| Cause Category | Specific Issue | |----------------|----------------| | | Broken, shorted, or poorly shielded feedback cable (serial pulse path) | | Electrical Noise | EMI/RFI interference on the feedback line (improper grounding, high-power cables routed too close) | | Connector/Pin | Loose, oxidized, or bent pins at the motor encoder connector or amplifier JF1/JF2 port | | Power Supply | Fluctuating or insufficient 5V supply to the encoder | | Hardware Failure | Faulty serial encoder inside the motor, damaged servo amplifier serial interface, or main CPU board issue | | Battery/APC | (On absolute encoders) Low battery or lost absolute position data can sometimes manifest as a 366 alarm during power-up |
When the 366 alarm appears, the machine is typically in Emergency Stop (E-Stop) mode with servos disabled. fanuc 366 alarm
