Sovol’s official error-code page for the SV08 documents four numbered codes: 8, 21, 3 and 26. All four are readable either on the knob screen or in the Mainsail web interface, reachable over the printer’s WiFi connection.
Error 8 is an umbrella for several distinct messages Mainsail can surface, and it’s the one you’ll run into most. A nozzle-adapter-board communication problem falls under it: check the adapter board’s connections and cable, and look for a lit red indicator light to report to Sovol. The same code covers “Lost communication with MCU ‘extra_mcu’” (check the adapter board wiring; if the message reads “Can not update MCU ‘extra_mcu’ config,” a Klipper restart or power cycle usually clears it without harm), an “ADC out of range” thermistor fault (checked against the nozzle thermistor reading in Mainsail), a nozzle or bed heater not reaching temperature at the expected rate (tested by setting 200C for the nozzle or 65C for the bed on the knob screen and watching whether it climbs), TMC driver errors naming a specific motor, Z1 through Z4, X or Y, and an “Exception in Fan” message pointing at the Fan1 or Fan2 wiring on the adapter board.
Error 21 turns up during a print and points at the heated bed’s internal wiring. Error 26 means the bed thermistor is reporting a reading that’s negative or implausibly high, checked the same way as the nozzle ADC fault, by watching the bed thermistor value in Mainsail. Error 3 is the vaguest of the four. Sovol doesn’t tie it to one specific root cause, and its documented fix leans entirely on exporting a Mainsail log and reflashing firmware if that doesn’t help.
The same pattern runs through all four codes: check a specific reading or connection first, and if that doesn’t resolve it, export a log from Mainsail for Sovol to look at. Sovol also keeps a separate, unnumbered troubleshooting index for symptoms outside these four, covering things like axis noise or a stuck screen. Worth a look if what you’re seeing doesn’t match any code here.
Most SV08 error codes trace back to a specific reading or connection covered in the SV08 calibration guide, particularly the two probe-related faults that can interrupt a leveling pass. Routine care from the SV08 maintenance schedule helps prevent several of these from coming up in the first place, and for troubleshooting that isn’t printer-specific, the first-layer troubleshooting guide is a useful general reference. Note that the SV08’s Klipper-based error codes above are specific to this CoreXY machine and don’t carry over to the Marlin-based Sovol SV06, which shows plain firmware text instead of numbered codes. A third sibling, the Sovol SV07, also runs Klipper but without the SV08’s numbered code set, reporting faults as plain Klipper shutdown text instead.