Abstract This paper outlines the modeling process in SysML (Systems Modeling Language) in context of MBSE (Model Based Software Engineering) as well as the MBD (Model-Based Design) in Simulink and we compare the models to get useful information into software. For this goal, we propose the use of an RM/SM tool (Requirements Management and Systems Modeling) (3SL Cradle) and Matlab/ Simulink to model the system, do the system validations, and finally embed the generated code. For automotive systems, the development process is visualized through the V-Model, which leads to the right choice of components, the integration of the system and the project realization. The first step in V-Model handles the requirements management for the development, i.e., the requirements for a project will be collected in respect to the stakeholder’s needs and system limitations. Then, the next steps consist of modeling the system based on its requirements, going through simulation, system validation through Model-In-the- Loop (MIL), Software-In-the-Loop (SIL), Processor-In-the-Loop (PIL), and Hardware-In-the-Loop (HIL) tests. For this paper, the chosen modeling language was SysML for the MBSE point of view because it aims to standardize Modeling Design, by unifying diverse modeling languages used by engineers. This language also supports specification, analysis, design, verification, and validation of systems. To get executable models, we use Matlab/Simulink models that are largely used by the Original Equipment Manufacturers (OEMs) to develop new products. Our approach addresses the V-Model through SysML and MBD in Matlab/Simulink towards software validation. To achieve that, we use the commercial RM/SM tool that is used to collect stakeholder’s and system requirements. It provides a SysML design section as well where SysML models can be developed according to project requirements. One of the objectives in using the commercial tool is that it will be possible to analyze the transition from models in RM/ SM tools to models for simulation, such as Simulink and offer a new possibility for OEM’s and suppliers to abstract system models into executable models. The main contribution of this paper is that the automotive software development process is showed from its concept to its realization in real systems. Introduction New products or new releases, versions, and adaptations of a product are designed with the costumers’ desires which are turned later into stakeholders’ requirements. After those phases, the development starts with the engineering teams. It means that it is necessary to have a link among customers’ desires, stakeholders’ requirements and the development teams. This link is provided by the systems engineer who will manage requirements and provide functional models to other engineers. In this paper, we outline this development process and describe the integration of a subsystem into a system. Our final target is a new software for a vehicle Electronic Control Unit. Towards this, we manage requirements and model the subsystem in SysML in Cradle, translate the SysML models into Matlab/Simulink models, do MIL test. In order to show the approach for software development, a Mobile Seat Platform (MSP) for coach buses was chosen. MSP is a new subsystem required by the Brazilian Government to be part of the bus body [ 1]. However, the development process for heavy duty vehicles does not follow a standardized manufacturing culture in the whole world [ 1], i.e., trucks and buses might have several differences regarding the production process worldwide although the functionalities remain the same worldwide. We try to develop a standardized development approach for coach bus systems adaptations. It is quite interesting to model an integration process for coach bus systems once it can be used in several countries. So, other buses manufactures may apply the same models for their own production.New Approach of Tools Appl