Photograph the complete warning and note whether it appeared during homing, heating, leveling or printing. Neptune 4, Pro, Plus and Max firmware must not be mixed.
Begin with reversible checks: remove an obstruction, reseat the PEI sheet, clean the probe area or test a known USB file when the message points there. Restart once only after the machine is cool and the cause has been inspected.
Heating, thermistor and mains warnings require a stop. Do not bypass a sensor or continue a print with unstable temperature. Use Elegoo’s Neptune support and provide the exact model, firmware and screen text.
An error index cannot safely invent a number that Elegoo has not assigned. The full message is the lookup key.
Many warnings trace back to routine wear rather than a defect — the maintenance schedule covers the inspection points worth checking first. If a specific warning points to nozzle temperature or extrusion, the nozzle replacement guide explains when a worn nozzle rather than a setting is the actual cause. Elegoo’s enclosed CoreXY printer, the Centauri Carbon, documents a similar but separate numeric error index. Elegoo’s newer Neptune 5 doesn’t yet have its own documented error list and currently points back to these Neptune 4 series entries as a starting reference.
The base Neptune 4 error and warning index covers the entry-level model’s own Klipper shutdown messages, most of which match the Pro’s documented faults.
The larger Neptune 4 Max shares this firmware track too; see the Elegoo Neptune 4 Max Error Code Index for its own documented fault set.