Navigate to SYSTEM → PMC → DGN. Look for address DGN 445. This diagnostic shows the maximum scan time of the PMC.
Action: Zero out DGN 445 by pressing RESET while viewing it. Then watch how fast it climbs. If it jumps to 98% in 2 seconds, the overload is severe.
You cannot edit the ladder without the original PMC file (usually a .LAD or .MPF file from the machine builder). If you have it, here are the repairs.
If the alarm persists after a power cycle, you need the Fanuc PMC parameter and Ladder III software.
On newer controls, alarm 366 often appears when using an indirect argument assignment for a system variable incorrectly.
Wrong:
#500 = #4111 -> Fine.
G65 P1000 A#500 -> Fine.
But if #4111 returns a non-integer or illegal character, the macro call parser throws 366.
Fanuc PMCs have Level 1 (high speed, runs every 1–2ms) and Level 2 (low speed, runs every 8–16ms).
Follow these steps in order:
Even if it looks fine, replace the cable as a cheap and fast diagnostic step.
If the above steps fail, the spindle amplifier itself may be faulty. Swap with a known working unit (ensure same model).