Siemens alarm F31120: Encoder 1: Power supply voltage fault
SINAMICS S120 encoder fault (Sensor Module / DRIVE-CLiQ encoder) · SINAMICS S120
What it means
A supply problem was detected feeding encoder 1: undervoltage on the sense line, overcurrent on the encoder power or resolver-excitation lines, overloaded 24 V through the Power Module, or overcurrent/overvoltage/hardware fault at the converter's EnDat connection. The manual explicitly warns that interchanging encoder cables 6FX2002-2EQ00-... and 6FX2002-2CH00-... reverses operating-voltage pins and can destroy the encoder.
Likely causes
- wrong or swapped encoder power/signal cable type
- short-circuit or overload in the encoder supply path
- damaged Sense/Sensor Module supply circuitry
- EnDat connection hardware fault in the converter
Triage note: Decode r0949 bit 0-7 to localize; bits 6/7 point to the converter's EnDat driver hardware.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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6FX2002-2EQ00-… / 6FX2002-2CH00-… (verify correct pairing!)
cable · Common cause
Need the part urgently?
Send us alarm F31120 with your machine details — typical RFQ turnaround is 24–48h.