What causes FANUC alarm 918?

Machine system or function indicated by the alarm name has detected a fault. Control parameter or configuration error related to the alarm condition. Hardware component fault on the CNC or machine. Part program error or illegal operation for the indicated function. Machine interlock or safety condition not satisfied.

How do I fix FANUC alarm 918?

1. Note the alarm number and check the Fanuc alarm screen for any sub-code or additional details. 2. Identify the specific machine system or function from the alarm name. 3. Power cycle the machine to clear transient faults. 4. Consult the Fanuc parameter or operator manual for alarm 918 specific remedy. 5. Contact Fanuc service if the alarm persists after basic troubleshooting.

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FANUC Controller

System · Intermediate · 30-60 minutes

Alarm 918

Fanuc Alarm 918 - DRAM PARITY: BYTE 6

Fanuc Alarm 918 DRAM PARITY BYTE 6 indicates a hardware-level memory failure on the main CPU board, specifically in the sixth byte of the DRAM memory array. This is a critical hardware fault that typically requires main CPU board replacement, as the DRAM is soldered directly to the board and cannot be individually replaced.

FANUCSystemIntermediate30-60 minutes

918

Fanuc Alarm 918 - DRAM PARITY: BYTE 6

SYSTEM ALARM 918

Root Cause Summary

Fanuc Alarm 918 DRAM PARITY BYTE 6 indicates a hardware-level memory failure on the main CPU board, specifically in the sixth byte of the DRAM memory array. This is a critical hardware fault that typically requires main CPU board replacement, as the DRAM is soldered directly to the board and cannot be individually replaced.

Causes and Fixes

1
Power cycle the CNC completely - turn OFF main breaker, wait 60 seconds, then power ON. If alarm clears temporarily but returns, this confirms intermittent DRAM failure requiring board replacement.
Back up all CNC parameters, programs, and offset data to memory card or via RS232 before proceeding, as board replacement will require data restoration.
2
Check SYSTEM > ALARM log to determine if alarm 918 is recurring or isolated. Note exact time stamps and any pattern (power-on only, random during operation, or after specific operations).
3
Verify main CPU board part number and serial number. For 0i series: typically A20B-8100-xxxx or A20B-8200-xxxx. For 30i/31i/32i series: A20B-8100-xxxx, A20B-8101-xxxx, or A02B-0319-xxxx depending on model.
4
Replace main CPU board with correct revision matched to current control software version. After installation, reload all backed-up parameters and perform full system initialization per Fanuc maintenance manual procedures.
Ensure replacement board firmware/software version matches or is compatible with current system. Version mismatch can cause additional alarms or system instability.

Service Recommendedlow confidence

Call a technician if:

·DRAM replacement required
·CPU board replacement needed
·Persistent alarm after basic troubleshooting
·No experience with CPU board handling

Prevention

Maintain stable power supply voltages
Ensure proper EMI shielding and grounding
Keep control cabinet temperature below 40°C
Perform regular backup of system parameters
Schedule preventive maintenance of cooling systems

Common Mistakes

Handling memory modules without anti-static precautions
Ignoring power supply voltage quality
Not checking for EMI sources
Attempting to repair CPU board components
Failing to backup data before hardware replacement

Related Alarms

917 919 920 921 922 923 924 925

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Always verify with your machine manual or a certified technician before performing service procedures.