GE Microwave Error Code Lower Thermal Sensor SHORTED

This error means the GE microwave's Smart Board has detected a short circuit in the lower thermistor circuit, connected at board connector CN09 via red and white wires. The thermistor normally reads approximately 256K ohms at room temperature, and a shorted condition means resistance has dropped drastically below that value. This is most often caused by a failed thermistor component but can also result from damaged wiring. The microwave will typically stop operating until the fault is resolved.

It is not recommended to use the microwave while this error is present. The lower thermistor is part of the thermal monitoring system that helps prevent overheating. With the sensor shorted, the control board cannot accurately track temperature in the lower cavity, which removes a layer of overheat protection. Most GE microwaves will also disable normal operation when this fault is active.

If only the thermistor needs replacement, parts typically range from around $15 to $50 depending on the specific model, with professional labor adding $75 to $150 or more. If the Smart Board is the root cause, board replacement costs can range from $100 to $250 or higher for parts alone. Getting a diagnosis first will help determine whether repair is cost-effective compared to replacing the microwave.

Simply resetting or unplugging the microwave will not clear this error permanently because it is caused by a hardware fault, not a temporary software glitch. The Smart Board will re-detect the shorted thermistor circuit as soon as it powers up and runs its self-check. The underlying cause, whether a failed thermistor or damaged wiring, must be repaired before the error will stay cleared.

Start by disconnecting power and accessing the lower thermistor, then measure its resistance across the red and white leads at Smart Board connector CN09. If the reading is near zero ohms rather than the expected 256K ohms at room temperature, the thermistor needs to be replaced. Also inspect the wiring harness for any chafed, pinched, or burned insulation that could be causing the short before the signal reaches the board. If both the sensor and wiring check out, the Smart Board may need to be evaluated.