LG inverter split AC light blinking in 21 time

#LG split inverter AC #bcpboard error # LED red light blinking
LG inverter split AC outdoor PCB board light blinking 21 time what reason?
hecks for the CH21 errorComponentsOutdoor unit checks
Check the power at the disconnect
Check the outdoor unit’s power supply
Check the ODU bridge diode
Noise filter and compressor component checks
Check the noise filter power supply
Check the compressor terminals for tightness
Check the resistance of compressor windings
Check the compressor windings to ground
Inverter checks
Check the inverter IPM
Check the inverter PCB