Safety first: Turn off power at the breaker and verify the oven is de-energized before testing.

Inspect wiring: Access the rear of the oven and trace the sensor wires from the cavity to the control board. Look for crushed insulation where the harness passes through metal panels.
Disconnect and test sensor: Unplug the sensor from the harness and measure resistance. A reading near 0 Ω indicates a shorted sensor; replace it.
Check for moisture: If the connector area is damp (from steam or cleaning), dry thoroughly and allow time before retesting.
Harness isolation: If the sensor tests normal, inspect the harness for points where wires may be touching the metal chassis. Repair or replace damaged sections.
Control board replacement: If sensor and harness are good but F4 persists, the control board sensor circuit is likely shorted internally and the board must be replaced.

Warning: Do not operate the oven with a known sensor fault; it may overheat and pose a fire risk.

F4 displayed; oven may overheat or show erratic temperature behavior

Possible Causes