The technician is dispatched to a multi-function device that users print and copy from all day. The technician is told pages that are copied all have a line on them on the left hand side of the…

Replacing the toner cartridge addresses print-path issues - since the test page showed no line, the toner is not the cause and replacement would be unnecessary.

Printing from another workstation tests the print path again, which already produced clean output - this does not help isolate the copy-specific problem.

Closing the ticket without investigating the copy function is inappropriate - the user reported a real, reproducible problem specific to copying that has not yet been diagnosed.

By copying a known-clean printed page, the technician can confirm whether the line is produced by the scanner assembly (copy/scan path) and not the print path. This is standard multifunction device isolation methodology - the test page eliminates the print engine as the source, so copying a document tests the scanner flatbed, document feeder, or scan lamp, which is where a persistent vertical line in copy output originates.