Top FANUC CNC Error Codes Explained and How To Fix

FANUC controls are everywhere - mills, lathes, grinders, robots, and entire production lines. That also means FANUC alarm codes are among the most searched CNC topics globally. Operators, maintenance engineers, and production managers usually see the same patterns of faults repeating.

FANUC Alarm 401 - Servo Alarm: Excess Error

What it means
The axis position error exceeded the allowable limit. The machine cannot reach the commanded position fast enough.

Common causes

• Mechanical binding on the axis
• Ballscrew or linear guide contamination
• Servo motor overload
• Aggressive feedrate or acceleration
• Encoder or cable issues

How to fix

• Jog the axis slowly and listen for abnormal noise
• Inspect way covers, guides, and lubrication
• Reduce rapid or cutting feed temporarily
• Check servo load and following error parameters
• Inspect encoder cables and connectors

FANUC Alarm 414 - Servo Alarm: Detecting Excess Load

What it means
The servo motor is drawing too much current.

Common causes

• Axis crash history
• Mechanical resistance
• Tool or fixture collision
• Poor lubrication
• Servo motor failure

How to fix

• Power off and manually check axis movement
• Inspect lubrication system operation
• Verify no chips or debris are trapped
• Check motor temperature and servo drive alarms
• If persistent, test motor and amplifier

FANUC Alarm 510 - Spindle Alarm

What it means
The spindle system detected an abnormal condition.

Common causes

• Overloaded spindle during cutting
• Tool imbalance or worn tool
• Spindle drive fault
• Cooling fan or chiller issue

How to fix

• Reduce spindle load and cutting parameters
• Check tool holder and balance
• Inspect spindle drive diagnostics
• Verify spindle cooling and fans are running

FANUC Alarm 2040 - PMC Alarm

What it means
A ladder logic or I/O condition is not satisfied.

Common causes

• Door, chuck, or safety interlock not confirmed
• Hydraulic or pneumatic pressure missing
• Sensor or limit switch failure

How to fix

• Check operator messages on the screen
• Verify hydraulic and air pressure levels
• Inspect sensors and limit switches
• Use PMC diagnostics to identify missing signals

FANUC Alarm 300 - Overtravel Alarm

What it means
The axis hit a soft or hard travel limit.

Common causes

• Incorrect work offset
• Program error
• Home position drift
• Limit switch activation

How to fix

• Switch to handle or jog mode
• Move axis away from the limit
• Verify work offsets and program zero
• Re-home the machine if required

FANUC Alarm 1013 / 1014 - Communication Alarm

What it means
Communication between CNC, servo drives, or spindle drives failed.

Common causes

• Loose fiber optic cable
• Electrical noise
• Power fluctuation
• Drive failure

How to fix

• Power off and reseat fiber cables
• Inspect for damaged connectors
• Check grounding and cabinet cooling
• Review drive diagnostics before restart

FANUC Alarm 700 - Parameter Write Enable On

What it means
The control is in parameter edit mode, which blocks operation.

Common causes

• PWE left enabled after service
• Incorrect startup procedure

How to fix

• Turn PWE off in the parameter screen
• Power cycle the machine
• Confirm no parameters were unintentionally changed

FANUC Alarm 909 - Program Number Not Found

What it means
The CNC cannot find the requested program.

Common causes

• Incorrect program number call
• Program not loaded
• Memory device not mounted

How to fix

• Verify program number format
• Confirm the program exists in memory
• Check USB, CF card, or network connection

Final Takeaway

FANUC alarm codes are consistent, logical, and extremely well documented once you know where to look. The fastest fixes usually come from checking mechanics, load, and interlocks before touching parameters.

About MDCplus

Our key features are real-time machine monitoring for swift issue resolution, power consumption tracking to promote sustainability, computerized maintenance management to reduce downtime, and vibration diagnostics for predictive maintenance. MDCplus's solutions are tailored for diverse industries, including aerospace, automotive, precision machining, and heavy industry. By delivering actionable insights and fostering seamless integration, we empower manufacturers to boost Overall Equipment Effectiveness (OEE), reduce operational costs, and achieve sustainable growth along with future planning.