C4 I directional headlamp ECU

[GiveMeABreak]

You'll have this if you have SEDRE - those designations are the PIN numbers in the 32 bit connector concerning the comms and power. I haven't included all the ones from the headlamps themselves or the height correctors as these won't be relevant given that the lights are working and that your issue is a communication one to and from the ECU - so that will either be because the ECU is not powered up, not earthed or the CAN wiring is faulty I suspect.

[Cutac]

Problem solved, it was the fuse. But for some reason, the manual that came with my car shows a different fuse layout. Fuse F6 was the culprit, but my manual says it's a fuse for the automatic transmission (which I obviously don't have).

[GiveMeABreak]

I didn't mention the fuse as F6 was listed for Halogens and Auto Transmission as you said - but that's typical of PSA!

[Cutac]

Can't believe it!
But hey, all that matters is that my headlamps work properly now

Thanks for your help, Marc!