XC70 Reduced Engine Power

Fuel filter heater, huh? Never heard of that causing reduced power. Are you sure you're not getting other codes? A bad fuel filter itself can cause problems. Have you changed it recently? Could be a clogged fuel line starving the engine, too. Definitely check that connection, but don't rule out the basics.

I thought about the fuel filter itself. I changed it about 20,000 km ago, so it shouldn't be that, but anything is possible. No other codes are popping up, just the one related to the fuel filter heater circuit. If it's just for cold starts, why is it affecting engine power now and the idling?

Okay, only that code is weird, especially since it's not winter. A faulty heater shouldn't mess with driving so bad. If you are sure the connections are clean, it sounds like it is shorting something. Honestly, for something like this, going to a shop might be best. They can properly diagnose the electrical system.

I checked the connector, and it looks fine, so it may be time to give it to the experts. I've booked it in for a proper diagnostic check at the local shop. The repairman found a broken wire in the cable harness. Fitting the new harness came to 95€, so I'm pleased with that. Many thanks for your help!