York HP Series Service Manual page 95

16.4.2 Communication malfunction between indoor and outdoor units diagnosis and solution
(E1)
For 9K-24K:
Error Code
Malfunction conditions
Potential causes
Trouble shooting:
E1
If the indoor unit does not receive feedback from outdoor unit for
110 seconds 4 consecutive times.
Wiring mistake
●
Faulty indoor or outdoor PCB
●
92