The Siemens SINAMICS S120 is a modular servo and motion drive built from a Control Unit (CU320-2), a Line Module (Active ALM or Smart SLM) and one or more Motor Modules / axis cards. It runs high-axis-count machining centres, presses, test rigs and material-handling lines where a single control unit coordinates several axes over DRIVE-CLiQ. This architecture is a step beyond the older SIMODRIVE 611U bookshelves already covered on this site, and the failure modes are different: most S120 stops are topology and communication faults, not analog amplifier trips.
When an S120 faults, the CU writes the event to the alarm buffer. Half the “drive will not run” calls we see are a topology mismatch or a DRIVE-CLiQ cable issue, not a dead power stage. This guide covers the Drive-CLiQ, encoder and power-unit codes technicians actually meet, checked against the SINAMICS S120 Commissioning Manual and Diagnostics Manual.
Please check our Siemens servo drive range — including the 6SN1145-1BA02-0CA1 SIMODRIVE axis power module if you are migrating a 611U bookshelf to S120 — if you are sourcing a replacement rather than repairing.
S120 separates two number spaces, and confusing them wastes time:
Fault Manifestations. A01300 reports a topology fault: a configured component is not identifiable, or a DRIVE-CLiQ neighbour returned no valid electronic nameplate. A01301 reports that a component firmware update is required, or the detected device class does not match the project.
Root Causes. A DRIVE-CLiQ cable pulled or not fully seated, a wrong cable (a standard Ethernet patch lead is not a crossover and will not link), a component with mismatched firmware, or a topology project that does not match the physical wiring.
Repair Steps. Open the topology view and compare expected against detected components. Re-seat every DRIVE-CLiQ connector until it clicks; swap a suspected cable for a correct DRIVE-CLiQ lead and re-run topology detection. If A01301 appears, align the component firmware with the CU320-2 release using the Siemens tools, then re-detect. Never commission with the topology forced — a missed component hides a real hardware gap.
Fault Manifestations. F01910 appears when the setpoint telegrams stop — the fieldbus (PROFINET/PROFIBUS) or the DRIVE-CLiQ component message is interrupted. On networked axes the PLC going to STOP or a dropped cable raises it immediately.
Root Causes. A removed or EMC-damaged communication cable, a controller in STOP, a device name or IP mismatch after a switch port change, or a component that lost its 24 V supply on the DRIVE-CLiQ spare pair.
Repair Steps. Confirm the controller is in RUN and the bus cable is intact and separated from power wiring. On PROFINET, verify the device name and IP against the hardware configuration. Where sags are routine, you may re-map F01910 to “no action” for local manual control — but only after confirming this will not create an unsafe condition. Restore the link and re-establish cyclic communication before clearing.
Fault Manifestations. These message numbers (231885 cyclic data transfer error, 231886 error sending DRIVE-CLiQ data, 231887 component fault) appear on Encoder 1 between the Sensor Module and the Control Unit. The axis refuses to run and the fault value r0949 shows the component number and a cause byte.
Root Causes. Loss of 24 V at the encoder, a DRIVE-CLiQ cable fault, a Sensor Module or encoder with a corrupted telegram header, or a firmware mismatch between encoder (r0148) and Control Unit (r0018).
Repair Steps. Check the 24 V supply at the encoder, then carry out a POWER ON of the component. Replace the DRIVE-CLiQ cable if the fault persists, and confirm the encoder firmware matches the CU. Because a faulty hardware component cannot be excluded, swap the encoder or Sensor Module if the telegram errors remain after cabling is ruled out. The DRIVE-CLiQ encoder connection module is the most common single point to replace — see the 6FX2001-8AA05 DRIVE-CLiQ encoder connection module if you need a spare.
Fault Manifestations. Beyond the 231xxx DRIVE-CLiQ messages, S120 raises encoder / motor-feedback faults (the F318xx-class “Encoder 1 fault” family and the 2xxxx message numbers) on zero-pulse, commutation or checksum errors.
Root Causes. A damaged encoder cable, a contaminated or displaced feedback connector, a resolver with a broken supply, or an encoder that lost its absolute reference after a battery event.
Repair Steps. Inspect and re-terminate the feedback cable, check the encoder 24 V and screening, and re-establish the absolute reference where required. For resolver-based feedback, the 1XP8003-10 resolver is a common replacement.
Fault Manifestations. F30004 trips when r0037 (heatsink temperature) crosses the warning threshold; a reading far above ambient while the sink is cool points to a shorted NTC, not real heat.
Root Causes. Failed or sluggish fan, clogged fins, ambient above the limit, pulse frequency (p1800) set high, or a faulty temperature sensor inside the power block.
Repair Steps. Verify fan rotation and the fan board, vacuum the heatsink, and check ambient and load. Drop p1800 if above the rated pulse frequency. Note that r0037 reads -200 °C on unpopulated channels (normal) and +145 °C on a faulted one (a sensor fault) — never raise p0292 or disable p0290 to mask it; replace the power block.
Fault Manifestations. F30021 trips on a detected ground. The fault value r0949 shows which phase (bits 0–2) or a Σ-i amplifier saturation (bit 3); value 0 points at the hardware DC monitor or a brake-resistor short.
Root Causes. A grounded power cable or motor, a damaged converter, a brake-resistor short, or the IGBT self-check failing on a book-size module with a corrupted power-unit EEPROM.
Repair Steps. Megger the power cable and motor, check the brake-resistor wiring and the converter. On book-size Motor Modules, run a power-unit factory reset and confirm r0200 is populated; use simulation mode (p1272 = 1) only for bench testing. Do not raise p0287 to zero to silence it on a live machine.
Fault Manifestations. F30005 trips when the power-unit load (r0036) reaches 100 % for too long.
Root Causes. Sustained current above the rated value, a duty cycle outside limits, or a motor/power-unit rating mismatch.
Repair Steps. Reduce the continuous load, correct the duty cycle, and confirm the motor and power-unit rated currents match. On VECTOR drives, p0294 can be raised within limits.
| Interval | Task | Prevents |
|---|---|---|
| Quarterly | Clean fans and heatsink fins; verify fan rotation | F30004 |
| Every 6–12 months | Inspect DRIVE-CLiQ connectors and seating | A01300, A01301, 231885–231887 |
| Annually | Check encoder cable screening and 24 V supply | Encoder faults, F01910 |
| On commissioning | Save project backup; record topology | All topology faults |
What is the difference between A01300 and F01910?
A01300 is a DRIVE-CLiQ topology fault — a configured component is missing or not identifiable. F01910 is a communication timeout — the setpoint telegrams from the controller stopped. Both stop the axis, but A01300 is about the component list and F01910 is about the live message stream.
Why does 231887 appear right after I changed an encoder?
231887 is an Encoder 1 DRIVE-CLiQ component fault. A new encoder whose firmware (r0148) does not match the Control Unit (r0018) will raise it, as will a telegram-header error. Power-cycle the component, confirm the firmware match, then replace the cable before the encoder.
How do I tell a real F30004 from a failed sensor?
Read r0037. A genuine overheat tracks the cabinet, while a shorted NTC reads around +145 °C while the sink is cool. Do not raise p0292 or disable p0290 to clear it — replace the power block.
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