A method and system are disclosed for estimating cell voltage excursion in a battery pack in the presence of a sensing fault in which actual cell voltages of first and second battery cells in a block of battery cells become unknown or missing. The sensing fault is detected, and a cell voltage is determined for each cell in the block other than the first and second cells. The method also includes measuring a block voltage, calculating an average cell voltage in the block, and estimating that the first cell is equal to the calculated average cell voltage. All excursion or deviation of the measured block voltage from a sum of the cell voltages and the estimated cell voltage of the first cell is assigned to the second cell. A control action is executed using the estimated cell voltages, including selectively enabling or disabling functionality of the battery pack.