Seat Altea Diesel Fuel Filter Heater Issue

Reduced engine power and uneven idling suggest fuel starvation. Have you checked the fuel filter? A clogged filter could cause those symptoms, especially with a diesel engine. When was the last replacement? If it's been a while, that's a good place to start. Though, a faulty heater is definitely possible. Does the error code point specifically to the heater circuit?

The error code points to the fuel filter heater. I know where the fuel filter is, but I'm not sure how to check the heater itself. Is there a way to test the cable or plug connection without special tools?

If the error code is specific to the heater and you're experiencing those symptoms, it sounds like the heater circuit is the culprit, as you suspected. Testing it properly usually involves a multimeter to check for voltage and continuity. Since you're unsure, I'd suggest taking it to a workshop. Messing with the fuel system without proper knowledge can be risky. It's probably a simple fix like a corroded connection, but best to be safe.

You were right. The shop found a faulty cable and plug connection on the fuel filter heater. They replaced it for 95€, and the car runs great now. Thanks for the help.