While it isn't an absolute diagnosis, typically if you get an alarm and the driver does not get excessively hot it is the motor, if the driver gets hot and doesn't alarm or emits an abnormal alarm (strange pitch or very soft) it is the driver. The place to feel for the heat is at the top bracket, there is a heat sink under there and a bad driver will get quite hot in a about 15 seconds. Otherwise, you can get a more accurate diagnosis with a watt meter, on a 6100 a bad driver will typically show as a very high wattage, like 150-400w. A bad motor will show as a very low wattage like 0-30w but occasionally a bad motor shows a wattage in the range of 80-115w, it depends on the fault. A lower wattage means half the coil is dead, a higher wattage means a short is keeping both coils on all the time.