Applicable Systems
Series 0i
Series 16/18/21
Alpha
Beta
Symptoms
Alarm 999: ROM pair error (No correspondence between high and low). The Fanuc Series 6M/6T CNC system displays this alarm on the operator panel.
Possible Causes
- Refer to the machine manual for detailed cause analysis
- Check related sensors, switches, and parameters
Troubleshooting Steps
- Step 1: Read alarm 999 on the CNC display and note the full alarm message
Alarm code and description displayed for diagnosis - Step 2: Check the machine status and identify any obvious mechanical, electrical, or pneumatic issues
Visible faults identified or confirmed as intermittent - Step 3: Consult the manufacturer manual for alarm-specific troubleshooting procedures
Root cause identified per manufacturer guidelines - Step 4: Apply the recommended fix and reset the alarm
Alarm cleared and machine resumed normal operation
How to Reset
To reset alarm 999: 1) Address the root cause. 2) Press the RESET key on the CNC panel. 3) If the alarm persists, cycle power to the control. Caution: Repeated alarms without fixing the cause may cause damage.
Frequently Asked Questions
- Q: What does alarm 999 mean?
Alarm 999 corresponds to: ROM pair error (No correspondence between high and low). This is a Series 6M/6T system alarm that typically requires checking machine state and the manufacturer manual.
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Source: HelmanCNC.com - https://www.helmancnc.com/fanuc-6-alarms-fanuc-6m-6t-alarm-codes/
Category: CNC
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