[120] Power supply of transducer abnormal
[121] Power supply of inverter board is abnormal
Check if voltage of power supply is normal
Check if wire of electric box is correct
If relay or AC contactor acts well
Measure if DC bus line 
voltage between P and N on 
module is less than 140V
Check rectier, reactor, 
electrolytic capacitor in 
inverter main circuit
DC bus line voltage circuit on 
inverter board broken down, 
replace inverter module board
Adjust or replace relay 
or AC contactor
Correct the wiring due to diagram
Improve power supply circuit
Yes
Yes
Yes
Yes
No
No
No
No
No
Check if voltage of power supply on 
inverter control board is normal
Check if wire between control PCB 
and inverter board is abnormal
If circuit of inverter control board is abnormal
Solve the failures due to relative information
Improve power supply circuit
Adjust communication wire
Replace power module
Yes
Yes
Yes
Yes
No