive assembly fault upon determining that the turntable has not reached the second angular position.