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Two different situations under one heading. One is the notice that parameter write is enabled, which is a warning so it does not get left that way. The other is a memory error during an edit, which is more serious and usually forces a memory clear operation with data loss if there is no backup.
For reference only: alarms change with the manufacturer, the control and the machine PLC. Check the full code in the official manual before doing anything. Legal notice.
If there is program/parameter loss or persistent memory alarms.
Reset after switching PWE off or following the Fanuc controlled-clear procedure.
Choose the manual matching your control series, software version and machine builder. A support portal is a starting point; it does not establish applicability to every model.
The control protects its parameters with a logical write enable switch. While it is off, parameters cannot be modified by accident or by a macro; when somebody turns it on to make an adjustment, the control shows a permanent notice until it is turned off again. That notice is not a fault: it is a deliberate reminder, because a machine running with write enabled is a machine where any wrong keypress can change a critical parameter. The second situation is of a different nature. Programs and parameters live in a memory that is updated while editing; if the supply is cut right in the middle of that write, or if the battery backing that memory has run flat, the internal structures can be left inconsistent: a directory entry with no content, or sizes that do not add up. The control detects it at power-up or when you try to edit, and complains. The only real way out in those cases is usually a memory clear operation using the builder's procedure, which re-establishes the structures but erases what was there, which is why the whole weight of the solution falls on having a valid backup. So here the correct order is always backup first, procedure afterwards.
In order, from the fastest and cheapest check to the most expensive.
01First tell which of the two it is
If the message says parameter write is enabled and the machine is otherwise working normally, it is the notice. If the message appears after a power cut, at start-up, or when you try to edit, and comes with programs missing or odd behaviour, it is memory. The treatment is completely different.
02If it is the write notice, turn it off
Put the parameter write switch back to its normal position from the relevant control screen. Also ask who enabled it and what for: if parameters were adjusted, it is worth knowing which, and writing it down. A machine should not be producing with write enabled.
03If it is memory, take a backup before touching anything
Even with the memory damaged, get out what you can: programs, parameters, tool offsets, work offsets and macro data. Any partial copy is better than none. If the transfer also fails, tell maintenance before attempting any fixes.
04Check how far the damage goes
List the programs: see whether they are all there, whether any has an odd size or will not open. Check work offsets and tool offsets against the values written on the setup sheets. Damage limited to one program is solved by reloading it; damage that reaches parameters and offsets is another order of magnitude.
05Do not run memory clear procedures on your own
Control memory erase and re-initialisation operations are done with a key combination at power-up and delete data irreversibly. Running them without understanding the scope or having a backup is how you turn a bad day into a bad week. That is done by maintenance or the service engineer, with the good copy in hand.
06Check the control battery if the damage was spontaneous
If nobody switched anything off mid-edit and corruption appeared anyway, suspect the battery backing the memory. It is checked and changed by maintenance, and it is worth doing before restoring data so it is not lost again.
Somebody made an adjustment and did not put it back. Confirm it by asking and by comparing the parameters against the last backup to see whether anything changed. Turn write off and document any change found.
An interrupted memory write. It is confirmed because the program that was being edited is the one that shows up damaged. Normally it is enough to delete it and reload it from the server copy, touching nothing else.
A flat control battery or memory in bad shape. Confirm it by checking battery warnings and the date of the last change. It means a battery change and a restore from backup by maintenance; in the meantime, do not run critical jobs on that machine.
Parameter write enabled only for as long as the adjustment takes, and turned off immediately afterwards, with the change noted in a log. A complete backup per machine, dated and stored off the machine, including programs, parameters, tool offsets and work offsets. Control batteries changed by calendar. Avoid editing programs at the machine during operations where the supply could be cut, and never switch the control off with the editor open. And setup sheets with work offsets and tool offsets recorded, which is what lets you recover in half an hour what otherwise costs a day.
Fanuc warns of parameter writing enabled or memory error during editing. It is an alarm from the Program area, and in the catalog it is listed as “Parameter write enable / clear memory”. On the machine you notice it like this: PWE active, Alarm after power off during editing, Program or memory may become inconsistent.
On the shop floor it almost always comes from one of these causes: Write enable parameter left ON, Off during editing, Corrupt memory/program. Rule out the most likely one on your machine first, before touching parameters or swapping anything.
Reset after switching PWE off or following the Fanuc controlled-clear procedure. Resetting without fixing the cause first only hides the problem: PS100/PS101 trips again and, in the meantime, you keep working with the machine in bad shape.
With the machine stopped and in a safe state, start with these checks: Disable PWE if it is not adjusting, Back up programs/parameters, Identify affected program. That alone will tell you whether it is the program or whether you need to raise a maintenance job.
With PS100/PS101 active, avoid this: Do not bypass safety devices, Do not manipulate energized electrical cabinet, Do not continue producing if the alarm reappears. Skipping any of these points is what turns a minor stop into an expensive breakdown.
If there is program/parameter loss or persistent memory alarms. If you are not sure how far it goes, stop the machine and report it: a repeat alarm always works out cheaper than a crash.
It is a warning: the machine carries on, but it is flagging something that will get worse if you let it go. Deal with it between parts, not at the end of the shift. Guidance reference. Always confirm the full text in the exact machine/control manual.
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