Siemens SIMATIC S7-1500 Manual page 36

Interrupts, error messages and diagnostics and system alarms
5.1 Status and error display of the CPU
Meaning of the RUN/STOP, ERROR and MAINT LEDs
The CPU 1518T-4 PN/DP has three LEDs for displaying the current operating state and
diagnostic status. The following table shows the meaning of the various combinations of
colors for the RUN/STOP, ERROR and MAINT LEDs.
Table 5-1 Meaning of the LEDs
RUN/STOP LED
LED off
LED off
LED lit green
LED lit green
LED lit green
LED lit yellow
LED lit yellow
LED lit yellow
LED lit yellow
LED flashes yellow
LED flashes
yellow/green
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ERROR LED
LED off
LED flashes red
LED off
LED off LED lit yellow
LED off
LED flashes yellow
LED flashes red
LED off
LED flashes yellow
LED off
LED flashes red LED flashes yellow
LED off
LED off
MAINT LED
Missing or insufficient power supply on the CPU.
LED off
An error has occurred.
LED off
CPU is in RUN mode.
LED off
Maintenance demanded for the plant.
You need to check/replace the affected hardware
within a short period of time.
Active Force job
OPC UA server of the CPU expects initial trust lists
and CRLs via GDS Push function.
Bad configuration
A diagnostics event is pending.
LED off
Firmware update using SIMATIC memory card suc­
cessfully completed.
CPU is in STOP mode.
LED off
CPU runs a program with active breakpoints. The
program is at a breakpoint.
The program on the SIMATIC memory card is caus­
ing an error.
Firmware update using SIMATIC memory card has
failed.
The CPU has detected an error state. Additional
information is available via the CPU diagnostic buf­
fer.
CPU is performing internal activities during STOP,
LED off
e.g. startup after STOP.
Download of the user program from the SIMATIC
memory card
CPU carries out a program with active breakpoint.
The program is presently moving from one break­
point to another.
Firmware update is being performed.
Startup (transition from STOP → RUN)
LED off
Meaning
CPU 1518T-4 PN/DP (6ES7518-4TP00-0AB0)
Equipment Manual, 11/2022, A5E50479758-AB