Robotics in Manufacturing

Troubleshooting workflows

Clearing a FANUC SRVO Servo Alarm Safely

This guide is for maintenance technicians who need to investigate and clear an SRVO servo alarm on a FANUC robot without masking a developing mechanical or electrical fault. You'll read the exact code, subcode, and group/axis off the alarm screen, look up its documented Cause and Remedy, do the physical checks that Remedy calls for, then verify at reduced speed before returning to production. The whole point is safe diagnosis, so a chain, brake, e-stop, servo-power, or abnormal-motion fault gets fixed or escalated, never reset-and-run.

Intermediate~45 min17 steps
  1. Step 1.

    Secure the cell before you touch anything

    A SERVO-severity alarm turns off power to the servo system and stops the robot immediately, but the cause may still be live. Clear all other people from the work envelope and keep the cell secured while you diagnose. Only a qualified technician should be inside operating the pendant.

  2. Step 2.

    Read the exact code, subcode, and group/axis

    The first and second lines of the teach pendant show the active alarm; the FAULT lamp on the pendant or operator's panel confirms an alarm is present. Note the full code such as SRVO-050, and read the group and axis from the message, since most SRVO messages carry (G:x A:x) or (Group:x Axis:x). The number in the brackets is the group number and the axis number in the group, which tells you which joint to inspect.

  3. Step 3.

    Open the alarm history and detail screen

    Select the alarm history screen [4 ALARM] to see the sequence of events, then press F5 DETAIL to read the alarm detail code, severity, and generation date and time. A companion code often names the real cause, for example a collision alarm that arrives with related faults. Note that a WARN alarm is not recorded in history when system variable $ER_NOHIS is 1.

  4. Step 4.

    Read the severity so you know what stopped

    The severity tells you whether the program paused, the robot decelerated or stopped immediately, and whether servo power dropped. A SERVO-severity alarm pauses or aborts the program and turns off servo power to stop the robot at once, and the manual states its most common cause is hardware failure. Treat SERVO and SYSTEM severities as real faults to investigate, not banners to clear.

  5. Step 5.

    Look up the documented Cause and Remedy

    Find the exact code in the Alarm Code List (B-83284EN-1) and read its Cause and Remedy in full before acting. The pendant banner names the fault, but the manual lists the probable causes and the ordered checks. Do only what the Remedy supports for that code, and do not invent steps it does not describe.

  6. Step 6.

    Classify the alarm so you check the right things

    SRVO codes fall into distinct subclasses that need different checks. An encoder or battery alarm like SRVO-062 BZAL or SRVO-063 RCAL points at the Pulsecoder, its backup battery, or its cabling; a collision or overload like SRVO-050 or SRVO-046 OVC points at mechanics, payload, or motion; a servo-ready or e-stop fault like SRVO-021 SRDY off or SRVO-002 points at amplifier, wiring, or a tripped safety input. Identify the subclass first, then work its specific Remedy.

  7. Step 7.

    Handle a safety-circuit alarm by clearing the real condition

    For SRVO-002 Teach pendant E-stop, the Remedy is to twist the pendant EMERGENCY STOP button clockwise to release it, then press [RESET]; the operator-panel e-stop SRVO-001 is released the same way. Do not defeat, jumper, or mask an e-stop, fence, deadman, or other chain input to make it clear. If such an alarm cannot be reset after the physical cause is corrected, route it to a qualified technician per the manual, which points to the emergency-stop board or teach pendant.

  8. Step 8.

    Investigate a collision or overload alarm at the mechanics

    SRVO-050 Collision Detect means the servo software estimated an excessively large disturbance torque; documented causes include a real collision or external force, overload or heavy acceleration, increased friction from low temperature, low supply voltage, or brake, amplifier, motor, cable, reducer, or balancer failure. Check whether the robot actually collided, then verify the payload mass, center of gravity, and inertia are set correctly and that the applied load is within rating. The allowable disturbance threshold can be viewed on the Disturbance Torque screen [4 STATUS / Axis / DISTURB], so do not raise it to hide a real fault.

  9. Step 9.

    Investigate an overcurrent alarm at load and duty

    SRVO-046 OVC means the internally calculated RMS current exceeded the permissible value, and the alarm exists to protect the motor and amplifier from thermal damage. Documented causes include overload, increased friction from continuous very slow motion, external force, a disconnected brake cable, low voltage, or brake, amplifier, motor, or cable failure. Check duty and applied load against the rating and confirm the brake cable and connectors are seated before considering component replacement.

  10. Step 10.

    Investigate a battery or encoder alarm at the Pulsecoder

    SRVO-062 BZAL is issued when the Pulsecoder absolute-position backup battery is empty or not connected, and the manual notes that if it appears right after a battery change the internal battery cable may have come loose. The Remedy is to replace the battery in the battery box of the robot base, check the internal cable that feeds power from the battery to the Pulsecoder for a disconnection or ground fault, and replace the motor if needed. SRVO-063 RCAL flags an abnormal Pulsecoder rotation counter and calls for checking the controller-to-robot ground connection first; the low-battery warning SRVO-065 BLAL asks you to replace the battery promptly, with power on, before position data is lost.

  11. Step 11.

    Investigate a servo-ready alarm at the amplifier and setup

    SRVO-021 SRDY off means the ready signal from the servo amplifier for that group and axis turned off. The Remedy starts by checking the alarm history for other alarms that occurred together, since those usually name the real cause, then checking auxiliary-axis and machine-lock settings before suspecting a hardware part. Follow that order and refer amplifier-level hardware faults to the Controller Maintenance Manual and a qualified technician.

  12. Step 12.

    Do the physical checks the Remedy calls for, under lockout

    When the Remedy asks you to inspect cabling, connectors, the battery, or mechanics, apply lockout/tagout before opening any cabinet or dress pack. Check that motor power and brake cables and connectors are seated and not cross-connected to another motor, and that shielding is grounded, exactly as the code's Remedy describes. Use a multimeter only for the continuity or voltage checks the manual specifies, and replace parts only when the Remedy directs it.

  13. Step 13.

    Understand how RESET and FAULT RESET behave

    After you eliminate the cause, press the RESET key on the teach pendant or operator's panel; the active alarm on the first two lines disappears, servo power is restored if it was off, and resetting usually re-enables the robot. A FAULT RESET input from a peripheral device clears faults the same way. RESET clears the alarm state, it does not fix the underlying fault, so never rely on repeated resets to keep running.

  14. Step 14.

    Know when an alarm will not clear until you act

    Many servo alarms carry the note that you must cycle power to release them, for example SRVO-046 OVC and SRVO-043 DCAL. Pulsecoder alarms such as SRVO-062 and SRVO-063 require a PULSE RESET and then a power cycle, and if the alarm returns the cause is still present and must be removed first. If a code documents that it cannot be reset, treat that as a real hardware condition rather than forcing it clear.

  15. Step 15.

    Run PULSE RESET and re-master if a Pulsecoder alarm required it

    To clear SRVO-062 or SRVO-063 after fixing the cause, do PULSE RESET on MENU > SYSTEM > F1 [TYPE] > Master/Cal, then press F3 RES_PCA, and cycle power. The controller then posts SRVO-075 Pulse not established, which you clear by resetting and jogging the affected axis about one motor revolution until it stops recurring. Mastering is then required before the axis reports accurate position, so follow the model's mastering procedure and verify against the witness marks.

  16. Step 16.

    Verify at T1 low speed before AUTO

    With the three-mode switch in T1, tool-center-point and flange speeds are limited to 250 mm/s or slower, so run the affected motion from the teach pendant at reduced speed first. Confirm the axis moves smoothly and the alarm does not return before switching to AUTO and full production speed. Keep the cell clear during this test.

  17. Step 17.

    Watch for recurrence and escalate a repeating fault

    Monitor the axis over the following cycles, since a repeating SRVO alarm usually points to a developing hardware fault rather than a one-time event. A recurring SRVO-050 after payload and motion are verified suggests a mechanical, brake, or amplifier problem; a returning SRVO-062 after a fresh battery points at the internal battery cable or the Pulsecoder; a persistent SRVO-021 points at amplifier or setup faults. If the cause is not resolved, treat it as a hardware investigation and route brake, chain, e-stop, servo-power, or abnormal-motion faults to a qualified technician.

Common questions

How long does Clearing a FANUC SRVO Servo Alarm Safely take?
Clearing a FANUC SRVO Servo Alarm Safely is rated Intermediate and takes about 45 minutes across 17 steps.
What tools do I need?
You will need Teach pendant with alarm and alarm history screens, FANUC Alarm Code List (B 83284EN 1) for the SRVO family, Controller and mechanical unit maintenance manuals for the specific model, Multimeter for motor power, brake, and cable continuity checks if the Remedy calls for it, Replacement Pulsecoder backup battery if a battery alarm is indicated.
What should I do before starting?
The robot is stopped with the SRVO alarm active and the cell is secured.. The technician is trained to read the alarm and alarm-history screens and to work inside the controller cabinet.. The exact SRVO code, its detail code, and the group and axis number have been noted.. Lockout/tagout and site access controls are ready before any cabinet or dress pack is opened.. You have the Alarm Code List so you can read the documented Cause and Remedy for the specific code..
What is the first step?
Secure the cell before you touch anything. A SERVO-severity alarm turns off power to the servo system and stops the robot immediately, but the cause may still be live. Clear all other people from the work envelope and keep the cell secured while you diagnose. Only a qualified technician should be inside operating the pendant.

Attribution

Procedure steps on this page are checked against the site's editorial safety rules and manufacturer-manual sourcing standards.

Last reviewed: 2026-07-21.

Edited by Mike Ramsey / Reliable Media.Editorial process