A method is provided for operating a hybrid electric vehicle including an internal combustion engine and an electrical system, which electrical system includes at least one electronic control unit, an engine-driven electric machine (operable as a motor for driving the vehicle or as a generator for supplying power to one or more electrical loads via a high voltage traction bus, and a high voltage battery pack coupled to the high voltage traction bus by at least one contactor arranged to connect the battery pack to the high voltage traction bus. If it is determined that the at least one parameter indicates a condition preventing the battery pack from being connected to the high voltage bus, the electric machine is operated in voltage control mode during operation of the vehicle until the condition is eliminated, whereafter the high voltage bus is pre-charged and the high voltage battery pack reconnected.