Yes
Yes
Measure  Vs, is it moving alternately 
with positive value?
(Vs is the voltage between L2 and S 
of outdoor unit. Connect the red pin of 
multimeter with L2 port, black pin with 
S port)
Yes
Power off, then turn on the unit 5 seconds 
later(reconnect the power wire).Is the error 
still displaying after several minutes?
No
Replace the outdoor main PCB.
Power on. Is the error extinguished?
Check all the wiring with indoor units. 
Is the wiring to the indoor main PCB 
connected correctly? 
Replace the indoor main PCB.
Yes
Replace the outdoor main PCB.
No
Check all the wiring with outdoor 
u ni t s.   Is the  wiring  to the outdoor 
main PCB connected correctly? Is 
the reactor connected well?
Power on. Is the error extinguished?
Replace the indoor main PCB.
No
Yes
Measure the resistance of the 
reactor(The one without capacitor). 
If it is zero ,follow the below step. If 
not, replace a new reactor.