Oven displays E4 and may not start; often associated with power supply issues.

Safety first: Turn off power at the breaker. Working on mains connections can be lethal; if you are not experienced with electrical systems, contact a qualified electrician.

Step-by-step checks:

• Verify supply voltage: Have a qualified person measure the voltage at the wall outlet or junction box. Confirm it matches the oven's rating (e.g., 220–240V).
• Inspect terminal block: Remove the rear cover to access the power terminal block. Check for loose screws, burnt insulation, or discoloration.
• Tighten connections: With power off, tighten all terminal screws to manufacturer torque specs. Replace any burnt lugs or wires.
• Check power cord: For freestanding models, inspect the cord for cuts, burns, or kinks. Replace if damaged.

When to replace parts: If supply and connections are correct but E4 persists, the electronic control board power supply section may be faulty and the board should be replaced.