The process of developing new functions and software for powertrain embedded control units (ECUs) is undergoing a sea change. One of the reasons is the pressure to meet regulatory requirements (e.g. emissions, fuel economy) in addition to managing the normal growth in software complexity. Traditionally, the vehicle manufacturer (OEM) would write new specifications and hand them over to the software supplier (Tier1). This process required a substantial review and testing process at the OEM to ensure that the requirements were interpreted and implemented as indented. Today, a number of parties are involved in creating specifications (including the software supplier and 3rd party engineering companies), thus making the verification task even more complex. In this paper, we present a model-based approach that, if implemented uniformly over the complete development cycle, is shown to significantly improve the collaboration efficiency between the various parties involved and, therefore, reduce development time and effort drastically. This approach leverages the knowledge of the target ECU constraints from the beginning, i.e. during the modeling, simulation and rapid prototyping phases of development. By using the ECU-specific model libraries (e.g. interpolation and math functions) during rapid prototyping, the function developers are sure there are no surprises later. The new function models are now ready to be transferred to the ECU via automatic code generation by the OEM. The OEM can now hand over the object files together with additional interface files to the Tier 1 for integration into the final build. Since the models already use the production library functions, the integration task of the Tier 1 becomes a lot easier. In addition, an optimized code-generator (e.g. by using arithmetic services routines) for the target ECU is shared between the OEM and Tier 1, resulting in highly efficient code. After software integration and testing by the Tier 1, the OEM can now fine tune the calibrations needed for the final release. This approach has been successfully implemented in a current series production program for a commercial vehicle engine.