The plate HX is freezing — the manual's leading causes are reduced water flow (clogged filter, leakage, air) and LEV faults.
Safety: If the plate has frozen, do NOT restart until water flow is proven — a burst plate dumps refrigerant into the water circuit.
How to read it — ftc controller: Ecodan check codes show on the FTC / main controller display. (Ecodan service manual OCH727, §9-2 self-diagnosis action table)
UK models this code applies to
From the Mitsubishi Electric service literature we hold (Ecodan service manual OCH727 §9-2) — not a scraped list.
P6 names a symptom, not a root cause. In the app, the same code opens a guided investigation: what to measure first, the expected values for your exact model, and an honest verdict — including “nothing in this machine is broken” when that's what the readings say.