Hybrid Electric Vehicle (HEV) Controls Development is an important aspect to realize the goals of Powertrain Electrification i.e. fuel economy and emission improvement. Keeping that in mind, development engineers need to formulate numerous control strategies. Once the control strategy is evaluated and frozen, it typically does not change from one vehicle model application to another. However, it may happen that Electronic Control Unit (ECU) manufacturer may change depending on the sourcing strategy. Therefore, in order to maintain uniformity, it may be required to compare control strategy of a finished ECU product frozen for one model application to be compared with new ECU sourced through another manufacturer. This paper discusses a methodology to compare control strategy of two ECU’s sourced from different ECU manufacturers with identical control requirements. The scope of comparison is limited to Engine Auto-Stop-Start function using a modular platform on dSPACE Hardware In loop setup. One of the controllers has been tried and tested in the market and has proven to be reliable. The other new controller is evaluated against the robust and already proven controller. The effect of both the control strategies has also been discussed as to how they affect the states of different associated subsystems.