Toshiba HWT-601XWHM3W-ETR Service Manual page 109

[A03] Temperature increase error (hot water supply)
Start
TTW sensor
characteristic is correct
Hot water cylinder heater
is energized
At normal
temperature, tank thermostat
is energized
Hot water cylinder
thermostat operates
Check water heat exchange control board
(TTW ≥ 85°C is detected)
No
Yes
No
Yes
No
Yes
No
Operation
temperature 82°C
Yes
If defective, replace it
PC board
MCC-1753
MCC-1755
108
Replace TTW sensor
Replace hot water
cylinder thermostat