Toner concentration failure 393-360

[Reeves]

I have a xerox wc 5955 gives fault code 393-360 I reset the fault through 501-359 from 17 to 0 but still giving this code after 5 to 10 copies I even added developer material but the fault code keeps coming back
What could be the problem

[xcopytech]

Did you follow service manual procedure, measure voltage on p/j 766 pin 1 and pin2

[rockdude]

Generic Toner ?