Defect SymptomTransfer Belt Module (TBM) Leak refers to wide, dark (Gray, Purple, or mixed color) bands, located near the center of the page, extending from the top to the bottom of the page.
Troubleshooting 
Perform the "Color Adjust" procedure in the "Quality" menu.
If the defect is a single color (Cyan, Magenta, Yellow, or Black), replace the toner cartridge.
If the defect is gray, purple, or some other mixture of colors, remove the transfer belt module and determine whether it is full of toner.
The transfer belt module will leak when full, and must be replaced.
Contacting Lexmark Please contact Lexmark Technical Support if you need additional assistance.
NOTE: When calling for support, you will be asked for your machine/model type and serial number (SN). If you need help locating your printer's model type and serial number (SN), How to Locate the Serial Number, TLI, Config ID, and Machine Type on the Lexmark C734, C736 or X734, X736, X738 Color Laser Printers.
Please call from near the printer in case the technician on the phone asks you to perform a troubleshooting task on the printer.
LEGACY ID: SO6627