LG Heat Pump Error Code E551

E551 on an LG heat pump is an informational status code indicating the unit is performing an automatic defrost cycle. It is not an error or a fault. The system is melting frost that has accumulated on the outdoor coil, and normal heating operation will resume automatically once the cycle completes.

Yes, it is completely safe. E551 indicates a normal, designed function of the heat pump. The system is managing itself correctly to protect the outdoor coil and maintain efficiency. You do not need to turn the unit off during a defrost cycle.

If E551 appears occasionally during cold weather, there is no repair needed and no cost involved. If the code appears frequently due to a low refrigerant charge, expect refrigerant diagnosis and recharge costs in the range of $150 to $400 depending on the refrigerant type and amount needed. A defrost sensor or control board replacement, if required, could range from $100 to $500 or more in parts and labor.

In most cases, no action is required. The defrost cycle runs automatically and clears on its own, typically within 5 to 15 minutes. You should check that the outdoor unit is free of debris, snow, or ice blockages that could be contributing to frequent defrost events. If E551 displays for longer than 20 to 30 minutes repeatedly, contact a qualified technician to inspect the system.

Resetting the unit is not necessary and will not speed up the defrost process. The E551 status clears automatically once the control board determines the outdoor coil has reached its defrost termination temperature and returns to heating mode. Powering the unit off and on during a defrost cycle may simply restart the process from the beginning.