Microwave runs but does not heat; display shows E03 after a few seconds.

Critical safety warning: The high-voltage section (transformer, capacitor, diode, magnetron) can store lethal voltage even when unplugged. Do not attempt internal repairs unless you are a trained appliance technician with proper tools and procedures.

User-level checks:

• 1. Confirm symptom: Place a cup of water in the oven and run for 1–2 minutes. If the turntable rotates and the light is on but the water remains cold and E03 appears, the high-voltage system is likely at fault.
• 2. Check power supply: Plug the microwave directly into a wall outlet (no extension cord or power strip). Low voltage can sometimes trigger HV errors.
• 3. Reset the unit: Unplug for 5 minutes, then plug back in and test again. If E03 reappears, internal components need diagnosis.

Technician-level actions (for professionals only): Test the high-voltage transformer windings, discharge and test the HV capacitor, check the HV diode for shorts/opens, and verify magnetron continuity and insulation. Replace any failed component with Toshiba-compatible parts.

Recommendation: Due to shock risk and specialized tools required, contact an authorized Toshiba service center for E03 faults.