If your car batt goes dead and you have to replease it, try to have an outside sorce of power to continue replenishing the car with 12 volt so as not clear the radio memory and make an err code,my advice is to get a batt buster,and supply voltage to the terminals of the batt while you are removing (replacing) the batt,that way you won't loose mem,or install a backup 12 volt to the cigar lighter socket, that's what I did and had no problem