Hi everyone,
I swapped the hotend on my Ender‑3 V3 KE because of sensor temperature errors, and ever since then the printer refuses to finish its startup diagnostics. I’ve gone through all the usual steps, but it’s stuck in a loop and never reaches the main menu.
What happens:
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On every boot I get “Machine diagnostics in progress”
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Instead of the main menu, it drops into the temperature graph
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The Home button doesn’t work
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Movement/Extrude opens, but Home just loops back
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After a bit, the screen goes black
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Firmware update from USB doesn’t trigger
What I’ve already tried:
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Reseated all connectors (ribbon cable, thermistor, heater cartridge, probe, Z‑endstop, display cable)
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Checked for bent pins
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Verified the heater block is properly seated (KE model)
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Cold‑booted multiple times
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Tried firmware reflash (printer doesn’t detect it)
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Reran diagnostics from Settings (same result)
Temps read normally (30–55°C depending on how long it’s been on), but they don’t rise, so the heaters aren’t being activated.
At this point I’m thinking a hardware component isn’t being detected — maybe the extruder adapter board, ribbon cable, thermistor, probe, or even the mainboard.
If it helps, I can attach 2–3 photos (extruder adapter board, ribbon cable seating, and the diagnostic/temp screens).
Has anyone run into this exact behavior or found a fix?
Thanks, Robert