Error Code U2-40 on Sharp FO-DC550 fax machine.

U2-40

That is a CRUM communication error. The CRUM is a chip that resides on the toner cartridge that keeps track of the toner usage and resets when a new toner is installed. If you replaced the toner recently it may be corrupt. If you got a refurbidhed toner they may have reprogrammed the CRUM incorrectly. Power supply problems often cause this error so check your outlet to make sure it is withinn the proper voltage range and also that it is not on the same circuit as other devices. Get a "real" surge protector designed for office equipment such as a smartpower. Try changing toners and using genuine supplies.