This slide shows an analysis of some of the commonly seen failure modes in electric power steering motor systems. Loss of steering indicates that the electric power steering system is unable to assist in steering the vehicle. Most vehicles have a mechanical steering column that can continue to steer the car, albeit with more effort. There are several failures that can cause loss of steering.  A short or open circuit in the motor coil, a short or an open circuit in the FETs driving the motor coils, a damaged motor driver, failure of the microcontroller or failure of the microcontroller power supply, or incorrect configuration of one of the components in the system. Another hazard is unintended steering, a condition in which the electric power steering system steers without any input from the driver. This failure could be caused by an MCU that has browned out and is not computing correctly, or it could be due to a failure in the digital logic in any of the other components. A third hazard is steering in the wrong direction. The causes for this are similar to the conditions seen in unintended steering.