If the power door lock switch does not operate electrically, the only way to lock the door(s) is with the mechanical key from the outside key hole.
You can lock the doors without the outside key hole as follows:
1. Open the door.
2. Insert the key into the emergency door lock hole and turn the key horizontally to lock.
3. Close the door securely.
Kia Cee'd JD Service Manual: Front Seat Assembly Components and components location
Component Location
1. Front seat assembly
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Kia Cee'd JD Service Manual: DC DC Converter Repair procedures
Removal
1.
Disconnect the battery negative terminal.
2.
Remove the glove box housing.
(Refer to Body - "Glove Box Housing")
3.
Disconnect the DC/DC converter conector (A).
4 ...