The actual trend in the transport industry is to have electronic system without mechanical back-up, so-called "by-Wire" systems. Micro-computer control steering, brakes, power train etc... Robust protocols are needed to make these micro-computer communicate. They hould be fault-tolerant and yet not let the micro-computer split into disjoint communicating subsets. TTP is a time-triggered protocol that has been proposed for the automotive industry. In this paper we investigate the clique avoidance mechanism of TTP/C, the last version of TTP, and prove that it is effective, even maybe too strong.