Abstract: A method and apparatus for providing hybrid functionality aboard a vehicle having a high voltage (HV) energy storage system (ESS) electrically connected to a VITM and a battery disconnect unit (BDU) including a precharge contactor and a high voltage (HV) contactor, a voltage sensor and a controller is provided. The method includes detecting an ESS/HV bus data fault, measuring and storing an initial HV bus voltage, closing the precharge contactor in the BDU, measuring a present HV bus voltage when the precharge contactor has been closed a predetermined short time and indicating if an actual ESS/HV bus fault exists, measuring the present HV bus voltage until either the present HV bus voltage is greater than the predetermined high voltage indicating that no actual ESS/HV bus fault exists or the time the precharge contactor is closed is greater than a predetermined maximum time indicating that an actual ESS/HV bus fault exists.