Diagnosis
The oven temperature sensor is giving incorrect readings to the control board. This is a calibration issue.
How to Fix It
First, test the actual temperature. Use a standalone oven thermometer. Preheat to 350°F and let it cycle for 20 minutes. Note the difference. You can recalibrate the oven. Press and hold the "Bake" button for 6 seconds until the display shows "CAL". Use the up/down arrows to adjust the offset in 10-degree increments. If your thermometer reads 340°F, increase calibration by +10. Press "Start" to save. Re-test.
If That Didn't Work
If calibration can't correct a large offset (over 50°F), the sensor itself is bad. Replace the oven temperature sensor (part 5304518479). Unplug range, remove back oven interior panel, disconnect old sensor, install new one.
Heads Up
All ovens have hot spots. Place the thermometer in the center of the middle rack for the most accurate test. Avoid calibrating based on one test; verify with a second run.