Volvo V40 rough running cold PTC heater issue

Sounds like it could be. A faulty PTC heater on those Volvos can definitely cause poor cold starts and increased fuel consumption since the engine is trying harder to warm up. Does your blower motor seem to be working okay?

The blower motor seems fine, yeah. If the PTC heater is defective, is replacement the only option, or is there something else I should check first?

Given the symptoms and the error code, a defective electric auxiliary heater is highly likely. You could check the wiring and connections to the heater, but honestly, at that mileage, it's probably just worn out. I'd recommend getting it checked at a workshop to confirm and get a quote for replacement.

Thanks for the advice. I took it to a workshop, and they confirmed it was the PTC heater. Cost me about 350€ to get it replaced, but it's running much better now.