What the SRVO-251 alarm means

The dynamic brake relay inside the servo amplifier did not switch as commanded. This is one of the faults our repair team handles most often — the cause is usually identifiable within the first on-site inspection.

Most common causes

  • DB relay contact failure (wear/welding)
  • Relay drive circuit fault in the amplifier
Field note: the first item on this list is what we find most often on real machines. Check it before you go deeper.

Step-by-step field fix

  1. This is an internal amplifier fault - swap the amplifier to confirm
  2. Repair or replace the amplifier
  3. Investigate frequent E-stop cycles under load, which stress DB circuits
Safety first: never bypass safety circuits or force contactors closed. If the alarm involves E-stop chains or servo power, and you are not a trained robot technician, contact a professional — wrong moves here can cost you a robot or an injury.

Still stuck? Get an engineer on the phone — right now

Tell us the alarm code, the robot model and what was happening when the alarm came up. Our engineers run these diagnostics every day, and remote diagnosis by phone or video call is free.

Get a Free Remote Diagnosis See Repair Services

Hotline: +86-20-39029800 · WhatsApp: +86-188-1886-2860

Related Amplifier & Hardware alarms

SRVO-057 — FSSB Disconnect SRVO-068 — DTERR - Data Transmission Error SRVO-069 — CRCERR - CRC Error SRVO-071 — SPHAL - Soft Phase Alarm SRVO-072 — PMAL - Pulse Coder Phase Alarm SRVO-073 — CMAL - Pulse Coder Count Error
Other brands: see our KUKA, ABB, Yaskawa and Universal Robots field-fix libraries — or the full 10-brand hub.

Frequently asked questions

QWhat does the FANUC SRVO-251 alarm mean?

The dynamic brake relay inside the servo amplifier did not switch as commanded. In field practice it belongs to the amplifier & hardware family of faults.

QCan I clear a FANUC SRVO-251 alarm myself?

Sometimes. Follow the step-by-step checks on this page — start with the first cause listed, which is what we find most often in the field. If the alarm returns after two attempts, or the fault involves power/safety circuits, stop and call a qualified robot service engineer.

QHow fast can a Henghuan engineer help?

On-site response in the Pearl River Delta within 30 minutes to 3 hours, across mainland China in 1–3 business days, and worldwide within 2–5 business days. Remote diagnosis by phone/WhatsApp/video is available immediately.

Written by the Henghuan Robotics repair team from field service experience. Alarm descriptions are our own summary for troubleshooting reference and may vary by controller version — when in doubt, check your FANUC documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by FANUC.