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FANUC Alarm SRVO-204 — SYSTEM External(SVEMG abnormal) E-stop

Error
Hardware
emergency stop and dual safety chains
Controllers
R-J3iB / R-30iA / R-30iB
FANUC class
SYSTEM
Hardware family
FANUC emergency stop, pendant and dual safety chain alarms

FANUC SRVO-204 (“SYSTEM External(SVEMG abnormal) E-stop”): The external emergency stop push button is pressed and mis-wiring on SVEMG is detected. First check: Power off. Correct the wiring on SVEMG.

Updated 2026-10-22 · LogrobotLM reference

Description

The external emergency stop push button is pressed and mis-wiring on SVEMG is detected.

Remedy

Power off. Correct the wiring on SVEMG. If using external emergency stop, clear the source of the fault, and press RESET. Refer to the maintenance manual for details.

Field diagnosis

A press on the external device wired to EES was detected, yet the hardware stop chain remains closed: one EES channel did not follow the other.

What to check

  • Check the contact and the cable on both EES channels at the terminal block; replace the cable if it is suspect.
  • If the wiring is sound, the emergency stop board is at fault.
  • Back up the controller before replacing any board.
  • The code only clears after a power cycle.
  • Note: An external button with a single contact wired to both channels in parallel produces exactly this fault.

Related codes

SRVO-007SERVO External emergency stopsSRVO-270SERVO EXEMG1 status abnormalSRVO-271SERVO EXEMG2 status abnormalSRVO-231SERVO Chain 2 (0v) abnormalSRVO-202SERVO TP E-stop or SVEMG abnormalSRVO-203SVON input(SVEMG abnormal)

Indicative field information — the robot manufacturer's manual and safety procedures always prevail. Never bypass a safety device; apply lockout/tagout (LOTO) before any physical intervention. How this reference is built →