Seat Altea Diesel Heating Issue Resolved

I had a similar problem with my Altea. If the heating isn't working well and there's a cooling system error code, the water valve is likely the cause. Also, check the engine coolant level. Did you check the wiring and connections to the valve?

Yes, the coolant level is okay. When you checked the wiring, did you get the same 'cable or plug connection defective' error? Was the problem obvious, such as a broken wire, or something less noticeable?

That error message sounds familiar. I had a corroded connector on the water valve. It wasn't obvious at first, but there was green corrosion upon closer inspection. Considering the error and your symptoms, having a workshop diagnose the cooling system might be wise.

I wanted to let you know that the workshop visit confirmed the water valve issue. The cable connection had corrosion. After cleaning and valve replacement, the heating is back to normal. The cost was 95€. Thanks for the assistance!