Service-oriented architecture is a possible solution to the increasing complexity of automotive software systems. We conduct a systematic mapping study investigating the use of service-oriented architecture in automotive software. This study aims at providing information on publication trends, available architectural solutions, main benefits and challenges in automotive service-oriented architecture. From an initial set of 341 peer-reviewed publications, we selected 28 primary studies, which we classified and analysed using a thorough protocol. We provided both quantitative and qualitative analyses using vertical and orthogonal analysis. We found that there has been a significant increase in the number of publications recently, and that the studies focused on defining functionalities and data flow between them. Functionality was found as the most recognized benefit when applying service-oriented architecture in the automotive domain, while security, safety and reliability are the most recognized challenges.