DS4 rough running cold starts

Rough running and higher fuel consumption definitely sound like a malfunctioning PTC heater could be the culprit. It's like trying to run a marathon with a clogged air intake. Does the blower motor seem to be working correctly? If the heating element is failing, it might be drawing excessive current or simply not functioning, impacting the engine's warm-up cycle and overall efficiency. Have you checked the relevant fuses?

Thanks for the quick reply! The blower motor seems to be working fine, all speeds seem normal. I haven't checked the fuses yet, but I will. If the fuses are okay, is there a way to further confirm the heating element itself is faulty before I start tearing things apart? Is there a way to test the electrical current going to the heater?

If the fuses are good and the blower is working, it really does point strongly towards the heater itself. A multimeter could check the current, but honestly, fiddling with electricals can be risky if you're not totally comfortable. Given the symptoms and error code, and the fact you're looking at a potential electrical fault in the heating system, it's probably time to get it checked at a workshop. Could save you a bigger headache and potential damage.

Thanks a bunch for confirming my suspicions and providing that extra nudge. Took it to a trusted mechanic, and you were spot on – the electric auxiliary heater was indeed defective. 350€ later, it's fixed. Runs like new now. Much appreciated!