Interrupts, diagnostics, error messages and system events
11.1 Status and error display of the CPU
CPU 1516pro-2 PN (6ES7516-2PN00-0AB0)
116 Operating Instructions, 11/2019, A5E35873416-AC
Meaning of the RUN/STOP, ERROR and MAINTENANCE LEDs
The CPU 1516pro-2 PN has three LEDs for displaying the current operating state and
diagnostic status. The following table shows the meaning of the various combinations of
colors of the RUN/STOP, ERROR and MAINTENANCE LEDs.
Table 11- 1 Meaning of the LEDs
Missing or insufficient power supply on the CPU.
LED off
LED off
An error has occurred.
CPU is in RUN mode.
LED lit green
LED off
A diagnostics event is pending.
LED lit green
LED off
LED lit yellow
Maintenance demanded for the plant.
The affected hardware must be
checked/exchanged within a short period.
LED lit green
LED off
Bad configuration
LED lit green
LED off
An error has occurred.
LED lit yellow
LED off
LED lit yellow
LED off
Firmware update successfully completed.
CPU is in STOP mode.
LED lit yellow
LED flashes red
LED flashes yellow
The program on the SIMATIC memory card is
LED flashes yellow
LED off
LED off
CPU is performing internal activities during STOP,
Download of the user program from the SIMATIC
LED flashes
LED off
LED off
Startup (transition from RUN → STOP)
LED flashes
LED flashes red
LED flashes yellow
Test of LEDs during startup, inserting a module.