Seat Formentor Diesel Cold Start Issue

Sounds like a pain. I had a similar temperature control issue with my old Renault Megane. Heat not working properly in the cold start phase. Have you checked the blower motor resistor? Sometimes that can cause heating system problems, though I'm not sure if it would trigger an error code.

Thanks for the suggestion. I haven't checked the blower motor resistor specifically. Where is it usually located, and is it something I can test myself without special tools?

To be honest, I didn't check it myself. I just took it to the mechanic. But from what I remember, the blower motor resistor is often near the blower motor itself, usually under the dash on the passenger side. Given the error code and other symptoms, it really sounds like the heater itself is the problem. Probably best to get it checked out by a professional, just to be safe.

I took my Seat Formentor to the workshop, and they confirmed it's a defective electric auxiliary heater. The heater repair will be around 350€. Hopefully, this resolves the poor engine running, higher fuel consumption and the error message.