The 2 most common part(s) or condition(s) which cause the symptom Oven won't turn off are listed below starting with the most likely. Check or test each item and watch any available videos.
RepairClinic Item # 1086191
The oven control board has a set of relays that turn on and off power to the bake and broil circuits according to the customer settings and sensor input. If the oven won't turn off it could be that one of the relays on the oven control board is shorted closed, providing voltage to the heating circuit. It can be dangerous if the oven won't turn off. Don't leave the oven unattended without turning off power to the oven.
RepairClinic Item # 251863
If the oven won't turn off the oven thermostat is often the cause of the problem. Sometimes the electrical contacts inside the oven thermostat weld themselves together and then the oven won't turn off. If this happens, turn off power to the entire appliance at the household circuit breaker or fuse. The oven thermostat usually cannot be tested and must be replaced if defective.