Code 206500: <location>Infeed: Line synchronization not possible
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>Infeed: Line synchronization not possible 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
Message value: Drive object: A_INF, S_INF Reaction: OFF2 (OFF1) Acknowledge: IMMEDIATELY (POWER ON) Cause: The line synchronization is not possi ble within the monitoring time. The infeed was re-synchronized to the line suppl y because it was interrupted due to a line frequency that was determined to be either too low or too high. After 20 attempts, synchronization - and therefore also the power-on operation - were interrupted. Remedy: - check the parameterized line frequency and if required change (p0211). - check the setting of the threshold values (p0284, p0285). - check the line supply. - when a Voltage Sensing Module ( VSM) is used: check the line supply to the VSM terminals X521 or X522. - check the line supply quality. See also: p0211 (Rated line freq), p0284 (Line s upply frequency exceeded, alarm threshold), p0285 (Line supply frequency undershot, alarm threshold)
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 206500 on the SINUMERIK 840D CNC 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: 4014 Siemens SINUMERIK 840D CNC codes.
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