Toshiba MMU-P0121H Service Manual page 85

Check code
[AF]
Phase order alarm
There is an abnormal power phase order or mossing a phase of power supply of the outdoor unit.
Modify power supply wiring
Check code
[b4]
Ps sensor alarm
Are Pd sensor/Ps sensor
connectors correctly connected?
YES
Is output voltage characteristics
of Ps sensor normal?
YES
Is low-pressure below 0.95MPa
during operation of compressor?
YES
Check interface P.C. board.
Abnormal power phase order or mossing a phase of power
supply of outdoor unit
1. Ps sensor error
2. Ps sensor connection error
3. Compressor compressing error
4. 4-way valve error
NO
NO
NO
Does refrigerant bypass from
outlet to inlet on 4-way valve?
YES
Check 4-way valve.
3-82
Operation cause
Operation cause
Modify connector connection.
Pd sensor : CN501
Ps sensor : CN500
Sensor error
NO
Check compressor.