A note on the model name and error framework
QIDI is not fully consistent about how it labels this printer. The product itself ships as the “QIDI Plus 4,” which is the name used on the eMMC recovery image download and in general marketing. QIDI’s own wiki hosts the documentation hub under the title “X-Plus4” (rendered “X-Plus 4” in body text), while a handful of troubleshooting pages sit under a separate “PLUS4” URL path, and after-sales contact addresses use Plus4support@qidi3d.com. All of these refer to the same machine. This guide uses “Plus 4” and “X-Plus4” interchangeably, matching QIDI’s own inconsistency, so search results line up regardless of which spelling you used to find this page.
On the error code side, QIDI runs two separate systems. QDE is the older numbered format (for example QDE_004_001), and it is documented on a shared QIDI BOX page rather than a per-printer page, since these codes come from the BOX hub’s own sensors. QDC (QIDI Diagnostic Center) is the newer, longer segmented format, such as QDC_200_001_010_001, and it is meant to cover mechanical, toolhead, BOX, network, and AI camera faults across QIDI’s current Klipper-based machines. The Plus 4 runs Klipper and Moonraker with a Fluidd web interface, the same base platform as the Max4, which places it in the same generation as the QDC system rather than the older screen-only error tables used on machines like the X-Smart3 or X-Plus3. That said, as of this writing the public QDC index at wiki.qidi3d.com/en/QDC lists detail pages tagged only for the Max4. No Plus4-tagged QDC pages are live yet, and there is no standalone “Plus4 Error Code” list comparable to the one QIDI publishes for the Q2. That gap is real and worth knowing before you go hunting for a code that matches exactly what’s on your screen.
QIDI BOX and filament handling faults
If you run the Plus 4 with a QIDI BOX multi-material unit, the BOX hub itself generates a set of QDE_004 codes when filament fails to move through it correctly. These include QDE_004_001 through QDE_004_026, covering situations like filament not passing through the BOX hub sensor during a feed, the hub detecting filament already present when you try to load, a failed return or unload, tangled or wrapped filament jamming the four-in-one hub, and RFID read failures when no tag is detected. QIDI documents these under a shared BOX page rather than a Plus4-specific one, and the wiki explicitly warns that the Plus 4’s BOX hub data cable is physically different from the Q2 and Max4 cables and should not be swapped. Because of that hardware difference, treat these QDE codes as the documented behavior of the BOX accessory generally rather than a confirmed one-to-one match for the Plus 4’s exact firmware build. The first practical check for any of them is the same regardless: remove the front cover, check whether filament is visibly stuck or coiled inside the four-in-one hub, and confirm the hub’s status LED is lit (blue normally means the path is clear, off usually means filament is still inside). Most of these faults clear with TRYMOVE_AGAIN in the Klipper console once the physical jam is cleared, or with a manual retract of the filament before retrying.
Toolhead, extrusion and clog faults
QIDI’s Plus 4 manual pages describe filament clogs as occurring either in the extruder gearbox or in the hotend itself, without assigning either one a QDC or QDE number. If prints stop extruding mid-job or filament grinds without feeding, the first check is whether the filament is cut cleanly above the extruder and whether the hotend cable is routed clear of the cooling fan, since a pinched cable is a common cause of erratic thermal or fan readings. QIDI’s documented fix path for a clog is mechanical: cut the filament, remove the two hotend mounting screws, pull the hotend, and either clear the extruder gearbox or heat the nozzle to printing temperature and manually withdraw the softened filament. There is no software error message tied to this fault on the current Plus4 pages, it is described purely as a physical symptom to diagnose by inspection.
Bed adhesion and Z offset faults
Poor first-layer adhesion on the Plus 4 is documented as a Z offset issue rather than a coded fault. If the first layer shows visible gaps between lines, the nozzle is too far from the plate; if it drags or scrapes, it is too close. QIDI’s recommended first check is to adjust Z offset in 0.05 mm increments from the touchscreen during the first layer and watch the change before adjusting again, since the correction has a short delay before it takes effect. If offset correction alone does not fix it, the next step is cleaning the plate, since QIDI notes that grease or residue on a PEI surface is a common secondary cause, and recommends isopropyl alcohol or warm water rather than harsher solvents.
Interface and firmware faults
A known issue on the Plus 4 is the Fluidd web interface failing to render correctly, or loading blank, after a firmware update. QIDI’s fix is not a settings toggle, it requires SSH access to the printer (default credentials mks / makerbase), deleting the existing fluidd folder on the board, and replacing it with a fresh copy pulled from QIDI’s own GitHub repository. This is a file corruption issue tied to the update process rather than a hardware fault, and it does not carry a QDC or QDE code either.
For deeper firmware or boot failures, QIDI’s documented recovery path is reflashing the eMMC storage module entirely using a dedicated Plus 4 system image with balenaEtcher or Rufus, which is the same procedure used for corrupted storage across their Klipper-based lineup. If you need to hand a fault off to QIDI support, the wiki’s export log guide lets you pull klipper.log and moonraker.log either from the touchscreen’s Export Log option or directly from the Fluidd System tab, and that log is what support will actually need to identify a fault QIDI has not documented publicly yet.