Fanuc 366 Alarm Page

The (frequently displayed as SV0366 n AXIS: PULSE LOSS (INT) ) is a critical servo alarm indicating that the CNC system has detected a pulse loss in the built-in pulse coder of the specified axis (

Coolant ingress frequently shorts out optical and magnetic encoders. Remove the rear cap of the affected servo motor. Inspect the encoder area for oil, moisture, or residue.

Ensure the shielding of the feedback cable is properly grounded to the cabinet chassis. fanuc 366 alarm

A sudden CNC machine stoppage can halt production and impact your bottom line. Among the various servo alerts on FANUC control systems, the is a common issue that specifically indicates a pulse coder position missing error.

Your CNC control sends a command to the servo motor to move. The motor spins, and a device called a Pulse Coder (or encoder) attached to the motor shaft measures exactly how far it turned. It sends this data back to the control via a feedback cable. The (frequently displayed as SV0366 n AXIS: PULSE

Always perform a full power cycle after changing servo parameters to ensure they take effect.

To understand the alarm, it helps to know how a servo motor reports its position. The motor uses an internal device called an encoder (or pulse coder) to send rotational position and speed data back to the CNC control. The "Pulse Miss" error means the drive detected a loss of pulse data integrity. It doesn't necessarily indicate a complete loss of communication but rather that the quadrature signals (A/B phases) or the absolute serial data checksum failed momentarily. In simple terms, the CNC gave a command to move, but the feedback signal it received back was corrupted or lost, causing the control to trigger an immediate safety stop. Ensure the shielding of the feedback cable is

If the machine uses a linear scale or if the motor's pulse coder is exposed, check for grease or coolant buildup. Cleaning the scale or coder can often resolve "missed pulse" errors. 2. Diagnostic Swapping

A pulse coder (encoder) is built into the servo motor and measures the motor's rotation. An external scale (linear scale) is mounted to the machine's table and measures table position directly. If the scale is the master feedback, the control compares motor rotation to scale position. If they don't match, you may get a 366 or 367 alarm.

: Verify the amplifier wiring and ensure the feedback cables are securely connected and undamaged. Process of Elimination Swap Drives