The symptom pattern

The printer is powered on and sitting idle, but something in the toolhead-to-display link has gone quiet. It shows up one of three ways: the toolhead won’t respond to the direction buttons on screen, the nozzle and bed temperatures both sit at 0°C with no reading at all, or both of those happen at once.

What’s actually happening

The P1P splits its brain in two: an MC board that drives the toolhead and reads its sensors, and an AP board that runs the screen and talks to the MC board over a dedicated cable. Bambu’s own name for this is an “Rx exception” (the toolhead doesn’t receive movement commands) or a “Tx exception” (temperature data isn’t being sent back) — and which one you’ve got narrows down where to look first.

Safety note, because this involves opening the printer: Bambu’s own guide is explicit that the printer should be powered off and unplugged before any of the teardown steps below — reconnecting a cable or board with power still applied risks a short circuit and further electronic damage.

Working through it

Start by confirming exactly which symptom you’ve got: toolhead movement, temperature, or both. That decides the branch.

If both are affected, leave the printer on and look at the MC board’s status LED through the excess-filament chute — the rear panel comes off if you can’t see it clearly. A normally flashing LED tells you the board itself is alive and the fault is somewhere in the link downstream; replace the MC board only if the LED isn’t flashing at all.

If only temperature is affected, power the printer on, release the tape holding the AP-MC cable in place, and flex the cable gently while watching the displayed temperature. If the reading changes as you move the cable, that’s a loose connection, not a dead part — reseating it is the fix.

If neither of those settles it, work through the rest in order: open the AP board (foam cover off, camera cable disconnected) and look for anything visibly missing or burnt before blaming it; check both ends of the MC-AP cable’s connectors for bent pins or damage; then test the cable itself with a multimeter across the two relevant contact pairs on the AP-side plug — a break in either pair confirms the cable has failed.

If the cable passes and the MC board’s LED was already confirmed healthy, the last step is a visual check of the MC board itself for damaged components.

Verdict

Diagnose before you order anything — the three possible causes here span a huge price range, from a cable that just needed pushing back in, to a cable that needs replacing, to a board that does. Bambu’s own order exists to stop you replacing the expensive part first on a guess. If every check comes back clean — cable intact, both boards undamaged, LED behaving normally — that’s not a sign to keep disassembling further; it’s the point where Bambu’s guide itself hands off to a support ticket with the printer’s log file, because the remaining possibilities need their diagnostic tools, not yours.