F 23 - Washing Machines

The meaning of the code depends on the machine's manufacturer.

On Siemens built machines (Siemens, Electrolux, hotpoints etc.) F23 Means that there is overflow and anti flood device has been activated.
In this case:

Disconnect power.
Remove all water at the base of the machine.
Take off the rear panel, or access the drain pump from front door(depends on model).
Check drain hose height and check hose connected to drain pump.
Connect power back.
If problem does not clear after connecting back, replace pressure switch.

With Wirlpool built machines instead (Whirlpool, Maytag, Kenmore etc.) f23 means there is a communication within the CCU and the MCU.

CCU is the main control module (central control unit), and MCU is the Motor Control Unit. MCU is a sealed module located deep inside the appliance, and connected on one side to the motor, and on the other to the CCU. Testing F23 on a Whirlpool is more difficult and requires a technician. In this case all you can do is disconnecting power, if error does not go away call the service number listed on manual.

Regards.

Ginko