This is a door open error the control board is seeing the door as open even though it may be closed.
How To Diagnose and Repair Bosch Washer WFMC2100UC/01 Er:01
Unplug the washer and check the plug on the door lock assembly make sure it's pushed in all the way to the door lock.
If the connection looks ok then replace the door lock assembly because it has faulted.
Part# 497255 - Bosch Nexxt Washer Door Lock.