Maytag Refrigerator Error Code OP

The OP error code on a Maytag refrigerator indicates that the control board has detected an open thermistor or an open circuit condition during normal operation or a service test. A thermistor is a temperature-sensing resistor whose resistance value changes predictably with temperature. When the control board reads a resistance value that falls outside the expected range, or detects no signal at all from the thermistor circuit, it registers the OP code and flags the sensor as non-functional. This can affect the fresh food compartment, freezer, evaporator, or ambient thermistor depending on which circuit is open.

For homeowners, think of the thermistor as the refrigerator's thermometer. It constantly reports temperatures back to the main control board so the compressor and fans cycle on and off at the right times. When this sensor circuit breaks or loses continuity, the board has no reliable temperature data to work with. This means cooling may become erratic or stop entirely because the board cannot make accurate decisions about when to run the compressor.

The code can be triggered by a physically failed thermistor, a broken or corroded wire in the harness leading to the sensor, or a loose connector at either the thermistor or the control board. Running the refrigerator's service test mode will isolate which thermistor circuit is reporting the open condition, which is the first step toward a targeted repair.