Siemens SIMATIC ET 200SP Manual page 17

Meaning of the DIAG LED display on the communication module
The CM DP communication module has an LED for monitoring the diagnostics.
DIAG LED
Table 5- 1
DIAG LED
Additional information
You can find more information on diagnostics in the Diagnostics function manual
(http://support.automation.siemens.com/WW/view/de/59192926/0/en) for diagnostic options
that are available for SIMATIC systems S7-1500, ET 200MP, ET 200SP and ET 200AL.
Communication module CM DP (6ES7545-5DA00-0AB0)
Manual, 12/2014, A5E33619758-AB
DIAG LED fault display
Meaning
Module parameters not assigned
Flashes
Module parameters assigned and no diagnostics
On
Diagnostics of subordinate modules (as of firmware version V1.7)
Flashes
Diagnostics, error and system alarms
5.1 Status and error displays
17