Code A00590: Encoder feedback loss warning
Issue Description & Safety Warning
The Siemens SINAMICS G120 CU240S Drive has triggered a critical Encoder feedback loss warning alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Reaction: NONE Acknowledge: NONE Cause: Signal from Encoder lost; Inverter might have switched to sensorless vector control. Check also alarm value r0947: - r0949 = 0: Encoder signal lost. - r0949 = 5: Encoder not configured in P0400, but required for sensored control (P1300 = 21 or 23). Remedy: Stop inverter and then - Check encoder fitted. If encoder fitted and r0949 = 5, select encoder type via P0400. - If encoder fitted and r0949 = 6, check connections between encoder module and inverter. - If encoder not fitted and r0949 = 5, select SLVC mode (P1300 = 20 or 22). - If encoder not fitted and r0949 = 6, set P0400 = 0. - If encoder fitted, check correct encoder selected (check encoder setup in P0400). - Check connections between encoder and inverter. - Check that encoder not faulty (select P1300 = 0, run at fixed speed, check encoder feedback signal in r0061). - Increase encoder loss threshold in P0492.
Source: SINAMICS G120 Control Units CU240S Faults and Alarms (Edition 05/2007)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINAMICS G120 CU240S Drive Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code A00590 on the SINAMICS G120 CU240S Drive identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 108 Siemens SINAMICS G120 CU240S Drive codes.
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