Fanuc 7115 Alarm [FAST]

The FANUC 7115 alarm is almost never a hardware failure. Do not restart the control and hope it goes away—that just hides the bad code.

Instead, slow down, look at the specific line number, and check for typos or unsupported features. 9 times out of 10, you’ll find an extra period, a stray letter, or a missing decimal.

When to call service: Only after you have verified the code is 100% correct according to your machine’s option sheet. If the code is perfect but the alarm persists, you may have a corrupted parameter or a failing PMC, but that is rare.

Happy (and legal) machining!

Have a different FANUC alarm? Drop it in the comments below.

You are in G98 (feed per minute) and you call a canned cycle like G83 that expects G99 (feed per rev). Or you call a macro statement without the Macro B option.

The FANUC I/O Link is a daisy-chained network connecting the main CNC to remote I/O racks (e.g., I/O Unit A, I/O Unit B, or a handheld pendant). If a terminating resistor is missing, a cable is broken, or a slave unit (I/O module) loses power, the PMC will generate an 7115 alarm because it cannot "see" the expected hardware map. fanuc 7115 alarm

Older FANUCs (like 6M or 0T) are very picky. If you write X5 without a decimal, the control might read it as X0.0005 inches. A resulting value that is too small or illegal can trigger 7115.

Machine: FANUC 31i-A5 on a 5-axis mill. Symptom: Intermittent 7115 alarm only when the operator opened the safety door. Diagnosis: The I/O Link daisy-chained through a safety relay. The last I/O unit (at the pendant) had a loose terminator plug. Vibration from the door opening caused a momentary open circuit. Solution: Reseated the I/O Link terminator and tightened the screws. Replaced the low-quality terminator with a genuine FANUC part (A03B-0807-K001).

While many 7115 alarm causes are fixable in-house, certain scenarios require a factory-trained engineer. The FANUC 7115 alarm is almost never a hardware failure

Call for service if:

FANUC’s official part numbers for troubleshooting:

You tried to use G71 (OD roughing cycle) on a lathe that doesn’t have the "Automatic Operation – Multiple Repetitive Cycles" option. Or you used G12.1 (Polar Interpolation) on a mill that doesn’t have it enabled. Have a different FANUC alarm