Hitachi Yutaki M & Yutaki S fault codes

40 codes from the Hitachi manual for the Yutaki M & Yutaki S heat pump. Pick one for what it means, the likely causes and where to start.

Code	What it means
03	Lost communication with all sub YUTAKI units
10	Indoor 2nd DHW thermistor anomaly
100	Indoor-LCD compressor protection
106	Excessively high discharge gas temperature
12	Indoor water outlet thermistor abnormally (THMwo)
15	Water circuit 2 thermistor abnormally (THMwo2)
16	Water DHW thermistor abnormally (THMdhwt)
17	Auxiliary sensor 2 thermistor abnormally (THMaux2)
18	Auxiliary sensor 1 thermistor abnormally (THMaux1)
19	Activation of the protection device for the indoor fan motor
2	Activation of protection device (high pressure cut)
203	Sub PC-ARFH2E stops answering to main PC-ARFH2E
204	Indoor unit stops answering to main PC-ARFH2E
209	Sub DHW configured on unexisting module
21X	Module X is in alarm state (sub unit)
22	Thermistor for outdoor ambient temperature (THM7)
25	Auxiliary sensor 3 thermistor abnormally (THMaux3)
3	Abnormal transmission between outdoor and indoor units
31	Incorrect capacity setting or combined capacity between outdoor and indoor units
35	Incorrect indoor unit number setting
38	Abnormality of picking up circuit for protection (outdoor unit)
4	Abnormal transmission between inverter PCB and RASC unit PCB
40	Incorrect LCD setting
48	Activation of overcurrent protection
5	Reception of abnormal operation code for detection of power source phase
51	Abnormal operation of the current sensor
6	Excessively low voltage or excessively high voltage for the inverter
60	All sub units are in alarm state or no communication
61	No YCC messages received for more than 180 seconds
62	Central mismatch
63	Transmission error between central and indoor communication
7	Decrease in discharge gas superheat
70	Hydraulic alarm flow & water pump malfunction
75	Freeze protection by cold water inlet, outlet temperature detection
77	Indoor-LCD receiver communication failure
78	Indoor-LCD RF communication failure
8	Excessively high discharge gas temperature at the top of compressor
80	Indoor LCD H-link RCS transmission error
85	Float switch alarm
EE	Compressor protection