Master Cylinder ABS code #62

I pulled the ABS code. It's code #62, "Low Accumulator Precharge". So... from what I'm told, there is a resevoir that stores pressurized air required for the ABS system to function. It appears that it's not holding the charge. There may be a leaky valve or something... At least this is what I've been told. Anyways, is this repairable, or am I looking at replacing the whole unit?