Cause

Toner Density Low (C-2451 - Yellow, C-2542 Magenta, C-2453 - Cyan, C-2454 Black)

Resolution

Step 1.
Power the machine OFF from the main switch leaving the sub switch ON.
Turn main power switch ON while pressing the Utility/Counter key. Keep holding it till the comes up in Service mode.
-02 process adjustment
-02 drum peculiarity
-06 toner revert - Select "All on" (When it completes, check values all should be as near as 1.26 as possible, keep running to get correct values). Return to previous screen.
-02 gamma automatic adjust (wait for adjustment to complete)