Siemens alarm 400202: Access error
SINUMERIK PLC system alarm · Siemens 840D/810D powerline
What it means
The basic program could not access required internal PLC data. Siemens classifies this as a system error rather than a machine-side fault - the alarm gives no parameter because the failure is inside the NCK/PLC runtime environment. If it repeats after a control power cycle, the issue must be escalated to Siemens service with the exact error text.
Likely causes
- Internal system error during PLC data access
- Corrupted PLC runtime state after failed download or power loss
- Defective NCU/CPU memory hardware
Triage note: Official remedy: system error - contact Siemens SINUMERIK Hotline if recurring. Valid for powerline and solutionline.
Need the part urgently?
Send us alarm 400202 with your machine details — typical RFQ turnaround is 24–48h.