LG Refrigerator Error Code d1

The d1 error code on an LG refrigerator indicates a fault with the upper compartment defrost sensor. This sensor monitors temperature during the defrost cycle in the upper section of the refrigerator. When the control board detects that the sensor circuit is either open (disconnected) or shorted, it triggers the d1 code and may interrupt normal defrost operation. The defrost sensor is a thermistor, meaning its resistance changes predictably with temperature, and the control board uses that resistance reading to determine whether defrosting is complete.

The two core failure modes are an open circuit and a short circuit. An open circuit occurs when the sensor wiring is broken, a connector is loose or corroded, or the thermistor itself has failed internally. A shorted circuit occurs when the sensor wires contact each other or a grounded surface, or when the thermistor collapses to near-zero resistance. In either case, the resistance reading falls outside the expected range for normal operating temperatures, and the board flags the fault.

The first diagnostic step is to inspect the wiring and connectors associated with the upper compartment defrost sensor. Look for damaged insulation, pinched wires, corroded terminals, or disconnected plugs. If the wiring appears intact, the thermistor itself should be tested with a multimeter. A failed thermistor will typically read either infinite resistance or near-zero resistance at room temperature, both of which are outside normal operating parameters. Replacing the faulty component, whether the sensor or the associated wiring harness, should clear the fault.