Steer-by-Wire steering systems (SbW) are expected to be the next generation of steering systems and fulfill all requirements for vehicles to perform SAE level 4/5 autonomous driving tasks. However, SbW faults can significantly impact all traffic participants' safety with a missing mechanical fallback path and reduced attention of drivers and passengers in autonomous driving situations. In this paper, we utilize fault injection techniques to derive requirements for safety mechanisms and E/E architectures in SbW. We first analyze faults in the SbW on different system layers, which can lead to a hazard, for instance, the loss of steerability. Afterward, we present a fault-tolerant SbW E/E architecture and investigate safety mechanisms that can ensure dependability. We apply fault injection techniques in the SbW system in a case study to derive requirements for safety mechanisms that detect and handle faults sufficiently. Thereby, we evaluate the lateral vehicle dynamics behavior in representative driving maneuvers under the effect of fault injections. We derive requirements for safety mechanisms and the E/E architecture from our findings. To conclude the paper, we compare our findings with requirements for safety mechanisms in current EPS systems and discuss the applied method.