Siemens Simatic S7-1500R System Manual page 64

Diagnostics
System state, operating states and error displays after primary-backup switchover:
● Redundant system → RUN-Solo system state
● Primary CPU → RUN operating state
– MAINT LED → yellow light: The R/H system is not in the RUN-Redundant system
● Backup CPU → failed
Note
To get detailed diagnostics information, evaluate the diagnostics buffer.
Solution
Replace the defective CPU. You can find additional information on the procedure in the
section Replacing defective R/H CPUs (Page 260).
S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA
state. No partner CPU has been found in the redundant system.
Application planning
3.4 Redundancy scenarios
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