Microwave displays E4 and will not start; sometimes appears immediately when plugging in.

Safety: Disconnect power before opening the cabinet. Avoid contact with high-voltage components. If unsure, hire a technician.

Steps to troubleshoot E4 temperature sensor error:

• 1. Power cycle: Unplug for 5–10 minutes, then reconnect. If E4 reappears, proceed.
• 2. Locate the temperature sensor: Remove the outer cabinet. The NTC sensor is typically mounted on the cavity wall or near the top of the oven cavity, connected by two small wires to the control board.
• 3. Inspect the sensor and wiring: Check for broken insulation, burnt spots, or a sensor that has fallen away from its mounting clip. Reseat or reclip if loose.
• 4. Test the sensor: Disconnect the sensor from the harness. Measure resistance with a multimeter at room temperature. Compare to Galanz service specs (commonly in the 50–300 kΩ range depending on design). If reading is open, shorted, or far out of spec, replace the sensor.
• 5. Check harness and board: If the sensor tests good, inspect the harness for continuity from sensor connector to the control board. If wiring is good, the control PCB sensor circuit may be defective and require replacement.