Diagnosis
The humidity sensor is being triggered prematurely. This is caused by excess ambient steam not coming from the food itself, or using the wrong cookware.
How to Fix It
Follow the sensor cook protocol precisely. Use only microwave-safe containers that are wider than they are tall. Cover the food with a vented lid or wax paper, not plastic wrap which traps too much steam. The initial steam burst must come from the food, not from water left on the container's exterior or from an overly wet surface. Always select the correct sensor program (e.g., 'Sensor Reheat', 'Sensor Cook Vegetables').
If That Didn't Work
The humidity sensor itself, located behind the control panel, may be contaminated or faulty. It can be affected by splatter or grease over time. This requires disassembly for inspection and likely sensor replacement.
Heads Up
The sensor measures humidity, not temperature. Dense foods like casseroles or meats with low initial moisture may not generate enough steam early in the cycle to be sensed correctly. For these, use manual time/power settings.