Toshiba 04 fault code

What it means

Block 01 (serial signal / connecting cable). Miswired or defective interconnect, no operation signal from the indoor unit, or no return signal from the outdoor unit. The indoor unit runs on; the outdoor stops.

Safety: Safe isolation before opening terminal covers — mains present on the interconnect.

Source: Toshiba service manual SVM-19001-3 (Seiya) / SVM-20015-4 (Shorai Edge) §11-4, Table 11-4-1

UK models this code applies to

Tap yours to open 04 on that machine.

04 on these comes from each model's own manual, which may not match the meaning above — tap yours to read it.

Now the harder half: proving what caused it

04 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.

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