Whenever electricity power suddenly cut-off from the machine this error appears on the screen and I dont know how to restart the machine.

Jamal, September 2008

F21 usually means a motor fault on Bosch washing machine. If it came up after power was interrupted then switch power off at wall switch for a few minutes & turn back on & restart machine from beginning again. If F21 is permanently on then I suggest you call a service person.

Lincoln Appliance NZ, September 2008