The automotive industry is changing, digital components are gradually augmenting or replacing mechanical systems. The advent of autonomous and connected cars further increases the number and the complexity of embedded electronic systems, which poses new challenges. Indeed, compared to conventional vehicles, these highly technological objects have an increased role in the safety of their passengers and their environment. The requirements in terms of reliability and safety are thus also increased. To approach this new era, manufacturers must adapt their methods and invent new ones. The thesis proposes a method to meet some reliability and security related challenges that the limitations of the traditional approaches do not solve properly. It consists in introducing validation as early as possible in the software design and development life cycle, even before any executable or formal model has been produced. The method lays foundations for an iterative approach for the validation and verification of textual requirements and statements in order to detect errors, omissions or inconsistencies before implementation. This requirement qualification process is based on the translation of informal descriptions into formal models, followed by formal verification of generic or custom temporal logic properties. It also uses simulations and traces analysis for counter-example investigation. The proposed method is largely automated.