The “TMC Extruder…lowside short” error causes Klipper to halt the Elegoo Neptune 4 Plus or Neptune 4 Max immediately. This fault indicates that the stepper motor driver (TMC chip) controlling the extruder has detected a short circuit on its low-side output, which is an electrical safety shutdown designed to protect the driver and motor from damage.

What the Error Means

TMC stepper drivers continuously monitor the current through each motor winding. A lowside short occurs when the driver detects a current path that bypasses the motor winding — essentially an electrical short on the output stage. On the Neptune 4 Plus and Max, the most common hardware cause is a loose, bent, or damaged connector on the extruder motor cable. Damaged cable insulation that allows two conductors to touch, or a failing extruder controller board with a damaged TMC chip, are less common but possible causes. This error is specific to the Neptune 4 Plus and Max; the base Neptune 4 and Neptune 4 Pro use a different extruder architecture and are not typically affected by this specific fault code.

Step-by-Step Fix

1. Power off the printer immediately when this error appears. Running a motor with a short in the driver circuit can permanently damage the TMC chip or the motor windings.
2. Locate the extruder motor cable connector. On the Neptune 4 Plus and Max, refer to the ELEGOO Wiki diagram for the exact connector position on the extruder controller board — the connector is labeled in the diagram for that model.
3. Inspect the connector plug for physical damage: loose retention clips, bent or pushed-back pins, or corrosion on the contacts. A misaligned connector is the most common cause and the easiest to fix.
4. Disconnect and firmly re-seat the extruder motor cable connector at both the motor end and the controller board end. Ensure it is fully and squarely engaged.
5. Trace the extruder cable along its full routed length, looking for cuts in the insulation, tight bends that could have caused internal wire breaks, or areas where two conductors may be touching. Replace the cable if any damage is found.
6. Restore power and run a short extrusion command (5–10 mm at low speed) to test. If Klipper does not shut down, the short is resolved.
7. If the error returns immediately after re-seating and the cable is undamaged, the extruder controller board (breakout board) has likely failed. If the printer is within warranty, apply for a replacement breakout board, proximity switch, and extruder cable through ELEGOO support.

Parts Required

• Replacement extruder motor cable (if cable insulation is damaged)
• Replacement extruder breakout/controller board (if board-level TMC failure is confirmed)
• Proximity switch (supplied with replacement board kit per ELEGOO support process)

Contact ELEGOO support for warranty replacement of the breakout board and cable assembly if the short persists after reseating all connectors and confirming the cable is undamaged.

Frequently asked questions

What does Elegoo n4-tmc-extruder-short mean?

The "TMC Extruder...lowside short" error causes Klipper to halt the Elegoo Neptune 4 Plus or Neptune 4 Max immediately. This fault indicates that the stepper motor driver (TMC chip) controlling the extruder has detected a short circuit on its low-side output, which is an electrical safety shutdown designed to protect the driver and motor from damage.

How do I fix Elegoo n4-tmc-extruder-short?

Klipper's TMC extruder lowside short error halts the Neptune 4 Plus and Max. Learn how to identify and fix the short in the extruder stepper driver circuit.