6ES7522-1BL01-0AB0 Siemens — Digital output module — output not activating
At a glance
- Severity
- DEGRADED
- Domain
- PLC
- Reference standard
- IEC 61131-2
- Product / context
- DQ 32x24VDC/0.5A HF — S7-1500
What it means
A digital output channel on the PLC does not switch: the module relay or transistor does not activate. The connected actuator (contactor, solenoid valve, indicator light) does not receive the command. The output status LED on the module may be on (downstream problem) or off (program or module problem).
Probable causes
- Output protection fuse blown (modules with integrated fuse per channel group).
- Module relay contact worn or welded (for relay modules after millions of cycles).
- External output power supply (L+) missing or interrupted.
- PLC program not activating the output bit due to interlock logic or safety condition.
Where to start
Observe the output status LED on the PLC module. Is the channel LED on when the program commands the output?
Full guided diagnosis in the app
The diagnostic tree for this fault has 7 guided steps with measurements, checks and resolutions. You'll find it in ElectraIQ, one of the four IndexOS apps: free, works offline.
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The same fault on other brands
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