Virtualization allows the simulation of automotive ECUs on a Windows PC executing in a closed-loop with a vehicle simulation model. This approach enables moving many development tasks from road or test rigs and HiL (Hardware in the loop) to PCs, where they can often be performed faster and cheaper. Technical challenge: How to port ECU tasks and basic software to Windows PC with reasonable effort, so that key development tasks can be performed on a PC, without the need of accessing real hardware such as vehicle prototypes, test rigs or HiL facilities. This paper presents a new solution for the use case of ECUs developed within the emerging AUTOSAR standard: First, the AUTOSAR authoring tool AUTOSAR Builder (Dassault Systèmes) is used to design the application software and system aspects of a single ECU or an distributed embedded system which is then stored as AUTOSAR XML descriptions. The application code can either be developed in the AUTOSAR Builder environment or auto-generated by tools such as Embedded Coder (MathWorks), TargetLink (dSPACE) or Ascet (ETAS). Once tested in AUTOSAR Builder, selected software components or compositions can be exported including an AUTOSAR OS (Operating System) and RTE (Run- Time Environment) as an FMU (Functional Mockup Unit). FMU [4] is a new exchange format for models that has been developed in the EU-funded MODELISAR project (2008 - 2011) and since then gained considerable acceptance across multiple industries and tools. The FMU can then be imported into the virtual ECU tool Silver (QTronic), where it can be co-simulated with vehicle models originating from a wide range of simulation tools, including Dymola, SimulationX, MapleSim and AMESim. Vehicle models are again provided as FMUs, or via proprietary binary export formats, typically Windows DLLs. Tools for measurement and calibration such as CANape (Vector Informatik) or INCA (ETAS) can then be connected to the virtual ECU running on PC, to directly measure or tune its parameters, like an engineer would do in a real car. Virtual ECUs are also used to move testing activities from test rigs and HiLs to Windows PC.