The symptom pattern

Mid-print, or sometimes at the moment heating is commanded, the Ender 3 V2 stops and puts Err: MINTEMP on the screen, usually alongside Printer halted. kill() called!. Everything locks up: the controls do nothing, the heaters go off, and only a power cycle brings it back. Sometimes it prints fine afterwards for a week. Sometimes it fails again within minutes, and increasingly often as time goes on.

That pattern — intermittent at first, then more frequent — is characteristic, and it points at a specific kind of failure.

What’s actually happening

MINTEMP is not a fault report. It is a safety cut-out doing its job.

Marlin, the firmware family the Ender 3 V2 runs, compares each thermistor’s reading against a configured minimum. If the temperature comes back below that floor, the firmware concludes the reading cannot be trusted and halts the machine rather than continue driving a heater blind. The default minimum is 5 °C. A working thermistor in a normal room reads well above that, so in practice a MINTEMP means the temperature-sensor circuit has gone open — the board is reading, in effect, nothing at all.

Open circuits in this position are usually mechanical. The hotend loom on a bedslinger moves thousands of times a print, and copper work-hardens where it flexes. A strand parts, then another, and the connection becomes marginal before it becomes permanent — which is exactly why the fault starts as an occasional halt and becomes a reliable one. Connectors that have worked loose, and crimps that have gone brittle from sitting near the heater block, produce the same picture.

There is one honest exception. If the printer lives in an unheated UK garage in winter and the ambient really is below the configured floor, MINTEMP can trigger with absolutely nothing wrong. It is worth ten seconds of thought before it is worth an hour of dismantling.

Working through it

Use the reported temperature as your test instrument. Power on, command no heat, and flex the loom by hand while watching the number on the display. Nothing is hot, nothing is moving under power, and a healthy circuit holds a steady reading through the full range of movement. A reading that drops to zero as you bend a particular spot has told you where the break is.

If that comes back clean, unplug and work the connectors — both ends, hotend and mainboard — and inspect the crimps properly under a light. Then measure: around 100 kΩ at room temperature for a healthy 100 kΩ NTC, open circuit for a dead one.

What not to do is edit the threshold out. It is tempting when a message keeps stopping a long print, and it removes the only thing standing between a broken sensor and an unmonitored heater.

Verdict

A cheap fix with a scary message attached. Cold ambient and a loose connector cost nothing to rule out; beyond that, a replacement cartridge thermistor is a couple of pounds and a short job with a hex key. Nothing about a MINTEMP suggests the printer is finished — it suggests the printer noticed.