The FANUC 0i series (0i-A/B/C and 0i-Mate) is one of the most common FANUC control families on shop floors today. Its alarm logic largely follows the classic FANUC structure; however, because the 0i architecture uses the FSSB (serial servo bus) and a serial spindle link, it has alarms of its own, and some system alarm numbers carry different meanings than on the older 0 series. On this page you will find only the alarms and differences specific to 0i / 0i-Mate; for the full map of alarm groups shared by all series, see our main guide: FANUC Alarm Codes and Solutions.
What Is Different on 0i / 0i-Mate? (Summary)
Four things set this series apart. First, the servo drives connect to the control over a fibre-optic FSSB line, so FSSB alarms appear in the 5134–5198 range. Second, the spindle drive communicates over a serial link, making alarms 749/750 specific to this family. Third, the 900–976 system alarms are renumbered (ROM/DRAM/SRAM parity, PMC, NMI, bus errors). Fourth, the 0i keeps a System Alarm History screen: details of system alarms that disappear after a power cycle can still be read there — gold when briefing service.
Alarms Specific to or Different on 0i / 0i-Mate
| Code | Meaning and how to approach it |
|---|---|
| 90 | Reference return completed abnormally. The axis may have started homing from too short a distance, or the encoder one-rotation signal is not being read; move the axis away and retry, and if it repeats have the encoder and cabling checked. |
| 300 | Reference return request: the absolute encoder has lost its position (usually after battery replacement/discharge). Re-reference the axes. |
| 401 / 404 | V-READY off / V-READY unexpectedly on: a break in the servo-ready chain (E-stop, MCC, drive power, FSSB). Proceed exactly as in the servo section of the main guide. |
| 417 | Digital servo system abnormal: an invalid servo parameter value (motor type, direction, pulse settings). Undo the last parameter change; if none was made, verify the servo parameter set with service. |
| 462 / 463 | CNC data send / slave data send failed: data could not reach the drive over the FSSB line. Check the fibre-optic connectors, their latches and the drive power. |
| 700 / 701 | Overheat — 700 control unit, 701 fan motor: clean cabinet fans and filters, verify the fan spins, check the cabinet cooler. One of the most common alarms in summer. |
| 704 | Spindle speed fluctuation detected: RPM deviates under cutting load. Check belt tension, tooling/cutting conditions and the spindle drive. |
| 749 | Serial spindle communication error: the serial link between control and spindle drive dropped. Check the link cable, shielding and drive status; electrical noise is a frequent cause. |
| 750 | Spindle serial link start-up failure: the spindle drive did not become ready at power-up. Check whether the drive powers up and shows an error code; verify the power-up sequence (drive first, then NC). |
| 5134–5198 | The FSSB alarm family — 5134 open-ready timeout, 5135 error mode, 5136 number of amplifiers too small (one drive is not seen), 5137 configuration error, 5197 open timeout, 5198 ID data not read. Common approach: check the fibre-optic FSSB cable, drive power supplies and the axis–amplifier assignment parameters. With 5136, one drive is most likely not receiving power. |
| 926 | FSSB bus alarm (system level): a serious communication fault on the line. If it survives a power cycle, the fibre line and drive boards need service attention. |
0i System Alarms (900–976): Renumbered vs the Old 0 Series
| Code | Meaning on the 0i series |
|---|---|
| 900 | ROM parity error. |
| 912–919 | DRAM parity errors. |
| 920 | Servo alarm / watchdog (broader than on the 0 series — covers servo-side system faults, not only the main board). |
| 930 | CPU interrupt alarm. |
| 935 | SRAM ECC error — a bad memory cell; this is exactly why your program/parameter backup must be current. |
| 950 / 951 | PMC system alarm / PMC watchdog alarm. Careful: on the old 0 series, 950 is a +24V fuse failure — do not mix the series up. |
| 972 / 973 | NMI alarms: 972 on an option board (0i-B only), 973 of unknown cause. |
| 974–976 | F-BUS / bus / local bus errors — board-level communication faults, a service matter. |
Use the System Alarm History Screen
The 0i’s greatest gift to the operator is that alongside the standard alarm history it keeps a system alarm history: even when a system alarm such as 930 disappears from the screen after a power cycle, its details (which board, which address) remain readable there. Opening that screen and noting the details before calling service shortens downtime considerably. For the screens themselves, see FANUC Alarm, Message and Diagnosis Screens. P/S (program) alarms are shared across series — see the P/S Alarm Codes list, and for the parameter side our Comprehensive FANUC Parameter Guide.
Frequently Asked Questions
How do I tell whether my machine is 0i or 0i-Mate?
The series name is shown on the boot screen and the SYSTEM screen (e.g. Series 0i-MC, 0i Mate-TC). The 0i-Mate is the economy version of the 0i with fewer axes and options; the alarm structure is the same.
I get FSSB alarm 5136 and the machine will not start — where do I begin?
5136 usually means one of the drives is not receiving power. In order: are the LEDs on each drive lit, are the drive fuses/power feeds intact, and is the fibre-optic FSSB cable clicked firmly home at both ends? These three checks resolve the majority of cases.
Other series guides: If your machine runs a 21i/21i-TB or 18i control, see our FANUC 21i / 21i-TB Alarms page.
On the operator side: For what to do about each cycle, overtravel, servo, spindle and battery alarm an operator actually meets, see our FANUC Operator Alarms page. If the alarm comes from a programming error, the FANUC G and M Code List also helps.