This paper includes analysis results for the control strategy of the Peugeot 3008 Hybrid4, a diesel-electric hybrid vehicle, under different thermal conditions. The analysis was based on testing results obtained under the different thermal conditions in the Advanced Powertrain Research Facility (APRF) at Argonne National Laboratory (ANL). The objectives were to determine the principal concepts of the control strategy for the vehicle at a supervisory level, and to understand the overall system behavior based on the concepts. Control principles for complex systems are generally designed to maximize the performance, and it is a serious challenge to determine these principles without detailed information about the systems. By analyzing the test results obtained in various driving conditions with the Peugeot 3008 Hybrid4, we tried to figure out the supervisory control strategy. The engine of the vehicle is mostly turned on or off on the basis of the SOC, demand power, and vehicle speed according to the driver mode. If the engine is turned on, the front axle driven by the engine generally provides all propulsion power. Further, when the engine is on, the generator torque is controlled to satisfy the desired battery power, while the power is determined by SOC according to the driver mode. The control targets for the vehicle components are basically determined by these concepts. Several additional analysis results are provided such as creep torque control, engine on/off under different thermal conditions, and the energy consumption of the electrical accessories. The information provided in this paper should be helpful in understanding the system behavior of the Peugeot 3008 Hybrid4.