Smeg oven display shows Er03 and the door will not lock for pyrolytic self-cleaning.

Safety first: Disconnect the oven from mains power. Do not attempt to force the door closed or locked.

• Inspect the door latch: Open the door and examine the metal latch hook at the top or side. Check for bending, looseness, or obstruction. Tighten any loose screws and remove debris.
• Access the lock assembly: Remove the top panel or front control panel (depending on model) to reach the door lock motor assembly. It is usually mounted near the top front of the oven cavity.
• Check wiring and switches: Inspect the harness from the lock to the main control board for damage. Many Smeg locks have one or more microswitches that signal locked/unlocked status. Test each switch with a multimeter for proper open/closed operation when the lock lever is moved by hand.
• Test the lock motor: With power disconnected, measure the resistance of the lock motor coil. An open circuit indicates a failed motor. If you are experienced and can work safely, you may briefly power the motor with an appropriate test voltage to confirm movement, but this is best left to professionals.
• Replace faulty components: If the lock motor or microswitch is defective, replace the complete door lock assembly with a Smeg-compatible part. Reassemble, restore power, and test the pyrolytic cycle. If Er03 persists, the main control board output to the lock may be faulty.