What the SRVO-027 alarm means
The robot has no valid mastering data. This typically follows BZAL alarms, board replacement, or loading a backup from another controller. This is a routine repair in our workshop for FANUC R-30iA / R-30iB / R-30iB Plus systems, and we normally pin it down during the first site check.
Most common causes
- Mastering data cleared after BZAL/battery failure
- Main board or FROM/SRAM module replaced
- Backup image from a different robot was loaded
Step-by-step field fix
- Perform mastering for all axes (witness-mark or zero-degree mastering)
- Calibrate
- Touch up critical program points if accuracy matters (welding paths, palletizing corners)
- Always back up mastering data (SYSMAST.SV) after completion
How we diagnose calibration alarms on site
FANUC srvo-027 belongs to the battery & mastering family. On FANUC srvo-027 the failing stage is absolute encoders inside alpha-i motors, position memory held by the encoder battery pack on the R-30iB Plus / R-30iB Mate Plus / R-30iA - low battery voltage losing the absolute position memory, which then demands a fresh zero master - two jobs in one. We start reading FANUC srvo-027 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-027 runs: battery pack supply -> absolute position count -> memory held across power-off -> voltage too low loses it -> re-master required.
Once FANUC srvo-027 has lost zero data there are several recovery paths: When zero data is already lost there are several recovery paths with different cost and accuracy. The standard one is a fresh master with fixtures: best accuracy, needs a stop. Some models allow a coarse restore from mechanical datum marks or factory indices, enough to move again while a precision master is scheduled. And if the customer kept earlier calibration data or program backups, a straight restore may apply. We recommend by production urgency: coarse restore to keep running, precision master in the next window.
Field notes on this page cover FANUC srvo-027 (Robot Not Mastered); written by the Henghuan repair team, updated 2026-10-01.
Real Field Case
Machine: FANUC R-2000iC/125L (2020)
Symptom: After the customer replaced a motor, the robot raised SRVO-027 (not mastered) and would not run in auto.
What we did: We mastered the axis with the replaced motor using the calibration pin, re-checked the marks on the other axes, and once aligned wrote and backed up the data.
Result: Auto operation resumed after mastering and we backed the mastering data to USB; about 3.5 hours total.
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Related Battery & Mastering alarms
SRVO-062 — BZAL Alarm (Group / Axis) SRVO-065 — BLAL Alarm - Battery Voltage Low SRVO-075 — Pulse Position Mismatch SRVO-038 — Pulse Mismatch (Group / Axis)Frequently asked questions
QWhat does the FANUC srvo-027 alarm mean?
The robot has no valid mastering data. This typically follows BZAL alarms, board replacement, or loading a backup from another controller. This is a routine repair in our workshop for FANUC R-30iA / R-30iB / R-30iB Plus systems, and we normally pin it down during the first site check. FANUC srvo-027 sits in the battery & mastering family; on our work orders the highest-frequency trigger for this code is "Mastering data cleared after BZAL/battery failure".
QCan I clear a FANUC srvo-027 alarm myself?
Whether FANUC srvo-027 clears on its own depends on the outcome of "Perform mastering for all axes (witness-mark or zero-degree mastering)". Finish the flow with "Always back up mastering data (SYSMAST.SV) after completion" to confirm FANUC srvo-027 - do not skip it. If that step is clean, the second most frequent cause on FANUC srvo-027 is "Main board or FROM/SRAM module replaced". Do not chase takt through a repeating FANUC srvo-027. Left alone, battery & mastering faults tend to graduate from repairable to must-replace.
QWhen you handle FANUC srvo-027, will my programs and frames get lost?
The commonest causes we see on FANUC srvo-027 are "Mastering data cleared after BZAL/battery failure, Main board or FROM/SRAM module replaced, Backup image from a different robot was loaded", so we stock the van against those. For FANUC srvo-027 specifically, we carry the model's battery pack and mastering fixtures; battery changes belong in scheduled maintenance, not in alarm response. For FANUC srvo-027, on battery and mastering alarms we back up programs and points first, master second and verify precision on site. Before we roll, tell us what FANUC srvo-027 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-027 was compiled from actual repair records of the Henghuan Robotics repair team. Alarm notes are our own summary for troubleshooting reference only and may vary with controller and software version — please consult FANUC documentation or contact us if in doubt. Henghuan is an independent service provider, not affiliated with or endorsed by FANUC.