The Saturn 4 Ultra does not use numbered fault codes the way some FDM printers do. Instead, its firmware runs a self-test on power-up (and again before each print) and displays a short text message on the touchscreen when something fails, things like “X-axis Motor Status,” “Foreign matter detected, please troubleshoot,” or “Auto-leveling failed, please troubleshoot.” Elegoo’s official wiki documents these messages as individual troubleshooting articles rather than as a single numbered list, so this index is organized the same way: by what the screen actually says and what part of the machine is involved. Several of these pages are shared verbatim across the Mars 5 Ultra, Saturn 4 Ultra, and Saturn 4 Ultra 16K, since the three machines use the same mainboard and self-test logic, and Elegoo’s own guides note that explicitly. The Saturn 4 Ultra is a resin (MSLA) printer with a 10.1-inch 12K mono LCD masking screen and a COB 405nm light source, so its fault categories center on the Z-axis leveling mechanism, the mechanical leveling sensor, the resin vat, and the touchscreen/mainboard, not on extruders or bed thermistors.
Self-test motion and leveling faults
X-axis Motor Status appears after the self-test completes and the X-axis homing (zero-return) move behaves abnormally, usually with an audible impact as the axis hits a limit it should not. Elegoo lists four causes: loose or dislodged fasteners on the X-axis motion assembly, incorrect firmware or a mis-flashed gcode configuration file, a faulty X-axis limit switch, or a damaged X-axis motor. The fix path works through those in order: retighten the motion hardware, confirm the firmware version and reflash if wrong, inspect the limit switch wiring (swapping the X and Z limit switches helps isolate which one is bad), and finally check the motor’s wiring for resin ingress or a short.
Auto-leveling failed shows up during the self-test or mid-print with the message “Auto-leveling failed, please troubleshoot.” Elegoo attributes this to the printer sitting on an unstable or vibrating surface, a build plate that is not fully locked down or has loose mounting screws, a bad cable or adapter board on the mechanical leveling sensor, or an out-of-range detection threshold on that sensor. The fix starts with moving the printer to a stable, vibration-free surface and reseating the build plate, then moves to the sensor cable and adapter board. If that doesn’t resolve it, Elegoo has users run a file called Exporting.gcode from a USB drive, which generates a 100MachineParams.gcode file to send to support along with the resin type and viscosity in use.
Mechanical Sensor Error is a related but separate fault tied to the mechanical leveling sensor itself rather than the leveling result. Causes listed are unstable placement, nearby vibration sources, a loose or damaged sensor cable, a tangled spring wire, or a damaged adapter board. The recommended fix includes placing the printer directly on the floor as a test, since a rigid, low surface removes vibration as a variable. If untangling the spring wire and reseating the cable don’t clear it, Elegoo asks for photos of the wiring, adapter board, and error message before offering a replacement path.
Z-axis motor status (documented under the page title “Motor cannot operate properly”) triggers during the power-on self-test or a manual self-test, and can also show up as the Z-axis making noise, moving incorrectly, or not responding at all when jogged manually. Elegoo lists resin leakage and curing inside the motor housing as the most serious cause, since cured resin can burn out the motor and is treated as a safety issue requiring motor replacement. Other causes include loose mounting screws on the motor or anti-backlash nut, a poor connection at the Z-motor plug, a deformed or under-lubricated lead screw, and a tangled spring cable. The wiki includes a diagnostic swap: disconnecting the X and Z motor connectors and plugging the X-motor into the Z-axis socket, then watching whether the build platform moves during self-test. If it moves, the Z-motor or its cable is at fault; if it stays still, the mainboard needs replacing.
Resin tank and foreign-matter faults
“Foreign matter detected, please troubleshoot” can appear during the pre-print self-check or while a print is running. Elegoo’s list of causes is long: an unstable or vibrating surface, leftover cured resin or print debris in the vat from a failed print, resin curing prematurely from stray light exposure, a build plate that isn’t seated correctly, contamination or burrs on the build plate surface, resin that’s too viscous and triggers a false positive, or a wiring fault between the mechanical sensor and its adapter board. The fix sequence in the wiki works through cleaning the vat and build plate first, avoiding direct sunlight or strong UV near the vat during printing, warming overly viscous resin before use, and checking sensor wiring last. As with the leveling fault, if the problem persists Elegoo wants the same Exporting.gcode-generated parameter file along with the resin details.
Resin Tank Status Failure / “Resin Tank Not Detected” is worth flagging carefully: Elegoo’s own page states this instruction applies only to the Saturn 4 Ultra 16K, not the standard Saturn 4 Ultra. It relates to the 16K’s automated resin dispensing tank, which has physical dispensing tips and contact points that the plain Saturn 4 Ultra’s resin vat does not have. Causes include using an incompatible or wrongly oriented resin tank, damaged or worn dispensing tips, tips obstructed by the release film, poor contact between the adapter board and its contact points, or a broken circuit in the tank itself. Because this fault is specific to the 16K variant, owners of the standard Saturn 4 Ultra should not expect to see this message, and if they do, it likely points to a different underlying issue not covered by this particular guide.
Power-on and touchscreen faults
Touch screen does not turn on after powering the printer covers the case where the machine gets power but the display stays blank. Elegoo lists several possible triggers: a USB drive left inserted before the power switch is flipped on, a failing power adapter, a bad or incompatible firmware flash, a poorly seated touchscreen ribbon cable, or a short circuit somewhere on the board. The troubleshooting sequence starts simple (pull the USB drive, restart) before moving to checking the adapter’s output voltage with a multimeter, reflashing firmware from a specific repair firmware package, and reseating the ribbon cable at both the screen and the mainboard. If none of that works, Elegoo has users disconnect every mainboard connector except the essentials and reconnect them one at a time (LED, X-motor, Z-motor, sensor, temp, camera, fans, LCD) to isolate which component is shorting.
Touch screen stuck at the ELEGOO logo is a different symptom: the screen powers on and shows the boot logo but never reaches the main interface. Elegoo attributes this to a crashed firmware or a short circuit on a connected component. The fix starts with formatting a FAT32 USB drive under 16GB, copying over a fixing firmware file named ChituUpgrade.bin, and letting the printer auto-update on restart. If the logo freeze continues after that, the next step is disconnecting mainboard components (keeping the touchscreen connected) to see if the board itself needs replacing, or whether a specific attached part is causing the short.
File and print-start faults
Print button does nothing even though the USB drive reads correctly is documented under a page that explicitly covers the Mars 5 Ultra, Saturn 4, and Saturn 4 Ultra together. Elegoo lists mismatched printer model settings in the slicer, file corruption during saving or transfer, a sliced file format the machine can’t parse, or firmware that’s incompatible with the model or missing parameters. The wiki’s fix starts in the slicer itself: confirming the correct printer profile is selected (or manually matching the core parameters if no official preset exists), re-slicing the model to rule out geometry errors, and switching to a FAT32-formatted USB drive of 32GB or less rather than NTFS. If the file itself checks out, the last step is restoring factory settings and running an OTA firmware update, or flashing firmware manually via USB if the printer doesn’t support OTA.
The Saturn 4 Ultra shares several of these self-test fault pages verbatim with Elegoo’s Mars 5 Ultra, since both machines use the same mainboard and self-test logic. See the Elegoo Mars 5 Ultra Error Index for how those shared faults are documented on that printer. For the plain, non-Ultra Saturn 4, which lacks the automated resin tank and has thinner official documentation of its own, see the Elegoo Saturn 4 Error Message Index.