E1 or CH02 occurs due to short or open circuit in the indoor pipe sensor and is known as an auto-stop protection fault. Not unlikely, the indoor pipe sensor needs to be replaced. Please, disconnect the sensor from the PCB a check resistance. The air sensor should show 10kOhm (25°C), the pipe sensor – 5 kOhm (25°C). If a sensor show resistance levels different from these, replace it.