Errorc2557 - Konica Minolta bizhub C250 All-In-One Laser Printer

It is my pleasure to guide you.

Konica Minolta 250 Error C2557 is Toner Density sensor problem

Problem: code C2557 - Abnormally low toner density detected Black TCR Sensor

Sounds like something a technician should take care of. Most of the information I could obtain says that the

Solution: Replaced 4038-R729-00 Hopper Drive Assy (C250 part compatible with C252 )

Good luck and please post back that you are successful, giving thumbs up, or if I can be more helpful.