Mini Cooper ventilation problem

Low heating output and an error code definitely points to a problem in your ventilation system. The air distribution flaps direct the airflow to where it's needed windshield, footwell, or face vents. If a flap is stuck, it can reduce the overall heating or cooling effectiveness. Have you checked the blower motor? If the blower motor resistor is faulty, it can affect the fan speed and airflow but you would have mentioned it. A defective cable could also be the culprit, as you suspect. Are you comfortable checking the wiring and connections yourself? Do you hear any unusual noises when you adjust the ventilation settings, like a clicking or grinding sound?

I am not familiar with the ventilation system components. Could you please elaborate on how to check the wiring and connections of the air distribution flap?

Okay, I understand your hesitation to dive into the wiring. Given the stored error and your symptoms, it's almost certainly a problem with the air distribution flap motor or its wiring, specifically for the defrost function. Air distribution flaps are essentially doors inside your ventilation system that control where the air goes. These flaps are moved by small electric motors. A defective motor or a break in the wiring harness to the motor can cause the flap to get stuck. I suggest taking it to a qualified workshop to diagnose and repair the issue. Your initial suspicion of a cable or plug connection being defective is very likely the cause.

Thank you for the information. I took the vehicle to the workshop, and the defective cable/plug connection of the air distribution flap was repaired as you suspected. The total cost was 95€.