Lexmark X644E Service Manual - Page 209

7002-xxx Toner sensor service check Service tip: Check the print darkness menu setting before checking the toner sensor. This service check is intended to be used when a 929.xx Service Error displays. FRU 1 Developer drive assembly 2 Front harness cable 3 Toner sensor Action Incorrect operation of the developer drive assembly can cause the printer to display a 929.xx error code (Toner Sensor). Check the developer drive assembly for correct installation or, any sign of worn, loose, or broken parts. Check the toner sensor portion of the front harness cable to make sure it is properly seated into the toner sensor. If correct at both the sensor and system board (J15), check the continuity of the cable. If incorrect, replace the cable. The toner sensor cable is part of the front harness and part of connector J15 on the system board. Check the voltage at J15-11. It reads approximately +5 V dc. If incorrect, replace the system board. If correct, check the voltage at J15-12. It reads approximately +5 V dc with the system board removed from the printer. If incorrect, replace the system board. If correct, replace the toner sensor assembly. A bad ground connection between J15-13 on the system board and pin 3 on the toner sensor results in a 929 service error. Diagnostic information 2-171