The printer dsiplays a 121.xx Service Fuser Error (except for 121.02. 121.16, 121.41 and 126.01 service errors, please follow troubleshooting steps in this article.
Make sure that the printer is plugged directly into a wall outlet.
Power off the printer, wait for a few seconds and power the printer back on.
LEGACY ID: SO7255
Here are steps to troubleshoot an intermittent 121.16 Fuser Error message on a Lexmark CSx10, CXx10, C2132, or XC2132.
"42" or "42.xx" Toner Cartridge Mismatch Error