Did you just replace your color PCUs (photoconductor units)? If so, one of the new units may be defective. Try reinstalling the old units to see if the problem goes away (after resetting the machine). If it does, you can replace the PCUs one by one to see which one is bad.|
If you still get the sc441 even with the old PCUs (or if you don't have them anymore) install a set of new PCUs and that should fix the problem. On the off chance the problem doesn't go away even with new PCUs, contact your local service company because you may have a bad circuit board, motor, or gear.