Ariston Oven Error Code ER04

ER04 means the oven's control system was unable to unlock the door, indicating a door lock mechanism failure. The oven sent the unlock command but did not receive confirmation that the lock completed its travel to the open position. This can involve the lock assembly itself, the wiring circuit, or the power supply board.

A power reset by unplugging the oven or cycling the circuit breaker may temporarily clear the code, but if the underlying lock mechanism or circuit fault remains, ER04 will return the next time the door lock is activated. A reset alone does not repair a faulty lock assembly or wiring issue, so the root cause must be addressed to permanently resolve the error.

Repair costs vary depending on the failed component. Replacing the door lock assembly typically falls in the range of $80 to $200 including parts and labor, while replacing the power supply board can range from $150 to $350 or more depending on parts availability. A diagnostic service call alone may cost $60 to $120, which is often applied toward the final repair.

A knowledgeable DIYer can start by inspecting the door lock area for visible obstructions, debris, or obvious wiring damage, which require no parts. However, testing the lock circuit for continuity, checking connector integrity, and replacing the lock device or power supply board are tasks that involve working with electrical components and are best handled by a qualified technician if you are not comfortable with appliance wiring.

You should not continue using the oven while ER04 is active. If the door is locked and cannot be released, attempting to operate the oven creates a safety risk and could make diagnosis more difficult. Stop use, disconnect power if possible, and have the door lock mechanism inspected before resuming operation.