The AUTOSAR standard is rapidly being adopted by automotive engineers for developing the software architecture and the firmware for automotive electronic control units (ECUs). AUTOSAR application consists of many components, two of which are; the software architecture that is a composition of AUTOSAR Atomic Software Components (AR A-S/W) and the behavior or implementation of each AR A-S/W. When such AR A-S/W implementation is specified using a modeling tool, it is referred to as AUTOSAR Behavioral Modeling. UML/SYSML is a widely used modeling language for specifying and designing software applications for aerospace, automotive, communications, consumer electronics, industrial controls and medical electronic systems and includes powerful behavioral modeling notations such as Statecharts and activity diagrams.In this paper we will quickly review the basic concepts that make up the AUTOSAR software architecture such as AUTOSAR Software Components and Software Composition, and the AUTOSAR Runtime Enviornment, then provide an in depth discussion of how we implement the behavior of an AUTOSAR S/W Component using UML/SYSML. This will include how to specify, design and generate implementation code using UML/SYSML while regarding the AUTOSAR Architecture. We will also show how this approach relates to the Internal Behavior sections defined in the AUTOSAR standard. Further we will explain how this approach can support reuse across domains, such that the user will be able to use the same UML/SYSML model to generate implementations for both AUTOSAR application or more traditional automotive environments.