This paper contributes to the research on dynamics and heterogeneity of product innovation in embedded software in the case of Japanese automotive software (ASW). Functions of embedded software are realized by being embedded into hardware, so if we know the functions of an embedded system, we know the functions of its embedded software. Therefore, based on the advantage of using patenting in large third countries as a good proxy measure for national innovation activities, we use ASW related patents in the USPTO patent database as an indicator of ASW product innovation. The results show that heterogeneous actors have had different roles and propensities to innovate in several fields of ASW functions, namely power train control, battery and electric power control, safety control, body control and ICT system over the period 1981 to 2010. There was a shift beginning in the early 1990s, when suppliers were becoming more and more important in product innovation of ASW. Increasing cooperation happened mainly between the automotive makers and suppliers, especially big suppliers. To conclude, the heterogeneous requirements for real-time operation and accumulation of specific knowledge that are technologically difficult and complex are the main reasons of heterogeneity of product innovation in embedded software.