What the SRVO-231 alarm means

The 0V side of the dual-channel emergency stop chain is abnormal. Same family as SRVO-230, opposite rail. We fix this FANUC R-30iA / R-30iB / R-30iB Plus fault almost daily, and one round of on-site checks usually confirms what is going on.

Most common causes

  • Same as SRVO-230: single-channel wiring, failed contacts, broken wiring on the 0V rail
  • E-stop board failure
  • Short between chain 2 and ground
Field note: We have tallied real cases: the first cause tops the list, so start your diagnosis there.

Step-by-step field fix

  1. Follow the SRVO-230 procedure
  2. Pay extra attention to shorts to cabinet ground on the 0V rail
  3. Swap E-stop board with a known-good unit if wiring checks out
Safety first: For FANUC srvo-231, this alarm is the safety circuit itself: jumpering a door switch or forcing a contactor removes the protection entirely - no protective action when something happens, and no defensible account of responsibility. What you can check yourself first is Follow the SRVO-230 procedure; the e-stop chain and safety circuit handling is not a DIY job.

How we diagnose safety-chain faults on site

FANUC srvo-231 belongs to the safety chain & e-stop family. On FANUC srvo-231 the failing stage is Dual Check Safety (e-stop board plus dual-channel safety circuit) on the R-30iB Plus / R-30iB Mate Plus / R-30iA - continuity of one series loop: e-stop buttons, door switches, light curtains, safety relays and the enabling device. We start reading FANUC srvo-231 at the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code.

The chain involved in FANUC srvo-231 runs: e-stop / door / curtain -> safety relay (dual channel) -> controller safety input -> motor-off and brake apply.

On FANUC srvo-231 the field usually reports Same as SRVO-230: single-channel wiring, failed contacts, broken wiring on the 0V rail, but the check that matters is not continuity: The point of a safety loop is not whether it conducts but whether both channels conduct together. The relay compares channels; if one opens tens of milliseconds early it latches as a channel fault. The commonest causes are plain: oxidised door-switch contacts raising contact resistance, or one loose terminal. We measure segment by segment - pendant e-stop, panel e-stop, external e-stop, safety door - and lock onto whichever segment reads differently on the two channels.

Field notes on this page cover FANUC srvo-231 (Chain 2 (0V) Abnormal); written by the Henghuan repair team, updated 2026-10-01.

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Related Safety Chain & E-Stop alarms

SRVO-105 — Door Open or E.Stop SRVO-201 — Panel E-Stop SRVO-202 — TP E-Stop SRVO-204 — External E-Stop (SVEMG Abnormal) SRVO-230 — Chain 1 (+24V) Abnormal SRVO-232 — NTED Input Abnormal
Same family: this code belongs to the Safety chain & e-stop alarms family - the page collects all Safety chain & e-stop-family codes we have handled, with the common inspection order and spares.
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-231 alarm mean?

The 0V side of the dual-channel emergency stop chain is abnormal. Same family as SRVO-230, opposite rail. We fix this FANUC R-30iA / R-30iB / R-30iB Plus fault almost daily, and one round of on-site checks usually confirms what is going on. FANUC srvo-231 sits in the safety chain & e-stop family; on our work orders the highest-frequency trigger for this code is "Same as SRVO-230: single-channel wiring, failed contacts, broken wiring on the 0V rail".

QCan I clear a FANUC srvo-231 alarm myself?

Whether FANUC srvo-231 clears on its own depends on the outcome of "Follow the SRVO-230 procedure". Finish the flow with "Swap E-stop board with a known-good unit if wiring checks out" to confirm FANUC srvo-231 - do not skip it. If that step is clean, the second most frequent cause on FANUC srvo-231 is "E-stop board failure". Do not chase takt through a repeating FANUC srvo-231. Left alone, safety chain & e-stop faults tend to graduate from repairable to must-replace.

QA safety-chain fault like FANUC srvo-231 stops the line - how fast can you be here?

The commonest causes we see on FANUC srvo-231 are "Same as SRVO-230: single-channel wiring, failed contacts, broken wiring on the 0V rail, E-stop board failure, Short between chain 2 and ground", so we stock the van against those. For FANUC srvo-231 specifically, we stock along the loop: safety relays, common door switches, e-stop buttons, light-curtain pairs and terminal blocks. For FANUC srvo-231, a safety-chain fault stops the whole line, so we rank it top priority and pre-triage by phone: door switch, e-stop or relay. Before we roll, tell us what FANUC srvo-231 shows on the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code and what the machine was doing - phone or video triage is free.

This page on FANUC srvo-231 is based on the field experience of the Henghuan Robotics repair team. Alarm explanations are our own summary for troubleshooting reference and may differ across controller and software versions — if unsure, verify against FANUC documentation or reach out to us. Henghuan is an independent service provider with no affiliation or endorsement by FANUC.