Seat Tarraco Diesel Rough Running Cold

I had a similar issue with my older Volvo V70. Same symptoms: reduced power, rough idle, and an error code related to the fuel system. In my case, it turned out to be a faulty fuel temperature sensor. Have you checked that?

Fuel temperature sensor, eh? Whereabouts is that located? And is it something I can check myself with a multimeter, or is it best left to a professional?

Yes, the fuel temperature sensor is often integrated with the fuel filter assembly. While you could check the resistance with a multimeter, interpreting the readings can be tricky without the proper specs. Given your symptoms and the error code, a faulty connection on the fuel filter heater is the most probable cause as you mentioned in your initial post. I'd suggest getting it checked by a professional to confirm and avoid further damage to the fuel system.

Took the Tarraco to the shop, and you were spot on. They found a dodgy connection on the fuel filter heater. 95€ later, it's fixed. Thanks for the help.