If you get an error code SC551 on your Ricoh copy machine, it means that you have some problem with fuser unit. You can try to reset this error code buth I reccomend you to do this only once.
On the keyboard panel, type 8 0 6 1 8 2 then hold down “C” key and wait to change the display. Turn off the machine and turn it on. If the code reappears call your service provider and inform them of the code that is displaying on the operation panel.
If you are an tehnician man, it means that end thermistor is open (replace it) or maybe the upper heat roller is damaged.