Lexmark T620 Service Manual - Page 150

4069-5XX/7XX Serial Port Service Check Run the "Serial Wrap Test" on page 3-17. Note: The Serial Wrap Test is designed to check the serial port hardware by using a wrap plug (P/N 1329048) and invoking the Serial Post Diagnostic Test. The test helps isolate the printer from the serial cable and host. The test provides failure information on the display for approximately three seconds. If the test indicates a problem, replace the system board. 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 Service Error displays. FRU 1 Developer Drive Assembly 2 Front Harness Cable Action Incorrect operation of the developer drive assembly can cause the printer to display a 929 error code (Toner Sensor). Check the developer drive assembly for correct installation, 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 (J25), check the continuity of the cable. If incorrect, replace the cable. 2-122 Service Manual