On a FANUC 31i, WN57 = “Override function is active” is usually not a hardware failure.
This warning means the PMC ladder override/debug mode is turned ON, or the machine builder intentionally left an override/force function active in the ladder.
Most common real-world cause
On machine tools, this usually happens after one of these:
1) Wrong PMC ladder loaded ⚠️
This is the #1 cause.
If someone:
- loaded SRAM backup from another machine
- restored wrong PMC
- loaded wrong ladder version
- changed ladder during troubleshooting
the control may boot with:
WN57 OVERRIDE FUNCTION IS ACTIVE
This exactly matches cases where the ladder program is broken or wrong machine backup was loaded.
2) Ladder debug “force” left enabled
If a tech used:
- FANUC LADDER III
- on-control ladder edit
- PMC signal force
- override/monitor debug
and didn’t disable it, WN57 stays active
How to clear it
First check PMC ladder status
Go to:
SYSTEM → PMC → PMCDGN
Look for:
- forced R bits
- forced G bits
- keep relays unexpectedly ON
- machine ready chain bypassed
Especially:
- feed hold
- door interlock
- hydraulic ready
- spindle orientation ready
- machine ready
Check if wrong ladder was loaded
Go to:
SYSTEM → PMC → VERSION / LADDER CHECK
Confirm:
- correct machine builder ladder name
- correct ladder size
- no parity or ladder broken warnings
- machine MTB version matches
If this happened after restore:
reload the correct SRAM + PMC backup from this exact machine
My honest FANUC repair answer
Because this is a 31i control, WN57 is very often caused by the wrong SRAM/PMC image.
I have seen this exact warning after:
loading backup from another Doosan / Mori / Okuma-FANUC machine.
The machine may still power up, but:
- overrides act strange
- machine ready missing
- spindle not enabling
- ladder broken alarms later
Best next move
I would first verify:
Did anyone recently load SRAM, FROM, or PMC backup?
If yes, that is almost certainly the source.
