The U2-40 error code mostly commonly appears on Sharp copiers when a new toner cartridge is installed. The error code is produced by a faulty chip on the rear of the toner cartridge.
While many toner cartridge refill kits claim to be the genuine article, often their chips are slightly different from the manufacturer's toner cartridges. This is the most common cause of the U2-40 error on Sharp copiers.
Sometimes, the chip from the previous toner cartridge can be swapped with the faulty chip of the newer cartridge. This chip is called the CRUM Chip. While this is not an ideal solution, it can work in a pinch to produce a functioning toner cartridge.
The U2-40 error can be cleared rather simply. Press P, *, C, * to enter the service simulation. Enter 16 using the keypad, then the Copy Start button. Press Execute on the screen. Replace the toner cartridge if the error persists.