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That axis's digital servo system has detected an internal fault and reported it to the CNC. It is an umbrella alarm: underneath there is a detail sub-code that says what actually happened, and without it there is no diagnosis. It usually ends up being a maintenance job, but there are checks you can do first that save a call-out.
For reference only: alarms change with the manufacturer, the control and the machine PLC. Check the full code in the official manual before doing anything. Legal notice.
Practically always if it returns after reset, because it usually requires drive/axis diagnosis.
Reset just to confirm if it was temporary; If it comes back, stop.
Choose the manual matching your control series, software version and machine builder. A support portal is a starting point; it does not establish applicability to every model.
In a Fanuc digital servo, the CNC and the amplifier split the work: the control calculates commanded position and the amplifier closes the fast velocity and current loops while watching its own condition. The amplifier and the control's servo software run self-diagnostics continuously: instantaneous overcurrent in the power stage, DC bus voltage out of range, inconsistent encoder feedback, overflow in some internal loop calculation, a mismatch between the loaded parameters and the hardware actually connected. When any of those self-checks fails, it does not stop to explain: it kills motor excitation and reports a digital servo system alarm for that axis to the CNC, with a sub-code or detail bits on the diagnostic screen that are what tell one case from another. That is why guessing from the alarm text is useless: SV0414 with an overcurrent detail points at the motor, the cable or the power stage; with an undervoltage detail it points at the supply or at very aggressive braking feeding energy back; with a feedback detail it points at the pulse coder and its wiring. The practical catch is that a chafed power cable or a loose shield can produce any of those details intermittently, and that intermittency is the hard part.
In order, from the fastest and cheapest check to the most expensive.
01Write down the axis, the full number and the sub-code
SV0414 on its own is not enough: you need the axis and the detail shown on the servo diagnostic screen. On many series that information sits in the diagnostic numbers around the 200 range, but the exact location changes between series, so look it up in your control's maintenance manual as servo alarm diagnostics. That figure is the first thing the service engineer will ask you for.
02Pay attention to when it appears
At power-up with nothing moving points at supply, parameters or hardware. When motion starts, at power or feedback. Only during hard acceleration or braking, at overcurrent or bus voltage. Only after hours of running, at temperature or a contact that degrades as it warms up. This information is worth as much as the sub-code.
03Repeat the full power-down cycle
Power down by the procedure, wait as long as the builder specifies and switch back on. If the fault was transient it goes away. If it comes back with the machine at rest and nothing having moved, it is a hard fault and there is no point resetting again: every retry with a hard power fault is added risk.
04Reconstruct what was touched beforehand
A motor or amplifier change, parameters restored from a backup, a cable replacement, electrical work in the cabinet, a storm. An SV0414 that shows up right after an intervention is usually a parameter that does not match the hardware or a connector not properly seated, not a new failure.
05Rule out the axis being mechanically jammed
If the axis can be moved safely, check in jog at low feed that it turns freely with no tight spots. A jammed axis forces the amplifier to full current and can cause overcurrent detection. If it is jammed, you have your starting point and it is mechanical, not electronic.
06Hand the case to maintenance with the data in order
Axis, number and sub-code, exactly when it appears, what was touched beforehand and whether there are other simultaneous alarms. From here on, measuring cables, checking the amplifier, comparing servo parameters against the builder's copy or replacing components is electrical maintenance work with the machine locked out and with a parameter backup taken first.
A mismatch between parameters and hardware. Confirm it by comparing the backup that was used against the one that belongs to that specific machine and by checking the actual motor and amplifier models fitted. It is solved by loading the correct copy, always backing up the current state before touching anything.
Suspect a cable or connector: chafing in a cable carrier, a loose shield or a connector making marginal contact. Confirm it by logging occurrences and seeing whether they cluster around moves that take the carrier to one particular position. The wiring inspection is maintenance work.
Regeneration: braking a large mass feeds energy back into the bus and the voltage rises. It is confirmed because it goes away when you reduce the rapid override. The cause may be in the braking resistor or in the power supply module, and maintenance checks it.
A machine parameter backup that is saved, dated and proven, with a copy kept off the machine; without that, any servo incident turns into a lost day. Cable carrier and cable inspection inside the maintenance plan, because chafing is the silent enemy behind this alarm. Clean cabinet filters and controlled temperature. And protection of the shop supply against voltage dips if the history shows alarms coinciding with other machines starting or with storms.
Fanuc detects a digital servo system fault on the specified axis. It is an alarm from the Servo / ejes area, and in the catalog it is listed as “Digital servo detection error”. On the machine you notice it like this: Axis alarm when turning on or moving, It may be accompanied by subcodes in diagnosis, The servo does not become ready.
On the shop floor it almost always comes from one of these causes: Damaged power or encoder cable, Servo amplifier faulty, Overcurrent or undervoltage, Incorrect servo parameters. Rule out the most likely one on your machine first, before touching parameters or swapping anything.
Reset just to confirm if it was temporary; If it comes back, stop. Resetting without fixing the cause first only hides the problem: SV0414 trips again and, in the meantime, you keep working with the machine in bad shape.
With the machine stopped and in a safe state, start with these checks: Note the axis and check diagnostics 200/204 if applicable, Check the amplifier alarms, Check visible connectors with the machine stopped. That alone will tell you whether it is the program or whether you need to raise a maintenance job.
With SV0414 active, avoid this: Do not bypass safety devices, Do not manipulate energized electrical cabinet, Do not continue producing if the alarm reappears. Skipping any of these points is what turns a minor stop into an expensive breakdown.
Practically always if it returns after reset, because it usually requires drive/axis diagnosis. If you are not sure how far it goes, stop the machine and report it: a repeat alarm always works out cheaper than a crash.
It is critical: there is a real risk of damage to the machine, the tool or a person. Leave the machine stopped, do not keep resetting it to see if it goes away, and call maintenance before producing again. Guidance reference. Always confirm the full text in the exact machine/control manual.
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