A vehicle includes charger contactors configured to selectively electrically couple terminals for connecting to a charger to corresponding terminals of a high-voltage bus. The vehicle includes a precharge contactor configured to selectively couple a terminal of a battery to the high-voltage bus through an impedance element. The vehicle includes a controller programmed to command the charger contactors to an open state for a drive cycle and command the precharge contactor to close at a start of the drive cycle and, responsive to a voltage across the terminals for connecting to the charger changing from being less than a first predetermined voltage immediately prior to the precharge contactor being closed to being greater than a second predetermined voltage at a completion of precharging, inhibit vehicle operation and disconnect the battery from the high-voltage bus.