Neptune 4: Klipper motor error («TMC stepper… reports error», «No trigger on x…»)

Symptom

The Neptune 4 or 4 Pro screen (or Fluidd) shows a motor error at power-on, when homing or while printing, and the printer stops. For example, a «TMC stepper_y» error with «otpw=1(OvertempWarning!)» (overtemperature warning), «TMC stepper_z reports error» with «s2vsa=1», «Unable to read tmc uart 'stepper_y' register IFCNT» or «No trigger on x after full movement».

Likely causes, from most to least likely

1. The motor connector is loose, on the motor side or on the mainboard (under the bottom cover).
2. The motor overheats or is overloaded: the fan under the base is not spinning (it starts once the nozzle passes 50 °C, according to Elegoo) or the X/Y belts are too tight.
3. The motor current was changed or the Klipper configuration was edited incorrectly.
4. A motor or its cable is faulty; the Z axis has two motors and one of them may fail.
5. The motor driver on the mainboard is faulty.

Checks to tell which one it is

• Note the axis (x, y or z) and the exact error text.
• With the nozzle above 50 °C, check whether the fan under the base is spinning.
• Swap the X and Y motors (their connectors on the mainboard, or the motors themselves, as Elegoo's guide describes): if the error stays on the same axis, it points to the mainboard or the cable; if it moves to the other axis, to the motor or its cable.
• On the Z axis, disconnect one of the two motors and move Z: if the error disappears, the disconnected motor is the faulty one.

Before you start

Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.

Step-by-step fix

1. Reseat the motor connector

   Switch the printer off and unplug the power cable. Unplug and firmly reconnect the motor connector of the axis giving the error, at the motor and on the mainboard. To reach the board, remove the bottom cover screws; a cable joins the cover to the board and must be disconnected before moving the cover away.

   Check: After switching on and homing, the error does not return.

   If that does not fix it: Check the fan and the belts (next step).

2. Base fan and belts (overtemperature)

   If the error is an overtemperature warning (otpw), heat the nozzle above 50 °C and check that the fan under the base spins; if not, with the printer off open the bottom cover and remove whatever is blocking it. Loosen the X/Y belts slightly by turning their tensioner anticlockwise: an overtight belt overloads the motor.

   Check: The fan spins and the overtemperature warning does not return during printing.

   If that does not fix it: Restore the firmware (next step).

3. Restore the original firmware

   If you changed the motor current or edited the configuration, reinstall Elegoo's official firmware (fix pack, mainboard firmware and screen firmware) to get the factory values back.

   Check: With the original configuration, the error disappears.

   If that does not fix it: Isolate the faulty part (next step).

4. Find out whether the motor or the board is faulty

   With the printer off and unplugged, swap the X and Y motor connectors on the mainboard and try homing. On the Z axis, disconnect one of the two motors, switch on and move Z with Prepare → Z+ (before homing it can only move up).

   Check: If the error moves to the other axis, the motor or its cable is faulty; if it stays on the same axis, the mainboard or the cable. On Z, if it disappears with one motor disconnected, that motor is the faulty one.

   If that does not fix it: Ask Elegoo technical support for the spare part (motor, cable or mainboard); according to Elegoo, these checks do not void the warranty.

Prevention

• Do not change the motor current or the Klipper configuration unless you know how to go back to the factory settings.
• Keep the base fan clear and do not overtighten the belts.

Still not fixed?

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Printers it applies to

Elegoo Neptune 4 and Neptune 4 Pro.

Official sources

This guide summarises the official documentation linked here:

• Neptune 4/4 Pro TMC stepper_y reports error: DRV STATUS: 401b0103 otpw=1 (OvertempWarning) · Elegoo
• Neptune 4 & 4 Pro error: No trigger on x after full movement · Elegoo
• Neptune 4 Series Error: Unable to read tmc uart stepper_y register IFCNT · Elegoo
• Neptune 4 & 4 Pro Error Reported: TMC stepper_z reports error (LowSideShort_A) · Elegoo