My dad and I were checking the voltages and currents of some of the fuses that are under the hood because my battery is being drained by something when the car is off. The only one we found with any voltage or current was the spot for the "Back Up" system. We registered about 11.5 volts and 2.5 milliamps. Anyone know what the "Back Up" system is and if it is normal for it to be drawing current when the car is off? Any help is appreciated.