Crash Detected
Prusa 3D Printer
Severity: ModerateWhat Does This Error Mean?
Crash Detected means a stepper motor encountered unexpected resistance — the print head hit something. The printer uses sensorless homing (Trinamic drivers) to detect this. Check for obstructions, loose belts, or a print that curled up and hit the nozzle.
Affected Models
- Prusa MK4
- Prusa MK3S+
- Prusa XL
Common Causes
- Print warped and curled up, hitting the nozzle during travel
- Foreign object on the bed or in the print area
- Axis belt too loose — motor skipping steps
- Crash detection sensitivity too high
- Print head cable snagging
How to Fix It
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Check for a warped print or obstruction.
If the print curled up and hit the nozzle, the crash was real. Remove the print, fix adhesion, and restart.
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Check belt tension.
Loose belts cause the crash detection to trigger during normal fast moves. Tighten belts until they are taut.
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Enable Z-hop in PrusaSlicer to avoid nozzle-print collisions.
Z-hop lifts the nozzle during travel moves. Print Settings > Travel > Lift Z.
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Adjust crash detection sensitivity.
LCD > Settings > Crash detection > sensitivity. Lowering sensitivity reduces false positives but may miss real crashes.
Frequently Asked Questions
Can the printer recover from a crash?
Yes. Prusa's crash recovery re-homes the axes and continues printing from where it stopped. The success depends on how much the print shifted during the crash.
What is sensorless homing?
Trinamic stepper drivers can detect when a motor hits an obstacle by measuring electrical current changes. This eliminates the need for physical endstop switches.