Siemens SIMATIC Manual page 386

Analog modules
6.9 Analog input module SM 331; AI 8 x RTD; (6ES7331-7PF01-0AB0)
Configuration in RUN
Special considerations must be given if you use the Configuration in RUN function.
SF LED is lit:
Status before re-configuration diagnostics on, SF LEDs lit among others (on CPU, IM or
module), although diagnostics are no longer pending and the module is operating correctly.
Solution:
● Only change the configuration when no diagnostics are pending for the module or
● Pulling and plugging the module.
386
S7-300 Module data
Manual, 06/2017, A5E00105505-AJ