Easy way to test the thermistor (sensor) in LG (and most other brand) refrigerators
If your heater showed continuity and you did not see any change in sensor, Change sensor. They are quite inexpensive. Good way to test sensor is place in a cup of ice water (mostly ice as you want 32 degrees), leave it in water for 5 minutes...you should get 16k ohms +-5%.
Source: LG refrigerator error code ER-DH