Frigidaire Refrigerator Error Code I/M-SENSOR

The I/M-SENSOR error code on a Frigidaire refrigerator indicates a fault within the ice maker temperature sensor circuit. This sensor is a thermistor that feeds real-time temperature data to the main PCB, allowing the control board to regulate ice production cycles. The error triggers when the sensor signal falls outside the expected voltage window at the main PCB sensor connector, specifically below 1.0V or above 4.5V, or when the corresponding temperature reading exceeds 122°F or drops below -58°F. Both open-circuit and short-circuit conditions in the sensor wiring will push the voltage outside this range and trigger the fault.

The thermistor operates as a resistive temperature device, meaning its resistance changes predictably with temperature. The main PCB applies a reference voltage across the sensor circuit and reads the resulting signal voltage to calculate ice maker compartment temperature. When the circuit is broken (open) or shorted, the voltage collapses to near zero or climbs toward the supply rail, both of which fall outside the 1.0V to 4.5V valid operating window. Connector failures are a frequent culprit, as corrosion or loose pins at the harness connector can intermittently interrupt the signal path and mimic an open-circuit fault.

Diagnosis should begin at the main PCB sensor connector by probing the voltage between the sensor signal and ground terminals. A reading outside the 1.0V to 4.5V range confirms the fault is active. From there, technicians should inspect the wiring harness for chafing, pinching, or moisture intrusion, and test the thermistor resistance directly at the sensor body to distinguish a failed sensor from a wiring or connector problem.