Code 206000: <location>Infeed: Precharg ing monitoring time expired
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>Infeed: Precharg ing monitoring time expired 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, B_INF, S_INF Reaction: OFF2 (OFF1) Acknowledge: IMMEDIATELY Cause: After the line contactor closes the power unit does not signal the READY state within the monitoring time (p0857). The end of the DC link pre-charging was not able to be completed for one of the following reasons: 1) There is no line supply voltage connected. 2) The line contactor/line side switch has not been closed. 3) The line supply voltage is too low. 4) Line supply voltage incorrectly set (p0210). 5) The pre-charging resistors are overheated as t here were too many pre-charging operations per time unit. 6) The pre-charging resistors are overheated as the DC link capacitance is too high. 7) The pre-charging resistors are overheated because when there is no "ready for operation" (r0863.0) of the infeed unit, power is taken from the DC link. 8) The pre-charging resistors are overheated as the line contactor was closed during the DC link fast discharge through the Braking Module. 9) The DC link has either a ground fault or a short-circuit. 10) The pre-charging circ uit is possibly defective (only for chassis units). See also: p0210, p0857 SINAMICS-Alarms Remedy: In general: - check the line supply voltage at the connecting terminals. - check the line supply voltage setting (p0210). - check the monitoring time and, if required, increase (p0857). - where relevant, observe additional pow er unit messages/signals (e.g. F30027). - the following applies to booksize units: Wait (approx. 8 min.) until the pre-charging resistors have cooled down. The infeed unit must be disconne cted from the supply for this purpose. Re 5): - carefully observe the permissibl e pre-charging frequency (refer to the appropriate Equipment Manual). Re 6): - check the total capacitance of the DC link and if required, correspondingly reduce the maximum permissible DC link capacitance (refer to the appropriate Equipment Manual). Re 7): - interconnect the ready for operation signal of the in feed unit (r0863.0) in the enable logic of the drives connected to this DC link. Re 8): - check the connections of the ex ternal line contactor. The line contactor must be open during the DC link fast discharge. Re 9): - check the DC link regarding ground fault or short-circuit.
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 206000 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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