From what I am finding, that looks like a service fault code. Please call Support at 1-800-821-2797.
I have had my Xerox Phaser 6510 for about a year, and about a month ago, it started throwing out Fault Code 124-324. It suggests turning the machine off and on again. Doing this doesn't change anything. This is the only message the printer displays, and it will not do anything, including printing a test page. From what I have researched, that specific code is related to billing sorters on larger macines. This machine doesn't have a billing sorter. What should I try to do?