Boiler-circuit thermistor open (≤ −40 °C) or short (≥ 140 °C) on hybrid installations.
Safety: Safe isolation before disconnecting sensors or working on the PCB.
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 FTC service manual, error-code chapter + §10-6 thermistor tables) — not a scraped list.
LD 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.