Key takeaways
When a Sinumerik control stops with an alarm, the number range tells you which subsystem raised it and the alarm text tells you where to look. This guide is for maintenance technicians and plant engineers who need to classify a Sinumerik alarm fast, run sensible first checks, and reset it safely on 810D, 840D and Sinumerik ONE machines.
Siemens groups alarms by source subsystem, and the number range is the key. Reading the range first saves you from chasing the wrong cabinet.
| Number range | Source | Typical examples | Where to look first |
|---|---|---|---|
| 10000 to 19999 | Channel alarms | 10910 contour errors, program syntax stops | Part program, tool data, kinematics |
| 20000 to 29999 | Axis and spindle alarms, including the measuring system | 25000 and 25001 encoder hardware faults, 25020 zero mark monitoring, 25050 contour (following error) monitoring, 26000 clamping monitoring | Encoder, feedback cable, connectors and shielding first, then mechanics, load and servo settings |
| 2xxxxx on 840D sl and Sinumerik ONE; 300xxx on 840D and 810D with SIMODRIVE 611D | Drive system (axis and spindle drives) | 207900 motor blocked, 230001 power unit overcurrent, 300500 system error on 611D, enable and DC bus problems | Drive modules, motor cables, enable chain, infeed |
| 500000 to 899999, most often 700000+ | PLC / machine builder alarms | Lubrication, guard, magazine, coolant messages | The machine builder's documentation, not Siemens manuals |
One structural point that confuses new technicians: two documents describe your machine. Siemens documents the NCK, drive and encoder alarms. The machine builder documents everything in the 700000+ range, because those alarms come from the builder's own PLC program. If the alarm text mentions a guard, a magazine, a lubrication unit or a conveyor, it is almost always a builder alarm.
A Sinumerik alarm line carries more than the number. Note all of it before resetting, because the alarm text disappears with the reset and the parameters are the diagnostic gold.
Write the full line down or photograph the screen, then check the history. A drive alarm that always follows an encoder alarm is a symptom, not the disease.
On 840D sl and Sinumerik ONE the drive system reports SINAMICS messages numbered 2xxxxx (for example 207900 motor blocked or 230001 power unit overcurrent); older 840D and 810D machines with SIMODRIVE 611D drives use 300xxx. Either way the range covers infeed, drive modules, motor cables and motors. In practice the most frequent culprits are not burned electronics but the enable chain: emergency stop circuits, guard door switches, drive enable terminals and contactors that feed the infeed module. If several axes drop out at once, suspect the common enables and the infeed before any individual drive.
Sensible first checks, in order:
Safety note: drive cabinets store energy in the DC bus capacitors well after power off. Lock out, wait the discharge time stated on the module, and verify with a meter before touching power terminals. Never bridge door switches or enable signals to test, and support vertical axes mechanically before releasing any brake.
The same discipline applies on other controls; the Fanuc equivalent readiness fault is covered in our Fanuc alarm 401 (VRDY OFF) guide .
Alarms in the 25000 range mean the control does not trust the position feedback. Typical texts mention encoder hardware, signal amplitude or zero-mark monitoring. The physical causes are mundane and mechanical far more often than electronic:
Distinguishing a bad encoder from a bad cable or drive input is a swap-and-observe exercise. Our guide on encoder failure symptoms and testing walks through the checks in detail, and they map one-to-one onto Sinumerik 25xxx alarms.
Two examples show how the NCK range behaves. Alarm 10910 and its neighbors report contour and velocity violations: the programmed path demands more than the axis dynamics allow. The fix lives in the program or the tool data, not in the cabinet. Program-syntax stops similarly point at the part program: a corrupt transfer, a missing tool offset, or an edit made at the machine.
The practical rule: if the alarm is in the 10000 to 19999 channel range and the machine ran fine yesterday, ask what changed in the program or offsets before opening any door. Interview the operator, check the last edits, and compare against a known-good version of the program.
These alarms are written by whoever built the machine around the Siemens control. Lubrication pressure, chip conveyor overload, tool magazine position, guard locks and coolant level all report here. The Siemens Diagnostics Manual cannot help you; the machine builder's electrical drawings and alarm list can.
If the builder documentation is missing, the underlying logic often reads like the faults covered in our Siemens S7 PLC SF fault LED troubleshooting guide: an input that never arrived, a sensor that failed, or a timer that expired waiting for a confirmation switch. Trace the alarm number to the PLC message text, then to the sensor or actuator it monitors.
Sinumerik distinguishes alarm classes by how they clear. Some clear with the Cancel/Alarm Cancel key, some need Reset on the machine control panel, and drive faults frequently require a full control power cycle before the drive re-enables. The alarm help text states the clearing condition.
Two rules keep resets from making things worse. First, fix or at least understand the cause before resetting; repeatedly resetting into an overcurrent can destroy a marginal drive module. Second, after any encoder or drive work on an absolute-referenced axis, verify the reference position against a physical datum before running a program. An axis that lost its bearings will happily execute a perfect crash.
A Sinumerik machine that throws the same 25xxx alarm every few weeks has a failing cable or connector, and what gets it an engineering fix instead of a shrug is a record.
Log every alarm stop as a downtime event with the alarm number as the cause code, and track MTBF per machine and per alarm family.
Chronic offenders then surface in the data with their real cost attached, which is what justifies replacing a cable track or an encoder on schedule instead of at 2 a.m.
That fault history also makes the repair itself faster: the technician who sees that the last three stops on this axis were all signal-amplitude alarms goes straight to the connector with contact cleaner and a crimp kit. This measurement-first habit is the core of OEE for manufacturing: availability losses only shrink when they are counted honestly.
Manual downtime logs miss short stops, and operators rarely type alarm numbers into a spreadsheet at the end of a shift.
Fabrico is a cloud-based MES and OEE platform for manufacturers, with maintenance management (CMMS) built in: it records stops and micro-stops that manual logs and sensors miss, and maintenance work orders take each loss from detection to fix, so every Sinumerik alarm stop becomes a counted, categorized event with a work order trail.
If your alarm history lives in operators' memories today, book a Fabrico demo and see what verified downtime data changes.
Because 840D sl, 828D and Sinumerik ONE machines run Sinamics drives underneath, the drive-side fault families are covered in our Sinamics drive fault codes guide.
Look up a SINAMICS message. On 840D sl and Sinumerik ONE, drive messages appear on the control as a six digit number starting with 2. To find the full description in the SINAMICS S120/S150 List Manual, replace that leading 2 with the letter F for a fault or A for an alarm: alarm 207016 is fault F07016, and alarm 201330 is A01330.
Read the clearing condition. Each NC alarm's help text names how it clears, for example with the Delete key or NC START, with the RESET key, or only by switching the control off and on. SINAMICS messages come in two kinds: faults need the cause removed and then an acknowledgment, while alarms reset themselves once the cause is gone. If a drive message will not acknowledge, check its acknowledgment type in the manual before cycling power.
They come from the drive system: infeed, drive modules, motor cables, motors and their enable signals. Check emergency stops, guard doors, DC bus status and motor connectors first, then the specific drive and motor. The exact fine code is documented in the Diagnostics Manual for your control generation.
Damaged or contaminated feedback cables, coolant in connectors, degraded shielding, or a failing encoder. Intermittent alarms that appear under load or vibration usually point at cables and connectors rather than the encoder itself.
Alarms from 500000 to 899999, most often in the 700000 user area, are created by the machine builder's PLC program, not by Siemens. Their meanings are specific to your machine and are documented in the machine builder's alarm list and electrical drawings.
Depends on the alarm class: some clear with the Cancel key, some with Reset on the machine control panel, and many drive alarms only clear with a full power cycle. The alarm help text names the clearing condition. Always address the cause first, and verify axis reference positions after encoder or drive work.
The range structure is similar but exact numbers, fine codes and texts differ between generations and drive families. Confirm the meaning in the Diagnostics Manual matching your control and drive system before replacing hardware.
Stop chasing this fault by hand. Fabrico logs each stop against the machine's history, so a repeating fault shows up before it becomes a hard line stop, and the team can open a prioritized work order with the stop itself captured on video wherever a camera covers the line.
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