The X-by-Wire systems in cars can only be accepted if they provide at least the same dependability than the traditional ones. We propose a new approach to evaluate the impact of the EMI perturbations on the dependability of an X-by-Wire architecture. The considered X-by-Wire architecture is distributed around a TDMA-like communication protocol whose main peculiarities are explained. So a perturbation causes the loss of a communication cycle with a certain probability. The vehicle level failure is then defined as the consecutive loss of a certain number of communication cycles. Its reliability is modeled as that of the well-known “consecutive-k-out-of-n:F systems”. A case study, together with the EMI perturbations collected on the roads in France, is used to illustrate our approach.