A printing device comprises a print head, imaging member, and a moveable sensor array. The print head is configured to deliver marking material to the imaging member as it moves in a process direction. The linear sensor array comprises a plurality of photo sensors configured to scan the imaging member. The photo detectors of the linear sensor array define a sensor axis that is substantially perpendicular to the process direction. The linear sensor array is configured to move along the sensor axis between a first position where the sensor array scans one portion of the imaging member and a second position where the sensor array scans another portion of the imaging member. If a fault is detected during calibration of the sensor array, the moveable sensor array may be used to determine whether the source of the fault rests with the imaging member or the sensor array.