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The machine is telling you one or more axes have not established their reference yet and that it will not let the automatic cycle start like that. It is not a fault: it is the protection that stops you working when the control does not know for certain where the axes are in machine coordinates.
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 the return fails repeatedly or the absolute battery does not retain position.
Reset and complete homing before operating.
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.
Everything that protects the machine in machine coordinates, starting with the software travel limits and going on to the forbidden zones the builder defines, depends on the control knowing each axis's real position. That knowledge is established by the reference return: until it is completed, the control has a relative position, useful for careful jogging, but not a trustworthy absolute position. So there is an explicit requirement to reference before operating in automatic, and the control checks it when the cycle is started. This message appears at three different moments and it is worth telling them apart. The first is the normal one: at power-up, before anybody has homed; that is routine. The second is after a servo alarm or an emergency stop, because cutting the axis excitation may have cost the control its certainty about position and it demands the reference be redone; there the message is a consequence, not the cause, and what matters is understanding why the previous alarm tripped. And the third is the worrying one: a machine with absolute pulse coders that normally does not need homing every morning and suddenly asks for it, which usually means the absolute position has been lost, typically from a flat battery. In that case re-establishing it is not a button press but following the builder's procedure.
In order, from the fastest and cheapest check to the most expensive.
01See which axes are unreferenced
The position display shows which axes have their reference mark. If they are all missing, it is a normal start-up. If only one is missing, that axis has something wrong: it lost reference through an alarm, through the battery, or through a problem in its homing sequence.
02Clear the travel path before homing
Check there is no part, vice, tool or tailstock in the way to the reference area, and that the spindle is stopped. Reference return drives axes towards the extremes, and doing it with something in the way is the usual way of turning a routine into a crash.
03Home using the machine's procedure and order
Many machines have a mandatory order, nearly always starting with the vertical axis so the tool is lifted before anything else moves. That order is in the machine manual. Respect it even if the control lets you do it another way.
04If an axis will not home, do not keep trying
Repeating homing over and over against an obstruction or with a faulty detector only makes things worse. If an axis does not capture its zero, note the behaviour (whether it decelerates on entering the zone or not) and pass it to maintenance with that fact.
05If it is an absolute machine that never asked before, look at the battery
A machine that normally retains its position and suddenly demands homing has usually lost its backup. Look for battery warnings and the date of the last change. Re-establishing the absolute reference is done by the builder's procedure, not by adjusting values by eye.
06Verify zero before producing
With the reference done, check against a known point that the machine coordinates are what they always were, especially if there was a position loss or an intervention. A reference established in the wrong place gives no alarm: it gives shifted parts.
Expected behaviour on machines with dog-based homing. It is confirmed because it is identical every day and it is cleared with the usual routine. There is nothing to fix, only to do it in the right order.
The axis lost its position certainty when the excitation was cut. It is confirmed because the previous alarm is there in the history. What matters is diagnosing that alarm; this message is only the consequence.
Absolute position lost through a flat battery or a retention cable. Confirm it by looking for battery warnings and checking their date. It means a battery change and re-establishment by the builder's procedure.
A written start-up routine, visible at the machine, with the axis homing order. Axes parked at a known, clear position at the end of the shift so the next day's homing is always the same. Encoder batteries changed by calendar on machines with absolute pulse coders. The reference re-establishment procedure printed and kept next to the machine. And verification of zero against a known physical point every time there has been a position loss or work on an axis.
Fanuc warns that the machine needs to establish homing before operating automatically. It is an alarm from the Sobrecarrera area, and in the catalog it is listed as “Return to zero not completed”. On the machine you notice it like this: Does not allow automatic cycle to start, Appears after starting or after servo alarm, Requests return to zero.
On the shop floor it almost always comes from one of these causes: Machine without homing after turning on, Reference loss due to servo alarm, Absolute encoder battery dead, Axis did not complete return. Rule out the most likely one on your machine first, before touching parameters or swapping anything.
Reset and complete homing before operating. Resetting without fixing the cause first only hides the problem: PS0224 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: Check that the axis travel is clear, Perform the return to zero in slow manual mode, Note the pending axis. That alone will tell you whether it is the program or whether you need to raise a maintenance job.
With PS0224 active, avoid this: Do not start automatic cycle without reference, Do not skip the homing sequence. Skipping any of these points is what turns a minor stop into an expensive breakdown.
If the return fails repeatedly or the absolute battery does not retain position. 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 stop alarm: the cycle will not continue until you fix the cause. It does not always mean serious damage, but it leaves the machine where it is and you have to check it before running again. Guidance reference. Always confirm the full text in the exact machine/control manual.
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