one vehicle wheel is disconnected from a differential while the vehicle is in a front wheel drive mode . a controller checks for a malfunction of the differential while the vehicle is in the front wheel drive mode and in response to a request to enter an all wheel drive mode . if speeds of the other vehicle wheel and the differential input indicate that the malfunction is present , the all wheel drive mode is disabled and the driver is informed . if fluid temperature indicates a risk of the malfunction , all wheel drive mode is temporarily disabled and the driver is informed . if the temperature condition continues to be present for a predetermined duration , the all wheel drive mode is disabled .