Cause

Colour regustration sensor (C-4631 - Yellow, C-4632 Magenta, C-4633 - Cyan, C-4634 Black)

Resolution

1    Power the machine OFF from the main switch leaving the sub switch ON.
2    Turn main power switch ON while pressing the Utility/Counter key. Keep holding it till the comes up in Service mode.
3    Press 02 Process Adjustment
4    Press 02 Drum Peculiarity
5    Select the Toner Densit Revert, if the readings are very high on any of the colours perform as below for that colour
6    Select 02 and run the Gamma Automatic Adjustment, a message "Completed" will appear in the top left when finished.
7    Exit Service mode to return to normal operation