Servos, axes and encoders
These cover amplifier faults, loss of reference, encoder problems, over-travel, mechanical jams or an axis not ready. Before moving the machine, identify the axis, sub-code and drive status.
CNC alarm codes and troubleshooting guide
Enter the error code or symptom to find the cause and how to repair it at the machine.
This CNC alarm manual gathers indicative references for Fanuc, Haas, Siemens, Heidenhain, Mazak, Okuma and Mitsubishi controls. Search by code, brand, machine area or symptom to review likely causes, safe checks and criteria for deciding when to call maintenance. Before resetting, moving axes or intervening, always confirm the full code and the procedure in your machine's official manual.
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.
Fanuc/OEM warns of low battery or loss of reference in absolute encoder.
Fanuc reports communication errors, frame or low battery of the absolute pulse coder.
Fanuc reports a DS category fault (integrated alarms that combine drive and CNC conditions).
Fanuc reports an internal fault or PMC/PLC watchdog.
Fanuc detects FSSB optical communication problem between CNC and amplifiers.
Fanuc detects initialization/configuration failure of the FSSB servo bus between CNC and amplifiers.
Haas detects that the machine did not complete zero return upon power-up or after an alarm.
The Haas control detects communication or memory failure with the board/motion control.
Haas indicates that the servos are disabled or not ready.
Haas detects excessive tracking error in X/Y/Z/A according to alarm number.
Haas detects the emergency stop pressed or the E-stop circuit open.
Haas detects prolonged excessive consumption of the servo of the indicated axis, characteristic of jamming or mechanical loading.
Haas detects internal interrupt/control fault that prevents normal operation.
The machine detects that an axis is not correctly aligned or referenced to continue.
The bus or electrical input exceeds the allowed range and the machine disables systems.
The Haas machine does not detect sufficient air pressure to operate systems.
Haas detects insufficient level/pressure in the lubrication system or associated pressure.
The Haas brake resistor/regeneration circuit overheats.
The control receives a fault condition from the spindle drive/vector drive.
Haas reports a low backup battery for memory or settings, depending on the control generation.
Alarms by control brand
Every control numbers and describes its alarms in its own way. Go into the brand of your machine to see the full list with the meaning of each code.
What are CNC alarms and how are they interpreted?
CNC alarms are diagnostic messages that stop or limit the machine when the control detects a problem with the program, servo, spindle, safety, PLC, lubrication, coolant or axis travel. The same code can mean different things depending on the manufacturer, control series, machine and installed options, so it must always be checked against the official manual before resetting or intervening.
Main categories of CNC alarms
Spindle, power and coolant
These group spindle overload, orientation, inverter, temperature, and lack of coolant or lubrication. Check the cutting load, ventilation, fluid levels and the drive's auxiliary alarms.
Program, cycles and syntax
They appear because of unsupported G/M codes, badly parameterised cycles, missing subprograms, wrong offsets or a post-processor set up for another control.
Safety, doors and PLC
These include emergency stops, doors, interlocks, air pressure, the ATC, sensors or machine logic. Safety devices must never be bypassed to keep production running.
Frequently asked questions about CNC alarms
What do I do if the RESET button does not clear the control alarm?
Some safety alarms, such as servo faults, hard limits or emergency stops, latch in the system. To clear them you must first fix the root cause, for example removing chips from a sensor, then switch the machine fully off at the main breaker and power it up again following the manufacturer's procedure.
What does the APC/Encoder low battery alarm mean and how to fix it?
Esta alarma indica que la pila que conserva la posición de los ejes o encoder absoluto está casi agotada. Normalmente hay un margen limitado para cambiarla. La sustitución debe hacerse siguiendo el manual oficial; en muchas máquinas se realiza con la máquina encendida y en parada de emergencia para no perder referencias. Si se apaga sin batería válida, el control puede perder cero máquina, límites de carrera o referencias de ejes.
How do I clear an Over Travel or Hardware Limit alarm?
Over-travel appears when an axis reaches the safety limit switch. To free it you normally switch to manual JOG or handwheel/MPG, hold the limit override or OT Release/Limit Override button if the machine has one, and move the blocked axis away from the stop. Do it at low feed and check the machine manual.
Why does an alarm go off when trying to change the M06 tool?
Failures during M06 or turret indexing are usually caused by insufficient pneumatic or hydraulic pressure, inductive sensors fouled by coolant or chips, or axes away from the reference point required for the change. Before editing the program, check pressure, sensors, ATC/turret status and the G28 or G30 return position for your machine.
When should I stop intervening and call the SAT technical service?
Stop and call service for alarms about lost parameters, memory or parity errors, short circuits in amplifier modules, SPM/SVM/PSM alarms on Fanuc, a burning smell, blown fuses or continuous spindle overheating. Insisting with resets can make faults in boards, drives or motors worse.
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