Frigidaire refrigerator: SY EF or (5y ef)
This code signals lack of air above the air sensor, meaning there is a sensor problem, or the evaporator fan is not working properly. Most likely, there was a circuit breakdown in the evaporator fan section.
Check the wiring and connections between the fan and control board. Pay attention to 12VDC between the brown and red wires, and variant voltage (the brown and yellow wires). If no problem is found, the evaporator fan may need to be repaired or replaced. It this does not work, check the control board and, if necessary, repair or replace it.
Frigidaire refrigerator: SY CF or SY CE
This error code reports a communication problem when a refrigerator is switched on. Check the wiring and connections between the user interface and control board. If the wiring is ok, there may be a problem in one of these two units.