A method is provided for predicting a loss of high-voltage isolation within a hybrid, electric, or fuel cell vehicle. The method includes recording the equivalent resistance between a vehicle chassis and a high-voltage bus, detecting a trend in the measurements, and predicting when the resistance will drop below a threshold value. The method also includes issuing a warning or message to the owner/operator when the predicted remaining number of events drops below a predetermined number and/or when the resistance drops below the threshold. Additionally, an apparatus is provided for predicting a high-voltage isolation fault comprising a controller having an algorithm for predicting the fault, a high-voltage bus and bus components, and a reporting device for reporting the fault and/or predetermined number of remaining events. The controller is configured to initiate the algorithm and record a series of equivalent resistance measurements taken between the vehicle chassis and high-voltage bus.