LG range shows F4 and oven may not heat correctly or may shut off.

Safety first: Turn off power at the breaker. Allow the oven to cool.

• Inspect sensor wiring: Remove the rear panel and visually inspect the sensor harness from the sensor probe to the control board. Look for areas where the insulation is crushed, melted, or touching metal.
• Test resistance: Disconnect the sensor at the harness and measure resistance. At room temperature, it should be ~1080 Ω. A very low reading (e.g., <500 Ω) indicates a shorted sensor.
• Check harness to chassis: With the sensor disconnected, measure resistance from each sensor wire to chassis ground. Any low reading indicates a short to ground in the harness; repair or replace the harness.
• Replace sensor if needed: If the sensor is shorted, install a new LG oven temperature sensor and secure it properly.
• Control board check: If sensor and harness are good but F4 persists, the control board sensor input may be shorted internally and the board will need replacement.