Panasonic CS-S9PKR Service Manual page 82

14.4.20 H99 (Indoor Freeze Prevention Protection: Cooling or Soft Dry)
Malfunction Decision Conditions

Freeze prevention control takes place (when indoor pipe temperature is lower than 2°C)
Malfunction Caused

Clogged air filter of the indoor unit

Dust accumulation on the indoor unit heat exchanger

Air short circuit

Detection error due to faulty indoor pipe temperature sensor

Detection error due to faulty indoor unit PCB
Troubleshooting
82