Current and future automotive systems are becoming more complex than ever. They consist of different subsystems such as engine, transmission, cooling module, driveline, controls, HVAC, active and passive safety systems. The hardware and the software development for each of these subsystems have different timelines. The subsystems are usually developed by different teams within the company and the suppliers. A full functional vehicle level system model is necessary to understand the complex interaction of these subsystems. Model.CONNECT was used to build a vehicle level system model by connecting driveline, cooling module, powertrain, thermal controls and two-phase refrigerant loop models with minimal effort. This paper demonstrates how integrated system level co-simulation facilitates front loading of virtual vehicle development. The integrated model was validated by comparing model results with experimental data obtained from EPA and SCO3 fuel economy drive cycles.