If an operator or technician has forced a diagnostic bit (e.g., G54.0) using the PMC Maintenance screen and then saves the ladder while that force is active, the system may reboot with a logical inconsistency. The 7115 alarm appears because a forced coil exists in a state that violates the ladder’s normal logic flow.
At its core, the 7115 alarm is a feedback loop failure. The CNC controller sends a command to the Fanuc servo drive, which in turn moves the motor. When the actual position reported by the encoder differs too significantly from the commanded position—often due to mechanical resistance or electrical glitches—the system triggers the 7115 code to prevent damage. Primary Causes fanuc 7115 alarm