I have a Sharp AR-163 copier and it flashs U2 40.

U2 40 is a CRUM error. This basically means you need to try a different toner cartridge.

Most commonly a toner cartridge issue. First try removing then reinstalling the toner cartridge and power off the machine. If this does not solve your issue then reset the error using the following:
Press these keys in sequence: #, interrupt, clear, interrupt. (screen should say service mode), enter 16, press print, it will ask are you sure? press yes.
This will reset the code so you can see if the code comes back
If it does then you have to change the toner, it has a defective crum (counter chip) on the back of it